Question

Locus A and Locus B are 48.1 cM apart on the same chromosome. Seven populations of flies (500 individuals each) were determined for the numbers of each type of chromosome (Table below). Which of the populations below is at linkage equilibrium?

	Populations:
Chromosome Type:	1	2	3	4	5	6	7
AB	20	70	120	130	150	220	270
Ab	280	230	180	170	150	80	30
aB	380	330	280	270	250	180	130
ab	320	370	420	430	450	520	570

Answer 1

Linkage equilibrium is the condition when two genes at two loci are independent of each other.

That means the progeny population has 50% of individuals with parental genotype and 50% of individuals with recombinant genotype.

In this case, the locus A and locus B are 48.1cM apart, which means that recombination would be 48.1% only, instead of 50% (highest) in independent genes.

Here the population is 500 individuals in each case, the individuals with recombinant genotype would be 240. And the parental combination would be 260 individuals.

Here, population 3, shows Ab = 180; aB = 280.

Total 180 + 280 = 460

460/2 = 230. Individuals are recombinants.

This ratio is near to linkage equilibrium.