Chapter 8: Linkage and Chromosome Mapping in Eukaryotes

Question 1

What is linkage?

Answer 1

two genes on a single pair of homologs (chromosomes), which prevents independent assortment and segregation of these genes (when crossing over is not taken into consideration)

Question 2

In complete linkage (linkage without crossing over), the 2 parental gametes are formed in ____ proportions

Answer 2

equal

Question 3

crossover involves only two ____ chromatids of the four chromatids present in the tetrad

Answer 3

nonsister

Question 4

As the distance between the two genes increases, the proportion of recombinant gametes ___1___(increases or decreases) and that of the parental gametes ___2___(increases or decreases)

Answer 4

1) increases

2) decreases

Question 5

when the loci of two linked genes are far apart, the number of recombinant gametes approaches, but does not exceed _____%

Answer 5

50%

Question 6

why will the noncrossover gametes always be more abundant than the crossover gametes?

Answer 6

because crossover doesn’t happen 100% of the time

Question 7

What is the complete linkage ratio and when is it only observed?

Answer 7

1:2:1 genotypic and phenotypic ratio

usually only observed when genes are very close and number of progeny is small