Comprehension Questions

* 1. What does the term recombination mean? What are two causes of recombination?

* 2. In a testcross for two genes, what types of gametes are produced with (a) complete linkage, (b) independent assortment, and (c) incomplete linkage?

3. What effect does crossing over have on linkage?

4. Why is the frequency of recombinant gametes always half the frequency of crossing over?

* 5. What is the difference between genes in coupling configuration and genes in repulsion? What effect does the arrangement of linked genes (whether they are in coupling configuration or in repulsion) have on the results of a cross?

6. How does one test to see if two genes are linked?

7. What is the difference between a genetic map and a physical map?

* 8. Why do calculated recombination frequencies between pairs of loci that are located relatively far apart underestimate the true genetic distances between loci?

9. Explain how one can determine which of three linked loci is the middle locus from the progeny of a three-point testcross.

*10. What does the interference tell us about the effect of one crossover on another?

11. List some of the methods for physically mapping genes and explain how they are used to position genes on chromosomes.

12. What is a lod score and how is it calculated?

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