Ch.7 Flashcards
Linkage
When genes are located close to each other on the same chromsome
crossing over between homologous chromosomes during…
Prophase I
more prevalent parental allele combinations reflect genes that are…
transmitted on the same chromosome (linkage)
less common offspring classes can be explained by …
crossing over or recombination
Do linked genes assort independently?
no!- they are linked meaning they are on the same chromosome
progeny that exhibit mixing of maternal and paternal alleles on a single chromosome are called
recombinant
when completely linked, how many allele combinations are expected in the gametes
2
genes are completely linked if…
they are on the same chromosome and are close enough together that recombination does not randomize their arrangement
In unlinked genes: what is the ratio of nonrecombinant to recombinant
1/2 nonrecombinant (what we crossed) to 1/2 recombinant (new combinations)
In complete linkage: what is the rate of nonrecombinant to recombinant progeny
only nonrecombinant progeny are produced
what is the ratio of nonrecombinant to recombinant progeny in linked genes with crossing over
mostly nonrecombinant progeny, only a small proportion recombinant
recombination frequency tells you
how far apart two loci are on a chromosome
The farther apart 2 genes are, the more likely
a recombination event will occur between them
How do we calculate recombination frequency?
recombinant offspring/ total offspring
x
100
Genetic distance is proportional to
physical distance (between genes on a chromosome) but they are not identical
