Chapter 4 - Mapping Eukaryote Chromosomes by Recomination

Question 1

recombination map

Answer 1

map loci of genes that were identified by mutant phenotypes showing single-gene inheritance

Question 2

what does it mean if two genes are “linked” ?

Answer 2

loci of genes are on the same chromosome and the alleles on any one homolog are physically “linked” by the DNA between them

Question 3

what is a diagnostic for linkage:

Answer 3

two equally frequent non-recombinant class totalling in excess of 50%
two equally frequent recombinant classes totalling less than 50%

Question 4

crossing over

Answer 4

breakage of two DNA molecules at the same position and their rejoining in two reciprocal recombinant combinations

Question 5

combination products

Answer 5

two new combinations resulting from “cross-over’s”

Question 6

how are recombinants produced from linked genes?

Answer 6

by crossovers which can be visibly observed by formation of chiasmata’s

Question 7

cross-over’s only occur between:

Answer 7

two non-sister chromatids

Question 8

what is the standard genetic test for linkage

Answer 8

a dihybrid test cross to test for deviations from expected 1:1:1:1 phenotype proportions