Question

Assume that an individual is heterozygous for two genes (A and B) that are known to be 20 cM apart.
Assuming that the genes are in coupling, what type of gametes will this individual make and at what expected
frequencies? Show your work.

Answer 1

Coupling denotes that A and B are in cis configuration which means that these are present in one allele together whereas ab are present in another allele. So the parental coupling is AB/ab. Gametes produced in meosis will be either of the parental genotype or recombinant genotype.

If recombination takes place the gametes produced will be: Ab/ aB meaning that A and b will be present on one allele while a and B will be present on the other allele.

Again, the parental combination will be generated as well having AB/ab.

Therefore these arw the two types of gametes formed from A and B genes in cis phase.

Genes are also 20cM apart. So their recomination frequencies will be 20%. So parental frequency will be 100-20% = 80%. So expected frequency of Ab/ aB is 20% while AB/ab gamete is 80%

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