1. Understanding Inheritance

2. Punnett Squares
A Punnett Square is a model that can be used to predict the possible genotypes and phenotypes of the offspring of two parents.

3. Punnett Square
B= black fur
b= brown fur

4. Punnett Square
Female parent= BB Male parent= bb B

5. Punnett Square
Female parent= BB Male parent= bb B B

6. Punnett Square
Female parent= BB Male parent= bb B B b

7. Punnett Square
Female parent= BB Male parent= bb B B b b

8. Punnett Square
Female parent= BB Male parent= bb B B B b b b

9. Punnett Square
Female parent= BB Male parent= bb B B B b B b b b

10. Punnett Square
Female parent= BB Male parent= bb B B B b B b b b B b

11. Punnett Square B B B b B b b b B b B b
Female parent= BB Male parent= bb B B B b B b b b B b B b

12. Punnett Square B B B b B b b b B b B b
Female parent= BB Male parent= bb B B B b B b b
black
black b B b B b
black
black

13. Punnett Square A cross between two homozygous pea plants
One with yellow seeds (YY)
One with green seeds (yy)

14. Punnett Squares All offspring have the heterozygous genotype
All offspring have the yellow phenotype
These offspring are called hybrids because they have one of each allele

15. Punnett Squares
A cross between two heterozygous genotypes (Yy and Yy)

16. Punnett Squares
The offspring would have 3 different genotypes and 2 different phenotypes.

17. Punnett Squares Cross a freckled Dad (Ff) with a freckled Mom (Ff)
F= freckles
f= no freckles

18. Punnett Squares Genotypes are FF Ff ff Ff F f F f _____ % FF
F= freckles
f= no freckles 25 F FF Ff 50 25 f ff Ff

19. Punnett Squares Phenotypes are FF Ff ff Ff F f F f _____ % Freckles
_____ % No freckles
F= freckles
f= no freckles F FF Ff 75 25 f ff Ff

20. Incomplete Dominance
Occurs in a heterozygous individual when the dominant allele is not completely expressed over the recessive allele
Results in a blend of the two parent phenotypes

21. Incomplete Dominance
Common in:
Flower color
Eye color
Skin color

22. Codominance
Occurs when both alleles can be observed because both are dominant.
Example: Cow color
RR= red
WW= white
RW= roan (red and white)

23. Codominance Example: Horse color GG= gray WW= white
GW= Apaloosa (white with gray spots)

24. Codominance
The human blood type AB is a codominant trait because blood type A and B are both dominant.

25. Multiple Alleles Some genes are controlled by more than two alleles.
Human blood type is determined by 3 different alleles
IA= Type A blood (dominant)
IB= Type B blood (dominant)
i= type O blood (recessive)

27. Sex-Linked Inheritance
One pair of human chromosomes determines sex.
Two X chromosomes: female
One X and one Y chromosome: male

28. Sex-Linked Inheritance
Some genes are carried on the X chromosome.
If a male gets a recessive allele of an X- linked gene, then he will have the recessive trait (because he has no allele on the Y chromosome to “hide” the recessive trait).

29. Sex-Linked Inheritance
Common sex-linked traits
Hemophilia
Color blindness

30. Sex-Linked Inheritance
A carrier has one recessive allele.
They don’t have the trait but they can pass on the trait.

31. Polygenic Inheritance
When more than one gene determines the phenotype of a trait
Many phenotypes are possible in polygenic inheritance
Examples in humans: eye color, skin color, height

32. Genetic Disorders
If a change occurs in a gene, it is called a mutation.
Inherited mutations can cause a genetic disorder.

34. Genes and the Environment
An organism’s environment can affect its phenotype
Genes affect heart disease, but so does diet and exercise
Genes affect skin color, but so does exposure to sunlight

35. Punnett squares model the ___ of offspring.
Genotypes
Phenotypes
Genotypes and Phenotypes
Genes

36. Polygenic inheritance
What is it called when alleles produce a phenotype that is a blend of the parents’ phenotypes?
Incomplete dominance
Codominance
Multiple alleles
Polygenic inheritance

37. How many Y chromosomes do females have?1 2 3

38. Why are males more likely to be colorblind than females?
Maternal inheritance
Sex-linked inheritance
Polygenic inheritance
Incomplete dominance

39. If two plants with genotype Mm are crossed, what % of the offspring will have the dominant phenotype? 0%
25%
50%
75%

40. What is it called when more than one gene determines a trait?
Incomplete dominance
Codominance
Polygenic Inheritance
Sex-linked inheritance