Homework Assignment - Quantitative Genetics
100 points total (25 points each)
Use complete sentences in all of your answers where appropriate. If you are stumped by a problem, explain as much as you can to get partial credit.
1. Discuss the differences between continuous and discontinuous traits. Provide examples for each.
2. Two bean varieties are crossed and the mean seed weight of the F1 population is 311 mg and the variance is 1.5. The F1 plants are selfed, and the mean of the resulting F2 population is 303 mg and the variance is 6.1. Do you have sufficient data to calculate a heritability esitmate? If so, what heritability estimate would it be? Calculate this value if possible.
3. For a large cattle herd, variance components were estimated for the following traits.
| Trait | |||
|---|---|---|---|
| Variance | Shank length | Neck length | Fat content |
| Phenotypic | 310.2 | 730.4 | 106.0 |
| Environmental | 248.1 | 292.2 | 53.0 |
| Additive genetic | 46.5 | 73.0 | 42.4 |
| Dominance genetic | 15.6 | 365.2 | 10.6 |
a. Estimate H2
and h2 for each trait.
b. If selection was placed on this population, for which trait would the
results of selection be the most predictable? Why?
4. A pea breeder in Northern Wisconsin is trying to select for a line which matures earlier. The base population in which the research is being performed has a mean maturity of 100 days. The breeder selected parents that had a mean of 86 days and created a new segregating population. The mean of this population was 93.
a. What is the narrow sense
heritability for days to maturity in this pea population.
b. The breeder now wants to repeat the selection and crossing cycle and
hopes to achieve a population with a mean maturity of 87 days. Assuming
the narrow sense heritability value estimated in section a still is the
same, what should the mean of the parents used in the new crossing cycle
be for the breeder to achieve this goal?