Chapter 10 - Genetics
Genetics is the study of
H
is the passing of traits from parent to offspring
Study of Genetics


Children inherit traits
Need to study many
a section of DNA on chromosomes

Paired
 1 from mom
& 1 from dad
Gregor Mendel (1857) “Father of Genetics”

Discovered patterns of
by breeding pea plants
Mendel’s Experiments


Used pea plants because they are Easy to
& can be
Hypothesized that “
” carry information about traits
Flower Anatomy


Certain varietes of garden pea plants
generation after generation.
Mendel performed
gametes) from one true-breeding plant to the
breeding plant.
specific forms of a
by transferring
(male
(female organ) of another true-
Cross Pollination



Mendel
Prevented self-pollination!
Trait: Yellow vs. Green
the
(male organ) of the pea plant!
Mendel Studied 7 Traits:
Mendel Concluded:
1

Must be
forms of a trait which is controlled by a
.
, known now as an
What We Know Now



“Factors” are called genes
Different forms of a gene are called
Represented by letters
Ex. flower color alleles
P (purple) or p (white)
Alleles
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

= dominant allele
Ex. P (purple)
= recessive allele
Ex. p (white)
= alleles (letters) that make up that trait
Ex. PP

= physical appearance of trait



Ex. Purple

Ex. PP or pp

two of the same alleles (a.k.a. purebreed)
two different alleles (a.k.a. hybrid)
Ex. Pp
Mendel’s Laws

Alleles separate when gametes are formed

traits are not inherited together
Inheritance Of Traits

If you inherit one
the recessive allele will not be
Predicting Our Traits


squares show possible genotypes



100 % Heterozygous
Their genotype is Gg
Their phenotype is green
Monohybrid Cross:


Punnett Squares that analyze only
Depending on the parents alleles they can produce
for that trait.
2
Dihybrid Cross:



Punnett Squares that analyze
If both parents are homozygous for the two traits only one gamete can be formed (
).
If parents are heterozygous for the two traits than
of alleles from male gametes and
of alleles from female gametes can be formed.

Phenotypic Ratio is:
9:3:3:1
Genotypes: almost all
different!
Probability




Measure of
something will occur
Ex. What is the probability of getting heads
when you flip a coin?
Punnett squares used to predict the probability of
!
Actual data not perfectmore likely match the results predicted.
Recessive Genetic Disorders

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
Need to inherit
Tay Sachs
Sickle Cell Anemia
Cystic Fibrosis
Albinism
Galactosemia
copies of recessive allele
Dominant Genetic Disorders

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
Only need
Polydactyly
Marfan Syndrome
Huntington’s Disease
Achondroplasia
of dominant allele
Ch 11.2 Complex Patterns of Inheritance

Most
are not simply dominant or recessive
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Incomplete Dominance

Dominant & recessive traits appear to "
"
Ex. snapdragon flowers
red x white = pink
RR
X
rr
= Rr
Incomplete Dominance

A homozygous dominant black cat is crossed with a gray cat and black is incompletely dominant over
white. What is the percentage of having a gray kitten?
Incomplete Dominance

A gray cat is crossed with another gray cat and black is incompletely dominant over white. Complete a
Punnett square and tell me what is the genotypic and phenotypic ratio of that cross?
Codominance

traits are both fully seen
“Co”=
Ex. Roan Horses have both red & white hairs
Codominance

Both alleles should be
another.
since one is not dominant over
Codominance

In humans, wavy hair (CS) results by the co-dominance pattern of curly hair (C) and straight hair (S).
What are the possible results if a wavy-haired man and a straight-haired woman have children?
List Genotypic and Phenotypic Ratios!
Multiple Alleles

or

control the
Ex. Human ABO blood groups
4
Multiple Alleles

A woman with type B (heterozygous) blood and a man
with type AB blood are expecting a child. What are the
possible blood types of the kids?
Multiple Alleles

A test was done to determine the biological father of a child. The child’s blood Type is B and the
mother’s is Type A. Dude #1 has blood type O and dude # 2 has blood type AB. Which dude is the
biological father?
Polygenic Traits


Traits that are controlled by
Ex. height, weight, hair color, eye color,& skin color
Skin Color - At least 7 different Genes make up skin color!
Sex-Linked Traits


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
Carried on
chromosomes (X and Y)
Most are
& on X chromosome
 Color blindness,
Affect men more than
 Men have only
X chromosome
Women can be
or affected
Sex Chromosomes for Female are:
Sex Chromosomes for male are:

Fruit fly eye Color
R = Red eyes
r or w = white eyes
What is the probability of having a white eyed male?
 A female fruit fly that is homozygous for red eyes mates with a male who has white eyes. What is the
probability of having a female with white eyes?
5

A woman who is heterozygous for colorblindness has a son with a man who is colorblind. What is the
probability that their son will be colorblind?
Polyploidy

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extra chromosomes.
= normal number of chromosomes
Humans 46 chromosomes/ 23 pairs
= half the number of chromosomes
Sperm or Egg 23 chromosome

(3n)– 3 complete sets of chromosomes.
46 + 23 = 69

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Most plants are polyploidy; sometimes earthworms and goldfish;
Humans always Lethal!
: photographic arrangement of a complete set of chromosomes


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Chromosomes # 1-22 are
Chromosomes # 23 are the
Looking at a karyotype you can see a

Chromosomal
chromosomes

Homologous chromosomes ________________ during MEIOSIS = _________________________

One cell gets 2 copies of the chromosome the other cell gets none.

Nondisjunction can lead to:
(body chromosomes)
.
.
change in the __________________ or

Down syndrome (=____________):

Turner syndrome ____ :

Klinefelter syndrome XXY:
of
(Can be XXy, XXXy, or XXXXy)
Obtaining Fetal Cells - ~Making a Karyotype~
1.
2.
: sample of fluid around baby
: sample of tissue from the placenta
6
: chart that tracks the inheritance of a trait through multiple generations

Generation Symbols
 P=
 F =
of P generation
1

F =
2

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= female
= male
Completely shaded =
Half shaded =

Dominant Disorder Example:
of F generation
1
Appears in ________________ generation

Recessive Pedigree Example:
____________ generations.
Create A Pedigree:

One couple has a son and a daughter with normal pigmentation. Another couple has one son and two
daughters with normal pigmentation. The daughter from the first couple has three children with the
son of the second couple. Their son and one daughter have albinism; their other daughter has normal
pigmentation.
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