Question

Imagine that you just went to the pet store and bought two black guinea pigs that are known to be heterozygous (Bb). You also know that black fur (BB) is dominant over white fur (bb), and that a lethal recessive allele is located only one cM away from the recessive b allele. You decide to start raising your own guinea pigs, but after mating these animals several times, you discover they produce only black progeny.

What is the probability of your two black guinea pigs producing a white offspring? Include all possible genotypes of white offspring.

If an average mating produces 10 offspring, how many matings would it take to produce a white offspring?

Answer 1

The two heterozygous guineapigs, when crossed, will have the following result:

Bb x Bb

BB Bb Bb bb

So, from the cross, it is evident that there will be 1 homozygous black far guineapig, 2 heterozygous black fur guineapigs and 1 while fur guineapig. So the probability is 1/4 = 0.25 %. But since a lethal recessive allele is near the recessive allele b, then maybe they re linked or co-expressed and as a result of which there is no white fur guineapig.

If in average mating there are 10 offsprings then there is a probability of 25% chance or 2.5 offsprings to be white. But if this recessive gene is linked with a lethal allele then there will never be a white fur guineapig since it would die.