Intro to Genetics
Chapter 11.1-11.3
p. 306-322
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Key
terms
• Genetics
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Fertilization
Trait
Hybrid
Gene
Allele
Principle of dominance
Segregation
Gamete
Probability
Homozygous
Heterozygous
Phenotype
Genotype
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Punnett square
Independent assortment
Incomplete dominance
Codominance
Multiple allele
Polygenic trait
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Review?
Heredity: What is a gene?
is a segment of DNA that is located in a
chromosome and that codes for a
specific trait
Crossing over: How does it contribute to
the physical differences between
siblings?
exchange of genetic material between
homologous chromosomes genetic
recombination
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THINK ABOUT IT
What is an inheritance?
It is something we each receive from our parents—a contribution that
determines our blood type, the color of our hair, and so much more.
What kind of inheritance makes a person’s face round or hair curly
Where does an organism get its unique characteristics
 An individual’s characteristics are determined by factors that are
passed from one parental generation to the next.
 The delivery of characteristics from parent to offspring is called
heredity.
 The scientific study of heredity, known as genetics, is the key to
understanding what makes each organism unique
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leucism
• This alligator is one of 18 white alligators discovered
southwest of New Orleans in 1987 by a fisherman.
• How is he different from alligators you have seen?
• It is not a different species and it is not albino.
• Albinos have off-white or yellowish skin and colorless
irises or look pink
• This alligator is more rare than one that would be an
albino.
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Need to know!!
1. Describe how Mendel was able to control his
pea plants were pollinated.
2. Describe the steps in Mendel's experiments on
true-breeding garden peas.
3. Distinguish between dominant and recessive
traits.
4. State two laws of heredity that were developed
from Mendel’s work
5. Describe how Mendel's results can be
explained by scientific knowledge of genes and
chromosomes
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Mendel’s Legacy
• Genetics is the field of biology devoted to
understanding how characteristics or traits
are transmitted from parents to offspring.
Genetics was founded with the work of
Gregor Johann Mendel.
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Gregor Mendel1822-1884
• Studied science and mathematics (statistics)
• Studied heredity (characteristics from parents to
offspring)
• Studied garden peas, characteristics, flower
color, height, pod appearance, texture or traits
• A trait is a specific characteristic of an individual,
such as seed color or plant height, and may vary
from one individual to another.
Led to basic principles of genetics
•
•
Web demo holt
http://my.hrw.com/index.jsp
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Mendel’s Methods
•
•
Controlled how plants were pollinated
Or how the pollen grains produced in the
male reproductive parts of a flower
(anthers/stamen) to the female
reproductive parts of the flower
(stigma/pistle)
Two types:
1. Self- pollination
2. Cross pollination
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Mendel’s Methods cont:
1. Self- pollination- occurs when pollen is
transferred from the anthers of a flower to the
stigma of either that flower or another flower
on the same plant.
*Can be prevented if remove male parts
2. Cross-pollination- occurs between flowers of
two plants, can be specific for traits
*Mendel used this method to study plants
Web demo holt
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control breeding
• Self- fertilize- sperm-carrying pollen grains
released from the stamens land on the eggcontaining carpel of the same flower
• Cross-fertilization- fertilization of one plant by
pollen from a different plant
(cut off the immature stamens)
• True-breeding- offspring identical to parent
• Hybrids- has two different varieties
• P, F1, and F2 generation
• Go to: http://my.hrw.com/ (lbell06)
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Patterns of Inheritance
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Mendel’s Experiments
• True-breeding or pure for a trait will produce offspring
with a trait of self-pollinate
Ex: yellow pod x yellow pod = yellow pod
• Cross pollinated pairs of plants that were true-breeding
for one trait and then another
• True-breeding parents were P generation
• First generations F1
• Second generations F2
• Mendel’s crosses
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Fig. 14-3-1
EXPERIMENT
P Generation
(true-breeding
parents)
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Patterns of Inheritance

Purple
flowers
White
flowers
16
Fig. 14-3-2
EXPERIMENT
P Generation
(true-breeding
parents)
F1 Generation
(hybrids)
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Patterns of Inheritance

Purple
flowers
White
flowers
All plants had
purple flowers
17
Fig. 14-3-3
EXPERIMENT
P Generation
(true-breeding
parents)
F1 Generation
(hybrids)

Purple
flowers
White
flowers
All plants had
purple flowers
F2 Generation
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Patterns of Inheritance
705 purple-flowered 224 white-flowered
plants
plants
18
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Genes and Alleles
From these results, Mendel drew two conclusions. His first conclusion
formed the basis of our current understanding of inheritance.
An individual’s characteristics are determined by factors that are passed
from one parental generation to the next.
Scientists call the factors that are passed from parent to offspring genes.
Each of the traits Mendel studied was controlled by one gene that occurred
in two contrasting varieties.
These gene variations produced different expressions, or forms, of each
trait.
The different forms of a gene are called alleles
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Dominant and Recessive Traits
Mendel’s second conclusion is called the principle of dominance. This
principle states that some alleles are dominant and others are recessive.
An organism with at least one dominant allele for a particular form of a trait
will exhibit that form of the trait.
An organism with a recessive allele for a particular form of a trait will exhibit
that form only when the dominant allele for the trait is not present.
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Segregation
How are different forms of a gene
distributed to offspring?
During gamete formation, the
alleles for each gene segregate
from each other, so that each
gamete carries only one allele for
each gene.
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Results and conclusions
• Pair of factors (genes) controlled for traits
• Only one trait was visible in F1 generation
(dominant factor)
• Traits appeared in the F2 generations in
3:1 ratio (recessive factor)
• Law of segregation- pair of factors are
separated during formation of gametes or
meiosis
• Law of Independent Assortment- factors
separate independently of one another
during the formation of gametes (meiosis)
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Lesson Overview
11.2 Applying Mendel’s
Principles
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Key questions?
• Differentiate between the genotype and the phenotype
of an organism
• Explain how probability is used to predict the results of
genetic crosses
• Use a Punnett square to predict the results of a
monohybrid and dihybrid genetic crosses
• Explain how a testcross is used to show the genotype of
an individual whose phenotype expresses the dominant
trait
• Differentiate a monohybrid cross from a dihybrid cross
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Chromosomes and Inheritance
• Francis Collins and his lab group discovered
the gene responsible for Cystic Fibrosis. CS is
often fatal genetic disorder. Thick, sticky
mucus builds up and blocks ducts in the
pancreas and intestines and causes difficulty
in breathing.
• In this chapter we will learn how diseases and
characteristics are inherited and expressed.
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Genetic Crosses
• Today, geneticists rely on Mendel’s work
to predict the likely outcome of genetic
crosses. In this section you will learn how
to predict the probable genetic makeup
and appearance of offspring resulting from
specified crosses.
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Probability and Punnett Squares
How can we use probability to predict traits?
Punnett squares use mathematical probability to help predict the genotype
and phenotype combinations in genetic crosses.
Mendel realized that the principles of probability could be used to explain
the results of his genetic crosses.
Probability is the likelihood that a particular event will occur.
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Probability and Punnett Squares
For example, there are two possible outcomes of a coin flip: The coin
may land either heads up or tails up.
The chance, or probability, of either outcome is equal. Therefore, the
probability that a single coin flip will land heads up is 1 chance in 2. This
amounts to 1/2, or 50 percent
If you flip a coin three times in a row, what is the probability that it will land
heads up every time?
Each coin flip is an independent event, with a one chance in two
probability of landing heads up.
Therefore, the probability of flipping three heads in a row is:
1/2 × 1/2 × 1/2 = 1/8
Past outcomes do not affect future ones. Just because you’ve flipped
3 heads in a row does not mean that you’re more likely to have a
coin land tails up on the next flip
.
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Probability
• The likelihood that a specific event will
occur.
• Can be expressed as a:
– Decimal
– Percentage
– Fraction
Probability=(# of time event expected to
happen)/ (# of time it could happen)
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Using Segregation to Predict Outcomes
The way in which alleles
segregate during gamete
formation is every bit as random
as a coin flip.
Therefore, the principles of
probability can be used to
predict the outcomes of genetic
crosses.
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Terms
1. Genotype- genetic makeup, alleles that
are inherited from parents (PP, Pp, pp)
2. Phenotype- physical appearance (color,
height), does not always resemble
genotype due to environment factors
3. Homozygous- alleles are the same, can
be dominant (PP) or recessive (pp)
4. Heterozygous- alleles are different (Pp)
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More terms
1. Monohybrid cross- cross with only one
characteristic, offspring are monohybrids
2. Punnett square- used to do monohybrid
crosses, used to predict outcomes
3. Genotypic ratio- ratio of genotypes that
appear (1BB: 2Bb: 1bb)
4. Phenotypic ratio- ratio of phenotypes
that appear (3 brown : 1 black)
5. Test cross- unknown organism is
crosses with a homozygous recessive
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Test Cross
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Patterns of Inheritance
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How To Make a Punnett Square for a OneFactor Cross
Write the genotypes of the two organisms that will serve as parents in a
cross.
In this example we will cross a male and female osprey that are
heterozygous for large beaks. They each have genotypes of Bb.
Bb and Bb
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How To Make a Punnett Square
Draw a table with enough spaces for each pair of gametes from each
parent.
Enter the genotypes of the gametes produced by both parents on the
top and left sides of the table.
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How To Make a Punnett Square
Fill in the table by combining the gametes’ genotypes.
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How To Make a Punnett Square
Determine the genotypes and phenotypes of each offspring.
Calculate the percentage of each. In this example, three fourths of the
chicks will have large beaks, but only one in two will be heterozygous.
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Types of crosses:
A. Homozygous x Homozygous (PP x pp)
B. Homozygous x Heterozygous (PP x Pp)
(complete dominance)
C. Heterozygous x Heterozygous (Pp x Pp)
D. Test cross (pp x P_)
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Types of crosses:
E. Incomplete
dominance- F1
offspring has a
phenotype in
between that of
parents, Cross a
white (rr) flower with
a Red flower (RR)=
pink flower (Rr)
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Types of crosses
F. Codominance-both
alleles fro a gene
are expressed on a
heterozygous
offspring, neither
trait is dominant or
recessive, blood
types
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Blood Types - Multiple Alleles and
Codominance
• In humans, there are four blood types
(phenotypes): A, B, AB, and O
• Blood type is controlled by three alleles. A, B, O
• O is recessive, two O alleles must be present for
the person to have type O blood
• A and B are codominant. If a person receives an
A allele and a B allele, their blood type is type
AB
• Crosses involving blood type often use an I to
denote the alleles - see chart.
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Blood types
• The blood type determines what antibodies are
located within the blood. Type A blood has type
B antibodies. If type B blood is put into their
bodies, their immune system reacts as if it were
a foreign invader, the antibodies clump the blood
- can cause death.
• Type AB blood has no antibodies, any blood can
be donated to them - they are called the
"universal acceptors"
• Type O blood has no surface markers on it,
antibodies in the blood do not react to type O
blood, they are called the "universal donors"
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Multiple alleles
• Having more than 3 alleles
• Blood type ABO, codominance (fig 12.12)
–
–
–
–
A
B
AB
O
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Fig. 14-11
Allele
IA
IB
Carbohydrate
A
B
i
none
(a) The three alleles for the ABO blood groups
and their associated carbohydrates
Genotype
Red blood cell
appearance
Phenotype
(blood group)
IAIA or IA i
A
IBIB or IB i
B
IAIB
AB
ii
O
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Blood group genotypes and phenotypes
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Codominant and Multiple Alleles
This table shows the relationship between genotype and phenotype for the
ABO blood group.
It also shows which blood types can safely be transfused into people with
other blood types.
Alleles IA and IB are codominant. They produce molecules known as
antigens on the surface of red blood cells.
Individuals with alleles IA and IB produce both A and B antigens, making
them blood type AB.
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More genetic traits
Incomplete dominance- trait hair, and curly
hair parents have a wavy hair child
X- linked- carried on the x chromosomes,
color blindness is a recessive x linked
Sex-influenced traits- dependent on male
or female, baldness, have same genotype,
tend to be autosomal, hormones play role
Single-allele traits- 200 dominate alleles,
Huntington's (HD)autosomal, pass genes
before they are aware have it (30-40ys)
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A little Q and A
Can you ID some parts to the
chromosomes
- centromere, chromatids
How many chromosomes are found in the
normal human genome
46 (2n)
Each chromosome contains many genes
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A little Q and A
Differences between dominant and
recessive
dominance: when an allele that masks
the presence of another allele for the
same characteristic
Recessive: when an allele that is masked
by the presence of another allele for that
same characteristic
Can you give examples?
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Objectives
• Distinguish between sex chromosomes
and autosomes
• Explain the role of sex chromosomes in
sex determination
• Describe how an X or Y linked gene
affects the inheritance of genes in linkage
groups
• Distinguish between chromosomes
mutations and gene mutations
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Chromosomes
• 1900s Thomas Hunt Morgan
experimented with Drosophila
melanogaster
• Observed that they had 4pairs of
chromosomes
• 3 pairs were identical in male and female
• The fourth pairs was the sex
chromosomes XX female, XY male
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Sex chromosomes and
autosomes
• Sex chromosomes- contain genes that
determine the sex (gender) of an individual
• Autosomes- non sex chromosomes
Sex determinationSex chromosomes pair during meiosis
Child will always receive a x chromosome from the
mother
SRY gene- sex-determining Region Y, if have this
gene hormones are released and testes form
and if not ovaries form
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What is the difference between an
Autosome and a Sex-chromosome?
• Autosomes are the first
22 homologous pairs of
human chromosomes
that do not influence
the sex of an individual.
• Sex Chromosomes are
the 23rd pair of
chromosomes that
determine the sex of an
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Can you determine the probability
of the sex of the child?
1. Cross a Male and a Female
XY x XX
2. Set up your punnett square
3. What are your ratios?
4. Who determines the sex of the child?
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Sex Chromosomes
This Punnett square illustrates
why males and females are
born in a roughly 50 : 50 ratio.
All human egg cells carry a
single X chromosome (23,X).
However, half of all sperm
cells carry an X chromosome
(23,X) and half carry a Y
chromosome (23,Y).
This ensures that just about
half the zygotes will be males
and half will be females.
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Sex Chromosomes
More than 1200 genes are found
on the X chromosome, some of
which are shown.
The human Y chromosome is
much smaller than the X
chromosome and contains only
about 140 genes, most of which
are associated with male sex
determination and sperm
development.
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Effects of Gene location
• Sex-linked genes and traits
some genes are located on the sex chromosomes
Ex: in DM the gene for eye color is located on the X
chromosome, Y chromosome lacks this gene
Do this cross:
1. (p1) cross an X(R ) X(R ) female red eye with an X(r )
Y male white eye, what is the F1 generation?
Now take two from the F1 and cross them and see what
you get?
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Sex- linked genes and traits
• The results of these experiments showed
Morgan not only genes reside on
chromosomes but that red eye color is
located on the X chromosome
• Genes can be both x linked or y linked
• Sex linked trait –is coded for by an allele
on a sex chromosome
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Sex-Linked Traits:
•Some genes are found on the sex
chromosomes
•Some are found on the X sex chrom. but not
the Y
Ex – the color vision gene is on the X
chromosome
- NOT FOUND ON THE “Y”
Sex-linked traits are RECESSIVE (mostly) traits
that are found on the ‘x’ sex chromosome
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Can you see the hidden numbers?
Color blindness Self Test:
NUMBERS: 5 | 8 | 9 | 5 | 3 | 5 | 9 | 10 |
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•Red-green colorblindness is a recessive sex-linked trait, found on the X
chromosome, not the Y.
•Males only have one X chromosome, they have a much greater chance of
having red-green colorblindness.
•Females would have to be homozygous recessive in order to have red-green
colorblindness.
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Hypertrichosis –
Human Werewolf Syndrome:
Congenital generalized hypertrichosis (CGH)
Rare, X-linked dominant trait
Found in a single multigenerational Mexican
family
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Why do males go bald???
•Females have 2 X chromosomes so they
can be “carriers” for the sex-linked trait but
their phenotype is the normal condition
•One of the chromosomes can “mask” the
sex-linked trait
•Males have only 1X chromosome so if they
get the recessive trait that is a sex-linked
trait, then they will show it.
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Practice problems:
• Try this quiz on Sex-linked genes
http://www.ksu.edu/biology/pob/genetics/xlinked.htm
• Complete the problem set on sex-linked
traits
http://www.biology.arizona.edu/mendelian_genetics/problem
_sets/sex_linked_inheritance/sex_linked_inheritance.html
• Write your answers out… include the
punnett squares that are necessary to
figure the answer out!
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More practice:
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Another one….
• A man with normal vision marries a
woman who is a carrier for color
blindness. What are the possible
genotypes and phenotypes of their
children.
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Linked Genes
• Pairs of genes that tend to be inherited
together
• Genes are linked because they are found
on the same chromosome
• Crossing over during meiosis does not
create new genes or delete old ones, just
rearranges alleles
• Linkage group- set of linked genes
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Chromosome mapping
• The farther apart the genes are located on
a chromosome, increases the chance of
cross-over
• Chromosome map- diagram that shows
the linear order of genes on a
chromosome
• Map unit- frequency of crossing-over
• Today modern technology has made it
easier to map genes (human genome
project)
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Independent Assortment
How do alleles segregate when more than one gene is involved?
The principle of independent assortment states that genes for
different traits can segregate independently during the formation of
gametes.
Mendel wondered if the segregation of one pair of alleles affects another pair.
Mendel performed an experiment that followed two different genes as they
passed from one generation to the next.
Because it involves two different genes, Mendel’s experiment is known as
a two-factor, or dihybrid, cross. Single-gene crosses are monohybrid
crosses.
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Dihybrid crosses
•
Two characteristics are tracked, results
are dihybrid
Types of crosses( 4 x4 box)
1. Homozygous RRYY x Homozygous rryy
2. Heterozygous RrYy x Heterozygous
RrYy (9:3:3:1)
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Fig. 14-8
EXPERIMENT
YYRR
P Generation
yyrr
Gametes YR

F1 Generation
YyRr
Hypothesis of
dependent
assortment
Predictions
yr
Hypothesis of
independent
assortment
Sperm
or
Predicted
offspring of
F2 generation
1/
4
Sperm
1/ YR 1/
2
2 yr
1/
4
1/
2
YR
1/
4
1/
4
Yr
yR
1/
4
yr
YR
YYRR YYRr
YyRR
YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR
YyRr
yyRR
yyRr
YyRr
Yyrr
yyRr
yyrr
YR
YYRR
Eggs
1/
2
YyRr
1/
4
Yr
Eggs
yr
YyRr
3/
4
yyrr
1/
4
yR
1/
4
Phenotypic ratio 3:1
1/
4
yr
9/
16
3/
16
3/
16
1/
16
Phenotypic ratio 9:3:3:1
RESULTS
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Patterns of Inheritance
108
101
32
Phenotypic ratio approximately 9:3:3:1
82
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Fig. 14-12
BbCc

BbCc
Sperm
1/
4 BC
1/
4 bC
1/
4 Bc
1/
4 bc
Eggs
1/
1/
1/
1/
4 BC
BBCC
BbCC
BBCc
BbCc
BbCC
bbCC
BbCc
bbCc
BBCc
BbCc
BBcc
Bbcc
BbCc
bbCc
Bbcc
bbcc
4 bC
4 Bc
4 bc
9
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Patterns of Inheritance
: 3
: 4
84
Labrador Retriever Genetics
• Black is dominant to chocolate B or b
Yellow is recessive epistatic (when present, it blocks the
expression of the black and chocolate alleles) E or e
Black
BBEE
BbEE
BBEe
BbEe
Chocolate bbEE
bbEe
Yellow
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BBee
Bbee
bbee
85
Task: Determine the number of chocolate
labs produced from a black female and a
yellow male (BbEe x bbee)
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A Summary of Mendel’s Principles
What did Mendel contribute to our understanding of
genetics?
Mendel’s principles of heredity, observed through patterns of
inheritance, form the basis of modern genetics
At the beginning of the 1900s, American geneticist Thomas Hunt
Morgan decided to use the common fruit fly as a model
organism in his genetics experiments.
The fruit fly was an ideal organism for genetics because it could
produce plenty of offspring, and it did so quickly in the laboratory.
Before long, Morgan and other biologists had tested every one of
Mendel’s principles and learned that they applied not just to pea
plants but to other organisms as well.
The basic principles of Mendelian genetics can be used to study the
inheritance of human traits and to calculate the probability of certain
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traits appearing in theChapter
next 11
generation.
objectives
• Analyze pedigrees to determine how genetic
traits and genetic disorders are inherited
• Summarize the different patterns of inheritance
seen in genetic traits and genetic disorders
• Explain the inheritance of ABO blood groups
• Compare sex-linked traits with sex-influenced
traits
• Explain how geneticists can detect and treat
genetic disorders
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Human Genetics
• This section investigates how genetics
analyze genetic data from families to track
the inheritance of human genes. It also
explores the genetic and environmental
factors that influence human genetic traits
and disorders, and discusses how
geneticists detect and treat human genetic
disorders.
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Inheritance of traits
Why do geneticists study human genetic traits?
To trace genetic diseases from generation to
generation
Study the phenotypes of family members in
a pedigree
Pedigrees- diagram that shows how a trait is
inherited over several generations
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Patterns of inheritance-
Expression of genes over generations
• Autosomal traits- appear in both sexes equally
• Sex-linked- tend to see only in males, most are
recessive
• Carriers- they have one copy of the allele but do
not have the disease, they do not express the
disease but can pass it to offspring
-Most are born from normal parents
(phenotypically normal) who carries the
recessive gene (allele)
-Inbreeding- increases the chances of expression
of recessive traits
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This will be on OGT
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Fig. 14-15b
1st generation
(grandparents)
2nd generation
(parents, aunts,
and uncles)
Ww
ww
ww
Ww ww ww Ww
Ww
Ww
ww
3rd generation
(two sisters)
WW
or
Ww
Widow’s peak
ww
No widow’s peak
(a) Is a widow’s peak a dominant or recessive trait?
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94
Fig. 14-15c
1st generation
(grandparents)
Ff
2nd generation
(parents, aunts,
and uncles)
FF or Ff ff
Ff
ff
ff
Ff
Ff
Ff
ff
ff
FF
or
Ff
3rd generation
(two sisters)
Attached earlobe
Honors:Chapter
(b) Is an9 attached
Patterns of Inheritance
Free earlobe
earlobe a dominant or recessive trait?
95
Honors:Chapter 9
Patterns of Inheritance
96
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inherited disorders
Dominant Disorders- only need one trait
1. achondroplasis- dwarfism
2. Huntington’s – mental deterioration,
middle ages
Less likely to be passes if deadly – don’t
reproduce
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Fig. 14-16
Parents
Normal
Aa

Normal
Aa
Sperm
A
a
A
AA
Normal
Aa
Normal
(carrier)
a
Aa
Normal
(carrier)
aa
Albino
Eggs
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Fig. 14-17
Parents
Dwarf
Dd

Normal
dd
Sperm
D
d
d
Dd
Dwarf
dd
Normal
d
Dd
Dwarf
dd
Eggs
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Patterns of Inheritance
Normal
100
Genetic traits and disorders
• Genetic disorders are diseases that have
genetic origin
• Polygenic inheritance- characteristics
are influenced by many genes
– Skin color (3-6 genes), eye color, height
 Complex characters-influenced strongly
both by the environment and by genes
 Skin color is both polygenic and complex,
cancers
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single gene may affect many phenotypic
characteristics
• Pleiotropy- genes influence multiple
characteristics
example
• Fig 9.14 sickle-cell, 1 thing  chain events
• coloration pattern and crossed eyes of Siamese
cats, which are both caused by the same allele.
These unrelated characters are caused by the
same protein produced by the same allele.
• gene that causes pigment color in rats. White
rats also have very sensitive eyes and often
become blind.
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Detecting Genetic Disease
• If you have family history see testing
• Genetic screening- Karyotype, blood
tests,
• Detect 200 disorders in the fetus by
amniocentesis
• Chorionic villi sampling- take cells from
zygote between the mothers uterus and
placenta between 8-10wks
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Fig. 14-18
Amniotic fluid
withdrawn
Centrifugation
Fetus
Fetus
Placenta
Uterus
Placenta
Cervix
Fluid
Fetal
cells
BioSeveral chemical
hours
tests
Several
weeks
Several
weeks
(a) Amniocentesis
Honors:Chapter 9
Patterns of Inheritance
Karyotyping
Chorionic
villi
Several
hours
Suction tube
inserted
through
cervix
Fetal
cells
Several
hours
(b) Chorionic villus sampling (CVS)
105
Karyotype
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Questions about a Karyotype?
1. What term do we use to describe the pair
of chromosomes?
2. How are the chromosomes that make up
each number pair similar?
3. What chromosomes are autosomes?
4. Which are sex chromosomes?
5. Can you explain any abnormalities?
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Abnormal number of sex
chromosomes
• XXY Klinefelter - male sex organs, testes
small, individual is sterile, breast enlargement,
other female characteristics, normal intelligence
(meiosis in egg/sperm)
• XYY normal male- can be taller, (meiosis in
sperm)
• XXX normal female –(meiosis egg/ sperm)
• XO Turner syndrome (female, egg/sperm),
sterile, short stature, artificial estrogen
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Genetic Counseling
• Process of informing a person about the
parents or potential new Childs genetic
makeup
• Problems that could affect the offspring
• Predict the probability that offspring will be
healthy or have a genetic disorder
• Risk factors
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Treating genetic diseases
• PKU- lacks the enzyme, causes mental
retardation, strict foods, no diet soda,
blood tests
• CF- pounding on the back 45min sessions
Gene therapy- replacing the defective gene
Somatic cell gene therapy
Germ cell gene therapy- eggs and sperm
Is this ethical- how does this affect the next
generation???
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Environment play a role
• Combination of heredity and environment
List some examples
1. mother nature, wind, sun,
2. nutrition, exercise, sun
3. nature vs nurture
genetic testing- can detect disease-causing
alleles
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What We Have Learned
In June 2000 scientists announced that a working copy of the
human genome was complete.
The first details appeared in the February 2001 issues of the
journals Nature and Science.
The full reference sequence was completed in April 2003, marking
the end of the Human Genome Project—two years ahead of
the original schedule.
The Human Genome Project found that the human genome in its
haploid form contains 3 billion nucleotide bases.
Only about 2 percent of our genome encodes instructions for
the synthesis of proteins, and many chromosomes contain
large areas with very few genes.
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What We Have Learned
As much as half of our genome is made up of DNA sequences from
viruses and other genetic elements within human chromosomes.
More than 40% of our proteins are similar to proteins in organisms such as
fruit flies, worms, and yeast.
This chart compares the human genome with other organisms.
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What We Have Learned
The Human Genome Project pinpointed genes and associated particular
sequences in those genes with numerous diseases and disorders.
It also identified about three million locations where single-base DNA
differences occur in humans, which may help us find DNA sequences
associated with diabetes, cancer, and other health problems.
The Human Genome Project also transferred important new technologies to
the private sector, including agriculture and medicine.
The project catalyzed the U.S. biotechnology industry and fostered the
development of new medical applications.
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New Questions
The Human Genome Project worked to identify and address ethical, legal,
and social issues surrounding the availability of human genome data and its
powerful new technologies.
For example, who owns and controls genetic information? Is genetic privacy
different from medical privacy? Who should have access to personal genetic
information, and how will it be used?
In May 2008, President George W. Bush signed into law the Genetic
Information Nondiscrimination Act, which prohibits U.S. insurance
companies and employers from discriminating on the basis of information
derived from genetic tests. Other protective laws may soon follow.
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What’s Next?
The 1000 Genomes Project, launched in 2008, will study the genomes of 1000 people
in an effort to produce a detailed catalogue of human variation.
Data from the project will be used in future studies of development and disease, and
may lead to successful research on new drugs and therapies to save human lives and
preserve health.
In addition, many more sequencing projects are under way and an ever-growing
database of information from microbial, animal, and plant genomes is expected.
Perhaps the most important challenge that lies ahead is to understand how all the
“parts” of cells—genes, proteins, and many other molecules—work together to create
complex living organisms.
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Fig. 14-UN2
Degree of dominance
Complete dominance
of one allele
Example
Description
Heterozygous phenotype
PP
same as that of homozygous dominant
Pp
Incomplete dominance Heterozygous phenotype
intermediate between
of either allele
the two homozygous
phenotypes
C RC R
Codominance
Heterozygotes: Both
phenotypes expressed
C RC W C WC W
IAIB
Multiple alleles
In the whole population, ABO blood group alleles
some genes have more
IA , IB , i
than two alleles
Pleiotropy
One gene is able to
affect multiple
phenotypic characters
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Sickle-cell disease
118
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119
Pop quiz- terms
1. Genetics- study of heredity (traits past from parent to offspring)
2.
Genotype- genetic makeup, alleles that are inherited from parents (PP,
Pp, pp)
3.
Phenotype- physical appearance (color, height), does not always
resemble genotype due to environment factors
4.
Heterozygous- alleles are different (Pp)
5.
Homozygous- alleles are the same, can be dominant (PP) or recessive
(pp)
6.
Test cross- used to identify the unknown genotype of an organism that is
expressing the dominant phenotype, cross it with a homozygous
recessive individual
7.
Dominant- An organism with at least one dominant allele for a particular
form of a trait will exhibit that form of the trait.
8.
Recessive - An organism with a recessive allele for a particular form of a
trait will exhibit that form only when the dominant allele for the trait is not
present.
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