1. Pedigrees & More Genetics

2. Pedigree
Male
Female
Heterozygous
Shows trait

3. 1/2 1/2 2/2 x 1 = 1/2 (1) Aa aa Probabilities
Child will have recessive trait? aa
Chance of “a” allele from dad?
Chance of “a” allele from mom?
Total
1/2
x 1 = 1/2
1/2
2/2
(1)

4. Recessive characteristics
Inheritance pattern
Trait tends to skip generations

5. Dominant characteristics
Trait does not skip generations
Occurs frequently within a family

6. Pedigree Analysis

7. Sex linked characteristics
Tend to occur more in males than in females
Color-blindness
Hemophilia

8. X-linked Recessives: More commonly seen in Males
Why?
Males only need one recessive allele to see trait.
E.g. Color-blindness
XcY = colorblind male
XcXc = colorblind female
XcX = carrier female

9. A woman with normal vision whose father was colorblind marries a colorblind male. What percent of the couple’s sons will be colorblind?
All
75%
50%
25%

10. A woman with normal vision whose father was colorblind marries a colorblind male. What percent of the couple’s sons will be colorblind?
All
75%
50%
25% Xc X
XcXc
XcX Y
XcY XY

11. Incomplete Dominance

12. Codominance &Multiple Alleles

14. Epistasis
A gene at one locus alters the expression of a gene at another locus.
Example:
Black coat (B) is dominant to brown (b)
Pigment color (C) is dominant to no pigment color (c)

15. Polygenic Traits
Additive effect of multiple genes on a single phenotype
Results in normal distribution
Examples: skin color, height

16. Effect of Environment on Phenotype
More acidic soil
Less acidic soil

17. Pleiotropic Effects