Exam 2 Content

law of independent assortment

alleles of different genes segregate independently of each other in gametogenesis

linked genes

genes that are close together on the same chromosome

complete linkage

impossible for genes to be independently assorted

cis (coupling)

mutant alleles of both genes on the same chromosome (ab/AB)

trans (repulsion)

mutation alleles are on different homologues of the same chromosome (Ab/aB)

recombinant

chromosomes that are formed from crossing over

parental combinations

original homologues from parents, usually are a higher number of gametes compared to recombinants

recombination frequency

sum of recombinant types/sum of all progeny, if <50% then genes are linked, if =50% then genes are unlinked, smaller values means genes are closer together on a chromosome, is independent of allele configuration

linkage group

all known genes on a chromosome

gene mapping

a method using recombination frequencies between alleles to determine relative distance

map unit

equivalent to 1% recombination (in short distances ) or 1 centimorgan

pairwise comparisons

comparisons of multiple pairs of genes on the same chromosome to place genes relative to each other

multiple cross-overs

if recombination rate between two genes is <10%, double cross-overs are highly unlikely, can use three-point crosses to investigate these

nonrecombinant

two most frequent types of gametes in any genetic cross

double-recombinant

two rarest types of gametes in a genetic cross, exchanges middle pairs of alleles between chromosomes