Download Review and Non-Mendelian Genetics

Bookend
1. In a heterozygous tall plant, the
____________ trait shows. It is
represented by a _________ letter. ( T )
2. Tt is a tall or short plant.
3. The ___________ allele does not show in
heterozygous individual ( t ).
4. It is ‘covered’ or ‘hidden’ by the _________
allele.
5. The genotype or phenotype is the letters
that stand for the versions of the genes.
Dominant/Recessive
1. In a heterozygous individual, the
dominant trait shows
2. Represented by a capital letter T
3. Tt is a tall plant
4. The recessive allele does not show in
heterozygous individual
5. It is ‘covered’ or ‘hidden’ by the dominant
allele.
6. The genotype is the letters that stand for
the versions of the genes.
(Go to SASinschool)
Genetics Review of
Punnett Squares
And
Incomplete dominance
Codominance
Multiple Alleles
Polygenic inheritance
And
Sex determination
Punnett Squares
• Are used to find the possible genotypes of
the offspring (children) of a mating
• Also to find the probability of each
genotype occurring
• Each child (mating) is a new occurrence…
each child has the same chance as
previous children.
Probability Ratios
Homozygous . Heterozygous. Homozygous
Dominant
.
. Recessive
1TT
2Tt
1tt
25%
50%
25%
Dominant Phenotype: Recessive Phenotype
3 Tall
:
1 Short
75%
25%
Generation
1. P = Parental = first parents observed
(usually homozygous)
2. F1 = First filial = first children of P
generation
3. F2 = Second filial = Children of F1,
grandchildren of P
Draw the Punnett square and
answer the question
1. A student crosses two true (pure)
breeding pea plants. One has yellow pods
and the other has green pods. Yellow is
dominant to green.
Parent plant genotypes ____ X ____
Draw Punnett square.
What phenotypic results will the student find
in the F1 generation?
Draw the Punnett square and
answer the question
2. Guinea pig coat color is determined by a
single gene. The allele for black coat color
is dominant to brown. In a cross between
two black-haired guinea pigs, 20 offspring
are born. If both parents were
heterozygous, probability would predict
that approximately how many of the 20
offspring would have brown hair?
Answer the Question
3. What term describes an allele whose
characteristic phenotype is masked by the
presence of a second, different allele?
Draw the Punnett square and
answer the question
4. Fifty percent of the offspring produced by
a cross between pea plants have seeds
with a wrinkled (r) appearance caused by
the presence of a homozygous recessive
gene. What were the genotypes of the
parents?
Incomplete Dominance
• In the heterozygous individual the
phenotype is roughly halfway between the
homozygous phenotypes
In Snapdragons
Red X White -> Pink
RR X R’R’ or
CRCR X CWCW -> CRCW
Codominance
•
•
•
•
Both alleles are expressed (show)
AB Blood groups
Checkered chickens
Roan Horses
• Denoted with Capital letter with super
script IAIB
Blood Groups
A = IA
B = IB O = i
Multiple Alleles
• 3 or more possible alleles
• Blood Type Alleles IA, IB, i
• Each individual gets only 2
alleles, one on each homologous
chromosome
Polygenic Inheritance
• 2 or more genes controlling the
same trait
• Traits vary continuously
• Hair color
• skin color
• height
Determining Sex
• Females are XX, Males are XY
• Females have two full sized X
chromosomes
• Males have one full sized X and one small
Y chromosome.
The father determines the sex of
the child by supplying the X or Y
Sex linked Genes
•
•
•
•
Genes on the X chromosome
Hemophilia
Color Blindness
Muscular Dystrophy
Sex linked Continued
• Seen most often in men because they
carry only 1 X chromosome
• The trait only shows in women if they are
homozygous
• Women are usually carriers
• Boys inherit the X chromosome from their
mother
• Girls must inherit it from both parents
Bookend
1. Rr is ____________ for red color.
2. R1R2 is a genotype for __________
dominance and would result in a pink flower
3. AB blood group is an example of
___- dominance.
4. A, B, O blood groups are an example of
___________ ___________
5. Girls normally have 2 ___ chromosomes
6. Boys normally have 1 ___ and 1 ___
chromosome.