1. Bookend
In a heterozygous tall plant, the ____________ trait shows. It is represented by a _________ letter. ( T )
Tt is a tall or short plant.
The ___________ allele does not show in heterozygous individual ( t ).
It is ‘covered’ or ‘hidden’ by the _________ allele.
The genotype or phenotype is the letters that stand for the versions of the genes.

2. Dominant/Recessive
In a heterozygous individual, the dominant trait shows
Represented by a capital letter T
Tt is a tall plant
The recessive allele does not show in heterozygous individual
It is ‘covered’ or ‘hidden’ by the dominant allele.
The genotype is the letters that stand for the versions of the genes. (Go to SASinschool)

3. Genetics Review of Punnett Squares
And
Incomplete dominance
Codominance
Multiple Alleles
Polygenic inheritance
Sex determination

4. 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.

5. Probability Ratios Homozygous . Heterozygous . Homozygous
Dominant Recessive
1TT 2Tt 1tt
25% 50% 25%
Dominant Phenotype: Recessive Phenotype
3 Tall : 1 Short
75% %

6. Generation P = Parental = first parents observed (usually homozygous)
F1 = First filial = first children of P generation
F2 = Second filial = Children of F1, grandchildren of P

7. 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?

8. 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?

9. Answer the Question
3. What term describes an allele whose characteristic phenotype is masked by the presence of a second, different allele?

10. 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?

11. 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

12. Codominance Both alleles are expressed (show) AB Blood groups
Checkered chickens
Roan Horses
Denoted with Capital letter with super script IAIB

13. Blood Groups A = IA B = IB O = i

14. Multiple Alleles 3 or more possible alleles
Blood Type Alleles IA, IB, i
Each individual gets only 2 alleles, one on each homologous chromosome

15. Polygenic Inheritance
2 or more genes controlling the same trait
Traits vary continuously
Hair color
skin color
height

16. 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.

17. The father determines the sex of the child by supplying the X or Y

18. Sex linked Genes Genes on the X chromosome Hemophilia Color Blindness
Muscular Dystrophy

19. 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

21. Bookend Rr is ____________ for red color.
R1R2 is a genotype for __________ dominance and would result in a pink flower
AB blood group is an example of ___- dominance.
A, B, O blood groups are an example of ___________ ___________
Girls normally have 2 ___ chromosomes
Boys normally have 1 ___ and 1 ___ chromosome.