Patterns of Heredity
Name:______________________________________Period:____Date:____________
 _______all traits are simply inherited by dominant and recessive alleles (Mendelian
Genetics). In some traits, neither allele is dominant or many alleles control the trait.
Below are different ways in which traits can be inherited from parents to offspring.
5 Different Modes of Inheritance:
1. __________________________________:
 Definition:
 Neither allele for a gene ___________________

Phenotype of the heterozygous offspring will be a _________of the 2
homozygous parents.
 Ex: A ___________________white flower crossed with a
_________________red flower will produce all
_____________________pink flowers.
Homozygous
Parent
Heterozygous
OFFSPRING
Homozygous
Parent
 Notation:
 Alleles are all capital letters because NEITHER one _________________ the
other. So one of the alleles has a ____________( ‘ ) on it to represent an
alternate expression of the gene.

Always make a _______to show the genotypes and the resulting phenotypes.
 Still supports Mendel’s Law of Independent Assortment
Ex. 1) In a certain species of flowers, snapdragons, the combined expression of both alleles for
flower color produces a new phenotype-pink. A red snapdragon is homozygous and is crossed with a
homozygous white snapdragon. What are the genotypic and phenotypic ratios of this cross?
Key:
P Cross = _________ x ________
Genotype:
Phenotype:
1
Ex. 2) Then cross the F1 generation and what are the genotypic and phenotypic ratios of this cross?
P Cross = _________ x ________
Key:
Genotype:
Phenotype:
2. ________________________________
 Definition:
o Both ______________are expressed ____________________
o Phenotypes of heterozygous offspring are
showing both traits!

Ex: red cows crossed with white will
generate roan cows.
___________refers to cows that have
red coats with white blotches.
 Notation:
o 2 ________________alleles (capital letters) are used
o Always make a _____ to show the genotypes and the resulting phenotypes
Ex. 1) In chickens, black-feathered is not wholly dominant over white-feathered, so heterozygous chickens
are black and white checkered. Cross two heterozygous chickens. What would the appearance of their
offspring be?
P Cross = _________ x ________
Phenotypes:
Key:
Ex.2) In shorthorn cattle, the hybrid between red and white is called a roan. What phenotypes would result
in the cross of a roan and a white?
P Cross = _________ x ________
Phenotypes:
Key:
2
3. ________________________________
 Definition:
o More than _______________for a single gene can control a trait.
 Multiple alleles must be studies by looking at the entire population of species.
 Each individual carries only 2 alleles for any gene (one on each homologous
chromosome).
o In this form of inheritance, a trait can have 1 gene, but ______________
for that gene.
 Ex: The human blood group can be any combination of A, B, and O
o The alleles are IA, IB, and i

Alleles A and B are __________________________

Alleles i (“O”) is ____________________________
 Notation:
o The possible genotypes/phenotypes:
GENOTYPES
PHENOTYPES
Homozygous type A
I AI A
type ____blood
Heterozygous type A
I Ai
type ____blood
Homozygous type B
IBIB
type ____blood
Heterozygous type B
IBi
type ____blood
Codominant type AB
I AI B
type ____blood
Recessive type O
ii
type ____blood
o NOTE: the “i” is dropped from the genotype of A and B when the
______________________is written. (Genotype IAi is type ____ blood)
o Interesting facts:
 In the U. S., about 45% of the population is type O, 42% type A,
10% type B, and only 3% type AB.
3




The positive and negative of a blood type is called
the__________________, it is a totally separate ________with
Rh+ (RR or Rr) and Rh–alleles (rr)
o If you have the protein = Rh +
o If you DO NOT have the protein = Rh –
In the U. S., about 85% of the population is Rh+ and 15% Rh–.
Thus the chances of someone being O- [having both ii and rr] would
be 45% × 15% = 6.75%.
The most rare blood type would be _______, about 0.45% of the
population.
 _____is the universal donor
 ______is the universal receiver
Ex.1) If a person of blood group AB marries one belonging to group O, what could be the possible
genotypes and phenotypes of their offsprings’ blood types?
Genotype:
P Cross = _________ x ________
Phenotype:
Ex.2) If a father is homozygous blood type A and the mother is heterozygous blood type B. What
could be the possible genotypes and phenotypes of their offspring’s blood types?
Genotype:
P Cross = _________ x ________
Phenotype:
4
 2 Types of Chromosomes:
1. _____________________- last pair of chromosomes—23rd pair for humans
XX = _________________
XY = _________________
2. ______________________________or _____________– all other pairs of
chromosomes – 1-22nd pair in humans
4.________________________: (X-Linked)
 Other genes besides the alleles for sex are located on sex chromosomes.
 Definition:
o These traits will occur _________frequently in males than females, such as
color blindness and hemophilia.
 WHY?
o Alleles for a gene may be present on the X chromosome but
_______on the Y. These are called sex-linked genes.
o This means that _________may inherit just ______allele for a
characteristic and that allele will be expressed, whether it is
dominant or recessive, because it is the ________allele present on
their X chromosome.
o X-linked traits most likely will be _______________to the normal
condition and the Y chromosome lacks the gene for a trait, so males
have a higher chance of having the disorder.
 These traits generally do NOT show up in ______________ since females have
genes on both their X chromosomes.
 Notation:
o The alleles for these traits are written as ____________________on
the ____chromosome ONLY.
o ____ alleles are written on the Y chromosome!
 Ex: Colorblind male = XbY and Normal male = XBY
o _________________FEMALES are known as___________, XBXb
5
Ex.1) Color blindness is a sex-linked trait that is caused by a recessive allele. A colorblind man
marries a woman that is homozygous for normal vision.
 What possible types of vision could be found if they had boys? ____________________

What possible types of vision could be found if they had girls? ____________________
P Cross = _________ x ________
Ex.2) A girl of normal vision, whose father was colorblind, marries a colorblind man. What types of
vision could be found in their children?
Phenotype:
P Cross = _________ x ________
5. _________________________________
 Traits are determined by ____________________
 They may or may not be found on the same chromosome
 Each gene may have more than 2 alleles
 The phenotypes may vary depending on the number of dominant and recessive alleles
in the genotype
 Traits that show _____________________are a result of polygenic inheritance
o Ex: eye color, skin color, height, facial features
Environment & Genes:
 The____________________ can determine whether or not a gene is fully
expressed or expressed at all.
 Internal and external environments can affect phenotypes:
1. Influence of internal environment:
~ __________________based on sexes (testosterone, estrogen)
2. Influence of external environment:
~_____________________________
~_____________________________
~_____________________________
~_____________________________
~_____________________________
All of these can
influence the
expression of
genes.
6
Genetic Mutations:
How Genetic Mutations Can Affect The Human Body
Name: _______________________________________________Period:_________
The genetic information (DNA) in our cells plays a major role in how our body works. Spelling mistakes
often happen when this information is being transcribed. When these spelling mistakes occur on uncoded
genes, there aren't any consequences. In a few rare cases, however, a spelling mistake – or mutation can have serious implications.
Meet Ziad, Maria, and Nicholas. They all live with the consequences of mutations in their genetic code.
You will see that sometimes these mutations can cause an illness like diabetes, a handicap like
colorblindness and even resistance to a disease like AIDS. Read each of these three scenarios and then
describe in a few lines each person's daily life.
Scenario 1 - Ziad
Ziad was born with poor eyesight: he is color-blind. His mother genetically passed down this disorder to
him, and yet she does not suffer from color-blindness herself. How can that be? Well, Ziad's particular
type of color-blindness (the inability to distinguish between red and green) is the most common kind and
is caused by a genetic defect on the x chromosome.
Since he can't rely on color to help him go about his daily activities, Ziad has to find other ways of coping.
How do you think he manages? To help you answer this question, try to imagine what Ziad has to do to
dress himself properly, find the family car in a parking lot, identify insects for his collection or choose
fresh fruit and vegetables at the grocery store.
Ziad’s daily life: ______________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
Scenario 2 - Maria
Maria suffers from diabetes. Because her pancreas doesn't produce insulin, Maria can't control the amount
of sugar in her bloodstream. Insulin is very important because it helps our bodies efficiently use the
energy in the food we eat and keeps our bodies in good working order.
Unfortunately, there is no cure for diabetes, but the disease can be controlled. To do so, Maria has to
inject herself with insulin before each meal. She can never skip meals and she must always keep a few
healthy snacks on hand, especially before and after strenuous physical activity. Maria is a very active
teenager. She plays soccer twice a week after school and she also sings with the school choir twice a
week. At the moment she is planning a two-week family vacation to South America to visit her
grandparents. What precautions do you think Maria has to take if she wants to do all these activities
without any difficulty?
Maria’s daily life: ______________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
7
Scenario 3 – Nicholas
Nicholas has been a heroin addict for several years now. Despite his doctor's frequent warnings, Nicholas
still shares needles with other heroin addicts. This is dangerous because when needles are shared, the
contaminated blood of a person infected with the HIV virus, or other diseases, can be transmitted to
another person. The HIV virus can eventually cause AIDS, where a person's immune system breaks down
and they become highly susceptible to a range of illnesses, including some that can cause death.
Currently there is no cure for HIV or AIDS.
One day, a friend Nicholas had shared needles with told him he had AIDS. Worried and convinced that he
was infected too, Nicholas decided to get tested. He and his doctor learned that he had in fact contracted
the HIV virus. Several years went by and Nicholas still did not develop AIDS, so he and his doctor decided
to do some more medical tests. The HIV virus can stay in the human body for several years without any
signs of illness: this is the HIV-positive period. The disease can show itself as early as two years after
being infected by the HIV virus or as late as ten years. They discovered that Nicholas' genetic code
contained two mutant copies of a certain gene. Luckily, this mutation protects the cells against attacks by
the HIV virus. Less than 1% of Caucasian, or white, males have this mutation. Thanks to this mutation,
Nicholas will spend the rest of his life without ever developing AIDS, although he will still be a carrier of
the HIV virus and he could infect others.
In this case, the mutation had a positive effect on someone's health. Use your imagination to think up
beneficial genetic mutations that would make humans even better. You can use super-heroes like
Superman as your inspiration.
Nicholas’s daily life: ____________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
8
GENETIC CHANGES: MUTATIONS
Name:_________________________________________Period:_______Date:___________________
MUTATIONS
Translocation
Inversion
Nondisjunction
Insertion or Deletion
Frameshift
mutation
Point
mutation
VOCABULARY:
o ________________________= a random error or change in the DNA sequence that
may affect whole chromosomes or just one gene.
o _______________________= certain substances or conditions that can create a
greater rate of mutation
 Examples:
 Some _______________
 High temperatures
 ______________________
 Radiation
CHROMOSOMAL MUTATIONS: changes in chromosomes, usually during
meiosis when gametes are being made:
1. ___________________________= failure of homologous chromosomes to separate
during meiosis resulting in gametes (egg or sperm) with too few or too many
chromosomes.
 REMEMBER: Humans are ___________creatures; meaning for every
chromosome in our body, there is another one to match it.
 ________________= abnormal number of chromosomes. Ex: trisomy,
monosomy
9

____________________= zygote contains three copies of the
chromosome.
o Ex: Down syndrome, Klinefelter’s (XXY)
 _____________________= zygote contains only one
chromosome of the pair i.e. it is missing one chromosome
2. _____________________= occurs when part of a chromosomes is missing.
3. _____________________= occurs when a part of a chromatid breaks off and
attaches to its sister chromatid. The result is a duplication of genes on the same
chromosome.
4. ________________________ = Segment of chromosome breaks off and is
reinserted backwards (will flip upside down)
5. ______________________ = occurs when part of one chromosomes breaks off and is
added to a different chromosome.
GENE MUTATIONS: changes in the DNA sequence that will then change the
amino acid sequence. (Remember: Amino acids make up our proteins!)
1. __________________________= a change in a single base pair in DNA.
2. _________________________= error in the DNA sequence that adds or deletes a
single nitrogen base, causing nearly all amino acids following the mutation to be changed.
 Types:
 _______________________= One nitrogen base (A, T, C or G) is
deleted from the DNA sequence.
 ________________________= Extra nitrogen base is added to the
DNA sequence.
10
Name:______________________________________Period:_____Date:_______
 ______________________= a valuable tool for anyone working in the field of genetics.
 Used to show ____________________in families, and resemble a____________.

Circles represent ______________, and squares represent ___________.

__________________________are represented by roman numerals on the ______ side
of the pedigree.

_____________ is represented by a __________ through the symbol

Lines that connect circles and squares horizontally represent that
_____________________ has occurred.

The further to the _____________an individual is the __________they are.

Any vertical lines that drop down from the center of the above horizontal line show the
______________________ of the parents.
I.
II.

We can then mark offspring that _____________or _______________exhibit certain
characteristics, such as eye color.
Ex: The following pedigree shows family members with blue eye color.
I.
II.

Brown eyes (B) are dominant over blue eyes. We can deduct the genotypes of some family
members. Try to predict what the genotypes of the above family are for eye color.
A. What is the genotype of the mother? _______
B. What is the genotype of the son? _________
C. Can you deduce from the above information what the genotype of the father is? _______
How do you know?
__________________________________________________________
11

Now let’s discuss the story of sickle-cell anemia. In Africa, there is a high incidence of
malaria. Malaria is caused by a parasite that is transmitted by mosquitoes. The parasite
feeds on the hemoglobin protein in red blood cells. If there is mutated strain of hemoglobin
in the red blood cells, the parasite starves to death and dies. The picture on the left shows a
sickled red blood cell and the picture on the right show a normal red
blood cell.
Persons who are homozygous for normal red blood cells easily die from
malaria. Persons who are homozygous for mutated red blood cells
usually do not die from malaria, but could die from complications
resulting from their odd shaped red blood cells (sickle-cell anemia). Individuals heterozygous
also usually do not die from malaria and are spared from the awful complications of sicklecell anemia.

Using the following information, design a pedigree chart and designate which of the family
members is homozygous for normal hemoglobin (HH), heterozygous (Hh), and homozygous
recessive (hh).
~Mom-survived malaria
~Dad- died from complications from sickle-cell anemia at age 42.
~Son #1- survived malaria
~Son#2- Survived malaria, has sickle-cell anemia
~Daughter #1- survived malaria
Make A KEY:
I.
hh =
Hh =
II.
HH =

If the daughter marries a man who has normal hemoglobin (HH) in his red blood cells, what
is the probability that their children will have sickle-cell anemia? ______ out of ______.

Would their family be wise to take drugs that prevent a person from dying if infected with
the malaria parasite? Why?
___________________________________________________________________________
12

Nearsightedness is a recessive trait (n). The shaded
regions show individuals who are recessive for
nearsightedness.
Now you construct a pedigree! Left-handedness (h) is a recessive trait.
Bill and Mary have a son, Mike, and daughter, Sue (youngest) that are
right-handed. They also have a middle daughter, Marie that is a lefty. Sue
gets married to John (righty) and has three children. Their oldest daughter,
Sarah and their middle son, Joe are right handed. Yet, their youngest son,
Ryan is a lefty.
1. Label the generations and label each individual in the pedigree by placing
their name below the shape.
2. Determine the genotypes of as many individuals as possible.
13
Human Karyotypes
I. What Is A Karyotype?

_________________________________ = a test to identify and evaluate the size,
shape, and number of chromosomes in a sample of body cells.
o Homologous chromosomes are arranged by ____________, ______________
patterns, and _____________________ placement.
o Extra, missing, or abnormal positions of chromosome pieces can cause problems
with a person's growth, development, and body functions.
o 2 types of chromosomes:

___________________(autosomes) = chromosome pairs 1-22

Sex = __________chromosome pair; determines the sex of the individual
o Examples:
Normal __________
Normal __________
II. Why Is It Done?
1) Determine whether the chromosomes of an adult have an ____________________that
can be passed on to a child.
2) Determine whether a chromosome __________________is preventing a woman from
becoming pregnant or causing miscarriages.
3) Determine whether a chromosome defect is present in a fetus.
4) Determine the cause of a baby's birth defects or disability.
5) Identify the __________ of a person by determining the presence of the Y chromosome.

This may be done when a newborn's sex is not clear.
III. How Is A Karyotype Created?
1) Human karyotypes are usually prepared from ____________________________of
chromosomes that have been spread, fixed, and stained to highlight banding patterns.
14
2) The chromosomes in the photograph are ____________________ and then arranged in
homologous pairs just as you will be doing in an upcoming activity.
3) Chromosomes are obtained through various tests: blood, bone marrow, amniotic fluid, or
tissue from the placenta (the organ that develops during pregnancy to feed a growing
baby).

White blood cells are used most frequently because they are easily induced to divide
and grow in culture.

To test amniotic fluid, an _________________________________is done. A long
needle is inserted through the abdomen into the uterus and amniotic fluid is
withdrawn which contains cells shed by the fetus.

A bone marrow specimen requires a bone marrow biopsy.
4) The sample is placed into a special dish and allowed to grow in the laboratory.
5) Various _______________ are added to stop the cell’s growth during prophase and
metaphase.
6) The cells are placed on microscope slides and treated so they swell and their
chromosomes spread apart.
7) Then various ______________ are used to highlight banding patterns.
8) The treated chromosomes can then be photographed, enlarged if desired, and ______
_______ to do a karyotype.
9) Experienced geneticists observe the karyotype for chromosomal abnormalities.
IV. What Are Genetists Looking For?
1) Differences in ____________ of chromosomes

Missing pieces or additional pieces
2) Differences in the position of ________________________

This is brought about by translocations.
3) Differences in basic ______________ of chromosomes
V. Common Abnormalities:
1) Down Syndrome (also known as
______________________)

Cause = nondisjunction of the ______________of

Characteristics:
chromosomes
o
Happens _____________ in males and females
since it does not involve the sex chromosomes
o Individuals are mentally handicapped but the
severity varies with the individual.
o The probability of giving birth to a child with Down syndrome ______________
with age of the mother, increasing significantly after age 35.
15
2) Turner syndrome

Cause = nondisjunction of the
______________________during meiosis so individuals are
missing one copy of the ____chromosome.
o They have 22 pairs of autosomal chromosomes and
only one X chromosome.

Characteristics:
o Affects ONLY _______________
o Women are usually short, sexually underdeveloped
and sterile.
o Women with this syndrome function well within society and are not diagnosed
until they are assessed for infertility as adults.
3) Klinefelter syndrome (XXY)

Cause = nondisjunction of the ____________________________during meiosis so
individuals have an extra ___ chromosome
o

The person has 22 autosomal chromosomes and 3
sex chromosomes (XXY).
Characteristics:
o Affects ONLY ____________
o
Males are often tall, sexually underdeveloped and
may have slight intellectual impairment.
o Recognition of this syndrome before puberty usually
does not occur.
o Many males with this syndrome function well within
society and are not diagnosed until they are assessed for infertility as adults.
4) Jacob's syndrome (XYY)

Cause = occurs when a male inherits ________ Y chromosomes from his father
instead of one. The exact cause of why this occurs is
unknown.
o Individuals with Jacob’s syndrome have 22
autosomal chromosomes and 3 sex
chromosomes (XYY).
o He is an __________male. Remember most
males are XY.

Characteristics:
o Affects ONLY_______________
o The most common symptoms are learning problems at school and delayed
emotional maturity.
o
Males are tall, thin, have acne, speech problems, and reading problems.
16
Codominance & Incomplete Dominance Practice Problems
 Directions: Use a Punnett square to answer the following problems. Show all work to receive
full credit. You should include keys for you Punnett squares!
1. What is the difference between a trait that shows codominance and a trait that show
incomplete dominance?
2. How do you notate a Codominance Inheritance pattern?
3. How do notate an Incomplete Dominance inheritance pattern?
4. Nose size is a trait that exhibits incomplete dominance. Larger noses are not dominant over
small noses. If both parents have a medium size nose, do they have to worry about any of their
children having a large nose?
a. What are the genotypes of the parents?_______________________
b. List the genotypic & phenotypic ratios of the children below.
c. What % of this couple’s children will have large noses? _________________
Key:
5. Coat color is a trait that exhibits codominance. If a roan colored cow mates with a cow with a
white coat, what will the offspring look like?
a. What does the term “roan” mean?__________________________________
b. What are the genotypes of the parents? __________________________________
c. List the genotypic & phenotypic ratios of the offspring below.
Key:
17
6. Bark texture can be a codominant trait, producing trees with bark that is smooth, rough, or
both smooth/rough. If a rough barked tree pollinates a tree that is smooth/rough, will any of
the new saplings have smooth bark?
a. What are the genotypes of the parent tress?_____________________
b. List the genotypic & phenotypic ratios of the offspring below.
c. What % of the saplings will have smooth bark?____________________
Key:
7. A black haired female and a blonde male have four children, all of whom have brown hair.
a. What condition makes this possible?_________________________________
b. What are the genotypes of the parents?______________________________
c. What are the genotypes of the offspring?_____________________________
d. Are the parents heterozygous or homozygous?__________________________
e. Are the offspring heterozygous or homozygous?________________________
Key:
8. A florist has a big demand for pink carnations, so he breeds pink carnations in an attempt to
produce more pink carnations. However, when his new plants bloom, only 50% of the flowers are
pink. (The remaining 50% are red or white).
a. How did this happen? (show the Punnett square)
Key:
b. What must the genotypes of the parent plants be?______________________
c. What must the genotypes & phenotypes of the parent plants be in order for 100% of the
flowers to be pink? ___________________________
18
SEX-LINKED TRAITS
Name:_______________________________________________Period:__________Date:__________
1. Use the key to determine the genotypes of the following people.
B = normal vision
H = normal blood
h = hemophilia
b = colorblind
a. Female w/ normal vision ____________
f. Female w/ normal blood _________
b. Male w/ normal vision ______________
g. Male w/ normal blood __________
c. Colorblind female ____________
h. Female w/ hemophilia _________
d. Colorblind male ____________
i. Male w/ hemophilia _________
e. Carrier of colorblindness ____________
j. Carrier of hemophilia _________
2. A woman who is colorblind marries a man with normal vision.
a. What are the genotypes of these parents?_________________________
b. Show the Punnett square below.
c. What are the genotypes and phenotypes of the offspring?
d. What % of the children will be colorblind? ______________
3.
A man with hemophilia and a woman who carries the genes for the disease want to have children.
a. What are the genotypes of these parents?__________________________
b. Show the Punnett square below.
c. What are the chances that their children could have hemophilia?________________________
19
4.
If a carrier female for hemophilia marries a normal male:
a. What are the genotypes of the parents?____________________________
b. Show the Punnett square below.
c. What are the chances of the offspring having the disease hemophilia?_____________
d. What are the chances of their sons being normal?________________________
e. What are the chances of their daughters being carriers?____________________
5.
If a woman’s father had hemophilia, what are the chances that she is normal? Assume that
you do not know the mother’s phenotype.
6.
If a woman’s mother was a carrier, what are the chances that she is normal? Assume that
you do not know the father’s phenotype.
7.
Are you more likely to be affected by a sex-linked disease if you are a male or a female?
Explain why.
20
Multiple Alleles
A. Blood types are an example of what type of inheritance?______________________________
B. In blood, the gene for type A and the gene for type B are______________________________.
C. The gene for type O is_____________________________.
Directions: Using Punnett squares, determine the possible blood types of the
offspring when:
1. Father is type O, Mother is type O
_______ % O
_______ % A
_______ % B
_______ % AB
2. Father is type A, homozygous; Mother is type B, homozygous
_______ % O
_______ % A
_______ % B
_______ % AB
3. Father is type A, heterozygous; Mother is type B, heterozygous
_______ % O
_______ % A
_______ % B
_______ % AB
4. Father is type O, Mother is type AB
_______ % O
_______ % A
_______ % B
_______ % AB
5. Father and Mother are both type AB
_______ % O
_______ % A
_______ % B
_______ % AB
21
Mode of
Inheritance
Define
Notations

Neither allele for a
gene dominates so
the hybrid
phenotype is a
_____________of
the homozygous
parents

Alleles are all capital
letters because
_________________
one dominates the
other.
One of the alleles has
a prime ( ‘ ) on it to
represent an alternate
expression of the
gene.
Example


KEY:
Red = _________
White = _____________
Pink =_____________

Both alleles are
expressed
_______________

2 _______________
capital letters (alleles)
are used
A homozygous white flower is
crossed with a homozygous red
flower and produces all pink
flowers.
Blended trait is the ____________
A black chicken is crossed with a
white chicken and black and white
checkered chickens are produced.
KEY:
Black = _________
White = _________
Checkered = __________
BLOOD TYPES
 Type O = _______

More than 2
______________for
a single gene can
control a trait


Traits are carried
on the
_____chromosomes

______ & _____ are
codominant
o Use capital ”I”
with superscripts
for specific allele
______ is recessive
o Use lowercase “i”
 Heterozygous Type A = _______
The alleles for these
traits are written as
superscripts on the
_______chromosome
ONLY.
COLORBLINDNESS,HEMOPHILIA
__________alleles
are written on the Y
chromosome!
 Normal female = XBXB, XBXb
 Homozygous Type A = ________
 Type AB = _________
 Heterozygous Type B = ________
 Homozygous Type B = ________
 Colorblind male = XbY
 Normal male = XBY
 Colorblind female = Xb Xb
 __________________ = XBXb
22
Different Modes of Inheritance Problems
 Directions: Determine the possible genotypes and phenotypes for each cross. Be sure to use the
correct notation and create a genotype key when necessary.
1. Colorblindness is a sex-linked recessive trait (b). If a female carrier marries a male with normal
vision, what are their chances of having a colorblind child?
a. What type of inheritance makes this possible?________________________________
2. A cross between a homozygous red-flowered snapdragon and a homozygous white-flower snapdragon
produces all pink snapdragons. Complete the Punnett square for a cross between a pink snapdragon
and a white snapdragon.
a. What type of inheritance makes this possible?________________________________
Key:
3. A person that has type O blood marries a man that is heterozygous for type B blood. What are the
possible blood types of their children?
a. What type of inheritance makes this possible?________________________________
4. A cross between a homozygous black chicken and a homozygous white chicken produces all backand-white checkered chickens. Complete the Punnett square for a cross between two checkered
chickens.
a. What type of inheritance makes this possible?________________________________
Key:
23
MUTATIONS ACTIVITY
Name:_____________________________________ Period:______Date:________________
Procedure: How do gene mutations affect proteins? CAREFULLY follow the directions
below.
This is the ORIGINAL DNA STRAND:
TAC GCC AGT GGT TCG CAC
1. Transcribe the original DNA strand into a strand of mRNA. Using the table provided, determine the
order of amino acids that the original strand of DNA is coding for. The combination of these amino
acids forms a protein fragment. Write out the amino acids in order.
DNA:
___________________________________________________________________________
mRNA:
___________________________________________________________________________
Amino Acids:_________________________________________________________________________
2. Change the fourth base in the original DNA strand from G to C.
a. Write out your NEW DNA strand
b. Transcribe this new DNA strand into its complimentary mRNA
c. Decode the mRNA using the table provided and write out the amino acids in order
d. Does the new protein fragment differ from the original one? Circle any differences.
DNA:
___________________________________________________________________________
mRNA:
___________________________________________________________________________
Amino Acids:_________________________________________________________________________
3. Add a G to the original DNA strand after the third base.
a. Write out your NEW DNA strand
b. Transcribe this new DNA strand into its complimentary mRNA
c. Decode the mRNA using the table provided and write out the amino acids in order
d. Does the new protein fragment differ from the original one? Circle any differences.
DNA:
___________________________________________________________________________
mRNA:
___________________________________________________________________________
Amino Acids:_________________________________________________________________________
Analysis:
1. When did a point mutation occur in the DNA strand? (Hint: what number of the procedure?)_______
2. When did a frameshift mutation occur in the DNA strand? (Hint: what number of the
procedure?)_________
3. How did the point mutation affect the protein fragment?
4. How did the frameshift mutation affect the protein?
24
Genetic Changes: Mutations Worksheet
Name:_______________________________________________Period:_______Date:____________
Complete the following outline using the words below:
chemicals
disorder
frameshift mutation
individual
mutagens
mutation
point mutation
radiation
shift
temperature
ultraviolet
variations
GENE MUTATIONS
I. 1. ______________________________________ is a permanent change in the genetic material
of a cell.
A. Mutations usually affect 2. __________________________________ genes.
B. Mutations provide the 3. ______________________________ that are the basis of changes in
a species.
II. Mutations are often caused by 4. ________________________________, which are substances
or conditions that cause or increase the rate of mutation.
A. Some viruses are mutagens.
B. Very high 5. ____________________________ are mutagens.
C. 6. ___________________________, such as pesticides and some food additives are mutagens.
D. 7. _________________________________ is a well known mutagens.
1. X rays can damage DNA.
2. Gamma rays can damage DNA.
3. Large amounts of 8. ___________________________________ light can cause premature
aging of the skin.
III. Mutation can occur in two basic ways.
A. 9. ___________________________________ is one way.
1. This is an incorrect substitution of a single as in a codon of a gene.
2. It may not cause a noticeable difference.
3. It may cause a genetic 10. ______________________________.
B. 11. ____________________________________ is another way.
1. This is when a nitrogen base is inserted or deleted and causes a 12. ___________________
of the genetic code.
2. This is generally more damaging than the mutation in IIIA.
25
Directions: In the following questions the boxes represent chromosomes. The chromosomes that are
shaded grey are normal chromosomes and the chromosomes following the arrow a mutation has
occurred. Identify each of the following types of chromosomal or gene mutations and briefly describe how
it is different from normal chromosomes (shaded grey) and what might be the result of the rearrangement
or abnormality.
1234567
1236547
13. Identification: ________________________________________________________________
14. Differs: _____________________________________________________________________
15. Possible results: ______________________________________________________________
12345
123de
abcde
abc45
16. Identification: ________________________________________________________________
17. Differs: _____________________________________________________________________
_________________________________________________________________________
18. Possible Results: ______________________________________________________________
1234567
12367
45
19. Identification: __________________________________________________________________
20. Differs: _______________________________________________________________________
21. Possible results: ________________________________________________________________
Directions: Define the conditions of the following terms.
22. nondisjunction __________________________________________________________________
_____________________________________________________________________________
23. monosomy _____________________________________________________________________
24. trisomy ________________________________________________________________________
25. aneuploidy _____________________________________________________________________
26
Interpreting Pedigrees
 Phenylthiocarbamide (PTC) gene- Can you taste it?
Background: In 1931, a chemist named Arthur Fox was pouring some powdered PTC into a bottle. When
some of the powder accidentally blew into the air, a colleague standing nearby complained that the dust
tasted bitter. Fox tasted nothing at all. Curious how they could be tasting the chemical differently, they
tasted it again. The results were the same. Fox had his friends and family try the chemical then describe
how it tasted. Some people tasted nothing. Some found it intensely bitter, and still others thought it tasted
only slightly bitter. Soon after its discovery, geneticists determined that there is an inherited component
that influences how we taste PTC. Today we know that the ability to taste PTC (or not) is conveyed by a
single gene that codes for a taste receptor on the tongue. The PTC gene, TAS2R38, was discovered in
2003 on chromosome 7.The ability to taste the chemical phenylthiocarbamide (PTC) is dominant over
the inability to taste it. Researchers use this discovery to help explain why some people love their leafy
greens while others simply can’t bear the bitter taste. In one series of studies, PTC tasters were more
sensitive to spicy and sweet foods and found fatty foods less appealing. They tended to avoid broccoli
and grapefruit juice, found spicy food painful and shunned fat. Let’s test your tastebuds! 
Procedure A : Phenylthiocarbamide (PTC) gene
1) Obtain a piece of PTC paper from your teacher. Chew on the paper and then discard it.
a) If you are a PTC taster you should be able to taste the bitterness right away. Remember, if the
paper tastes bitter that means you have the dominant trait but you may be homozygous (TT) or
heterozygous (Tt). You don’t really know. For now, simply record T? on the line, if you could
taste the paper. But if you cannot taste the paper, you have the recessive trait, so record “tt.”
Genotype: ______________
Diagram A: Pedigree showing individuals who cannot taste PTC.
I.
II.
2
1
3
4
6
5
III.
7
Directions: Answer the following questions using Diagram A.
1) What represents generations on a pedigree? __________________________________________
2) What represents males on a pedigree? ______________________________________________
3) What represents females on a pedigree? ____________________________________________
4) Who is the oldest in the 2nd generation? _____________
5) What is the relationship between individual I.-2 and III.-7? Be specific. ________________________
6) What is the genotype of individual I.-2? ____________
7) What is the genotype of individual II.-4? ____________
8) How would you notate that individual I.-1 died in the pedigree above?
27
Procedure B : Determining Genotypes From A Pedigree
1. Nearsightedness – or myopia – is a recessive trait. Use the symbols N and n to label the genotype for each of
the numbered individuals. The shaded regions show individuals who are homozygous recessive for myopia.
Diagram B: Myopia (Nearsightedness)
I.
II.
2
1
3
4
10
9
8
7
III.
6
5
IV.
12
11
13
2. Free ear lobes are a dominant trait. Attached earlobes are a recessive trait. Use the symbols E and e to
label each of the numbered individuals. The shaded regions show individuals who are homozygous recessive
for attached ear lobes. They exhibit the trait being studied; they have attached ear lobes.
Diagram C: Ear lobes
I.
1
2
A) Free
Ear lobes
II.
3
III.
5
IV.
6
7
Attached
Ear lobes
4
8
9
10
28
Analysis:
1. If the genotype, “R?” is used, what does that genotype represent?
______________________________________________________________________________________
2. Why would someone conduct a pedigree study?
______________________________________________________________________________________
3. If you were to do a population study in Enola, where do you think you would find the LEAST amount
of variation of phenotypes?
______________________________________________________________________________________
Going Further: A SEX-LINKED Pedigree
Hemophilia is a disease in humans that causes the blood to clot slowly. It is a sex-linked trait that is caused by a
recessive gene on the X chromosome. Label each of the numbered individuals Using H for normal blood clotting
and h for hemophilia. Remember to label both the X and Y chromosome.
Diagram D: Hemophilia
I.
II.
III.
IV.
2
1
3
7
4
8
5
9
6
10
11
29
Pedigree Analysis Worksheet
Part A: Determining Genotypes in a Pedigree
Gomez and Morticia Addams are expecting a new baby! They
have come to your genetic counseling firm to find out the probability
that he/she will have webbed feet, a trait that runs in the family.
1. Observe the following pedigree. Number the generations on
the pedigree.
2. Determine the genotypes of the individuals in the pedigree.
Write the genotypes on the pedigree.
3. Determine the probability that new baby Addams will have
webbed feet (recessive trait).
The Addams Family Pedigree for Webbed Feet
B = normal feet
b = webbed feet
Grandpa
Addams
Grandma
Addams
Mother
Addams
Cousin It
Father
Addams
Fester
Gomez
Pugsley
Morticia
Wednesday
??????
New Baby
Addams
 What is the probability that new baby Addams will have webbed feet? ________
30
Part B: Creating a Family Pedigree
1. Draw the following pedigree. Albinism (a) is a recessive trait.
John and Sally have a son, J.J. and daughter, Olivia
(youngest) with normal pigmentation. They also have a middle son,
Ethan that is an albino. Another couple, Dave and Judy have one son,
Rob (oldest) and two daughters Beth and Becky with normal
pigmentation.
Olivia from the first couple had three children with Rob of the second couple. Their
son, Scott and one daughter, Abby have albinism. Yet, their youngest daughter, Mary, has
normal pigmentation.
2. Label the generations and label each individual in the pedigree by placing their name BELOW
the shape.
3. Determine the genotypes of all the individuals and write the correct genotype INSIDE the
person’s symbol.
31
Part C: Analyzing a Pedigree
1. Observe the following pedigree for tongue-rolling (T/t). Note: shaded individuals
cannot roll their tongues!
1
I.
II.
1
III.
1
2
2
3
2
4
3
4
5
5
6
6
Answer the following questions:
1.
The ability to roll the tongue into a U-shape is determined by a single gene. Determine if you can roll your
tongue.
yes_______ no_______
2. Do any of the children in generation II have the same phenotype as their father? ______________
3. In which generation do children appear with the same phenotype as individual I-1? _______________
4. Look at the pedigree. Is tongue-rolling a dominant or recessive trait? Explain how you know.
5. Determine each individual’s genotype.
6. What is the relationship between individual I.-2 and III.-4? Be specific. _______________________
7. Individuals II-4 and II-5 have the same phenotype. Three of their children have the same phenotype,
but one, III-6, does not. What genotypes must individuals II-4 and II-5 be to produce children with
these phenotypes? Explain.
8. If individual II-5 married a woman who cannot roll her tongue, what is the probability that they would
have a child that could roll his/her tongue? ____________________
32
REVIEW Packet: Patterns of Heredity
Name ____________________________________Period: ______Date:_____________
Part 1: MATCHING: Choose the best definition for each vocabulary term.
_____1. A diagram that shows how a particular trait
is shown in a family
A. autosomes
_____2. mutation that occurs when a segment of a
chromosome breaks off and is reinserted backwards.
B. aneuploidy
_____3. abnormal number of chromosomes
C. pedigree
_____4. mutation that occurs when one chromosome of
a pair is missing
_____5. More than one gene controlling a trait
D. polyploidy
_____6. Anything that can cause a mutation
F. nondisjunction
_____7. Body chromosomes; pairs 1-22
G. frame shift mutation
_____8. Error in DNA that adds or deletes a single
base that causes all following amino acids
to be affected
H. Gregor Mendel
E. mutagen
I. translocation
_____9. A chart where the chromosomes are arranged in
their homologous pairs
____10. Failure of homologous chromosomes to
separate during meiosis
J. trisomy
K. inversion
L. polygenic inheritance
____11. “Father of Genetics”
M. karyotype
____12. Piece of one chromosome breaks off and joins
another chromosome
N. monosomy
Part 2: FILL-INS: Complete the following with the best word or words. You may use the words more
than once.
Polygenic Inheritance
Sex-linked trait
Sex Chromosomes
Multiple alleles
Codominance
Incomplete Dominance
XX
XY
1. Some genes are located on sex chromosomes. A ____________________________ is a trait
controlled by these genes.
2. Traits controlled by more than TWO ALLELES are said to have ___________________________
3. ___________________________________are chromosomes that determine the sex of an individual.
4. What are a normal male’s sex chromosomes?______________________________
5. What are a normal female’s sex chromosomes? ______________________________
6. What type of inheritance pattern would the heterozygous offspring be a blend of the two homozygous
parents?___________________________________
7. When the phenotypes of hybrid offspring are showing both traits and NO blending occurs, what type
of inheritance pattern would this be?____________________________
8. What type of inheritance pattern would you use a prime (‘) to notate the alternate form of an
allele?________________________________
33
Part 3: COMPLETION: Answer the following questions concisely.
1. How do you notate sex-linked traits?
2. How do you notate codominant traits?
3. What trait is an example of multiple alleles?
4. What would be an internal factor that can influence gene expression? ______________________
5. What are some environmental (external) factors that can influence gene expression?
6. In sex-linked traits, how would a carrier genotype be written? ______________________
7. Why do sex-linked traits occur more often in males than females?
8. Describe how a karyotype is created?
Part 4: MODES OF INHERITANCE: Read the following problems carefully. If need complete a
Punnett square and answer the questions. Be sure to use the correct notation of genotypes.
______1. When roan cattle are mated, 25% of the offspring are red, 50% are roan, and 25% are white.
Upon examination, it can be seen that the coat of a roan cow consists of both red and white hairs. This
trait is one controlled by_____________________.
A. Sex-linked genes
C. Incomplete dominance
B. Multiple alleles
D. Codominance
______2. What type of inheritance is shown when a red-flowering plant is crossed with a whiteflowering plant and only pink-flowering plants are produced?
A. Inbreeding
C. Incomplete dominance
B. Polygenic inheritance
D. Codominance
34
3. A cross between a homozygous red-flowered snapdragon and a homozygous white-flower snapdragon produces
all pink snapdragons.
a. What type of inheritance makes this possible?________________________________
b. How do you know?_______________________________________________________________
c. Complete the Punnett square for a cross between two pink snapdragons. What are the possible genotypes
and phenotypes of the offspring? Be sure to use the correct notation.
Key:
4. A cross between a homozygous black chicken and a homozygous white chicken produces all back-and-white
checkered chickens.
a. What type of inheritance makes this possible?________________________________
b. How do you know?_______________________________________________________________
c. Complete the Punnett square for a cross between a white and checkered chicken. What are the possible
genotypes and phenotypes of the offspring? Be sure to use the correct notation.
Key:
5. Colorblindness is a sex-linked recessive trait (b). If a female carrier marries a colorblind male, what are their
chances of having a colorblind daughter? Be sure to use the correct notation.
6. A person that has type O blood marries a man that is heterozygous for type A blood. What are the possible
phenotypes of their children? Be sure to use the correct notation.
a. What type of inheritance is human blood types an example of?____________________________
7. A person that has type AB blood marries a woman that is homozygous for type B blood. What are the possible
phenotypes of their children? Be sure to use the correct notation.
8. Many genes control skin color. What type of inheritance pattern makes this possible? ________________
35
Part 5: PEDIGREES: Having dimples is dominant (D) to not having dimples (d). The pedigree chart
illustrates the inheritance of not having dimples. Determine the genotypes of the family and use the chart
to answer the questions.
I
.
II
1
3
7
2
4
5
8
6
9
10
11
III
..
1. Place the correct genotype on the lines below each symbol.
2. How many generations are represented?______________________________
3. What is the relationship between individual I-2 and III.-8? Be specific!________________________
4. What is the genotype of individual II.-3? _________________
a. How do you know?
5. What is the genotype of individual III-10? _________________
a. Why?
6. Individual 11 does not have dimples, yet his father has dimples. Explain how this is genetically
possible.
7. If individual 7 marries a woman who does not have dimples, what are their chances of having a child
with dimples?
36
Unit Learning Map (19 days):
Patterns of Heredity
Mrs. Hostetter
Class: Biology B – PA Standard: 3.3.10: Describe how genetic information is inherited and
expressed. Explain the different types of inheritance.
Unit Essential Question(s):
Optional
Instructional Tools:
How can you explain
the different types of
inheritance patterns?
Concept
Concept
Making a Baby Activity
Genetic Disorder Research
project
Karyotype Activity
Pedigree Project
CSI Activity
Concept
Concept
Incomplete dominance
& Codominance
Multiple Alleles &
Sex-linked crosses
Mutations & Genetic
disorders
Tools: Karyotypes &
Pedigrees
Lesson Essential Questions:
Lesson Essential Questions:
Lesson Essential Questions:
Lesson Essential Questions:
What is the difference
between incomplete
dominance and
codominance crosses?
What is the difference
between multiple
alleles and sex-linked
crosses?
How can a mutation
affect the production of
a protein?
How are karyotypes
and pedigrees used to
help scientists identify
genetic traits?
Vocabulary:
Incomplete dominance
Codominance
Vocabulary:
Multiple alleles
Polygenic inheritance
Sex-linked crosses
Sex Chromosomes
Autosomes
Vocabulary:
Mutation
Mutagen
Nondisjunction
Aneuploidy
Trisomy
Monosomy
Deletion
Insertion
Inversion
Translocation
Point mutation
Frameshift mutation
Vocabulary:
Karyotype
Down Syndrome
Turner Syndrome
Klinefelter Syndrome
Jacob’s Syndrome
Pedigree
Carrier
37
Patterns of Heredity Vocabulary:
1) Incomplete dominance = neither allele for a gene dominates
 Notation:
 Alleles are all capital letters because NEITHER one dominates the other. So one of the
alleles has a prime ( ‘ ) on it to represent an alternate expression of the gene.
2) Codominance = both alleles are expressed equally
 Notation:
 2 different alleles (capital letters) are used
3) Multiple alleles = more than 2 alleles for a single gene can control a trait; example = blood
types
4) Polygenic inheritance = traits are determined by many genes
5) Sex-linked crosses = traits are carried on the sex chromosomes
 Notation:
 The alleles for these traits are written as superscripts on the X chromosome ONLY.
 No alleles are written on the Y chromosome!
 Ex: Colorblind male = XbY and Normal male = XBY
6) Sex chromosomes = last pair of chromosomes—23rd pair for humans; XX = female; XY = male
7) Autosomal chromosome or Autosomes = chromosomes pairs 1-22 for humans
8) Mutation = a random error or change in the DNA sequence that may affect whole chromosomes or
just one gene
9) Mutagen = certain substances or conditions that can create a greater rate of mutation
10) Nondisjunction = failure of homologous chromosomes to separate during meiosis resulting in
gametes (egg or sperm) with too few or too many chromosomes
11) Aneuploidy = abnormal number of chromosomes. Ex: trisomy, monosomy
12) Trisomy = zygote contains three copies of the chromosome
13) Monosomy = zygote contains only one chromosome of the pair i.e. it is missing one chromosome
14) Deletion = occurs when part of a chromosomes is missing.
15) Insertion = occurs when a part of a chromatid breaks off and attaches to its sister chromatid. The
result is a duplication of genes on the same chromosome
16) Inversion = Segment of chromosome breaks off and is reinserted backwards (will flip upside down)
17) Translocation =occurs when part of one chromosomes breaks off and is added to a different
chromosome
18) Point mutation = a change in a single base pair in DNA
19) Frameshift mutation = error in the DNA sequence that adds or deletes a single nitrogen base,
causing nearly all amino acids following the mutation to be changed
20) Karyotype = a test to identify and evaluate the size, shape, and number of chromosomes in a sample
of body cells
38
21) Down syndrome = also known as trisomy 21
 Cause = nondisjunction of the 21st pair of chromosomes
 Characteristics:
 Happens equally in males and females since it does notinvolve the sex chromosomes
 Individuals are mentally handicapped but the severity varies with the individual
 The probability of giving birth to a child with Down syndrome increases with age of the
mother, increasing significantly after age 35
22) Turner syndrome =
 Cause = nondisjunction of the sex chromosomes during meiosis so individuals are missing one
copy of the X chromosome.
 They have 22 pairs of autosomal chromosomes and only one X chromosome.
 Characteristics:
 Affects ONLY females. 4
 Women are usually short, sexually underdeveloped and sterile.
 Women with this syndrome function well within society and are not diagnosed until they are
assessed for infertility as adults.
23) Klinefelter syndrome = (XXY)
 Cause = nondisjunction of the sex chromosomes during meiosis so individuals have an extra X
chromosome
 The person has 22 autosomal chromosomes and 3 sex chromosomes (XXY).
 Characteristics:
 Affects ONLY males.
 Males are often tall, sexually underdeveloped and may have slight intellectual impairment.
 Recognition of this syndrome before puberty usually does not occur.
 Many males with this syndrome function well within society and are not diagnosed until they
are assessed for infertility as adults.
24) Jacob's syndrome = XYY
 Cause = occurs when a male inherits two Y chromosomes from his father instead of one. The exact
cause of why this occurs is unknown.
 Individuals with Jacob’s syndrome have 22 autosomal chromosomes and 3 sex
chromosomes (XYY).
 He is an XYY male. Remember most males are XY.
 Characteristics:
 Affects ONLY males.
 The most common symptoms are learning problems at school and delayed emotional
maturity.
 Males are tall, thin, have acne, speech problems, and reading problems
25) Pedigrees = a valuable tool for anyone working in the field of genetics
26) Carrier = Heterozygous FEMALES; XBXb
39