MCDB 2150 Fall 2000 Review Questions

Revised December 9, 2000

Lecture 38: Continuous Variation, Polygenic Inheritance

Because of time limitations, only questions 1 through 7 were covered in enough detail to be included in the final examination.

1. What characteristics of wheat make it particularly useful in studies on quantitative genetics?

2. Distinguish between additive alleles and those that exhibit dominance, and explain how allelic interaction determines phenotype in each case.

3. Explain how five different shades of color can be achieved with just two alleles each at two loci.

4. What characteristics must be possessed by a set of genetic loci in order for the principles of quantitative genetics to be applied to them?

5. How would you determine the theoretical number of different phenotypes and their phenotypic ratios for n different additive genetic loci?

6. What factors usually limit the number of different phenotypes that can be distinguished in polygenic inheritance?

7. What prevents application of the concepts of quantitative genetics to the study of traits that are controlled by dominant and recessive alleles?

Items below this line will not be included on the final examination.

8. Describe the difference between discontinuous and continuous variation.

9. Distinguish among mean, median, and mode in a manner that makes it clear you know what each is and how they differ.

10. How does a distribution with low variance differ from one with high variance?

11. What is the difference between a skewed distribution and a normal distribution?

12. What is meant by the concept of heritability when it is applied to a phenotypic trait that is influenced by polygenic inheritance?

13. Briefly define each of the following and explain its significance.

a. Transgressive segregant
b. Bimodal distribution
c. Hybrid vigor
d. Inbreeding depression
e. Quantitative trait locus
14. Describe possible patterns of interaction between genotype and environment.

15. What factors tend to limit the amount of phenotypic change that can be achieved by selection?

16. What factors do you think are causing average human height to be taller now than a few hundred years ago? (This calls for speculation on your part based on what you should have learned about continuous variation. Also, several different factors may be implicated.)

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