Hello, I was hoping someone could explain/ show the work for this problem. Our t

Question

Hello, I was hoping someone could explain/ show the work for this problem. Our teacher only showed us how to get to map units when given the numbers of offspring for each phenotype, but not the other way around, so I have no idea how they got those numbers. Please help! :)

Question 3 While working with a type of beetle that is normally smooth, large, and white, you discover three mutations that lead to the recessive phenotypes bumpy, small, and grey, respectively. You cross true-breeding smooth white beetles to true-breeding bumpy grey beetles and get all smooth white F1 beetles. Then you cross the F1 beetles to true-breeding bumpy grey beetles and, after analyzing 800 F2s, calculate a map distance of 5 cM between the smoothness and color loci. a) What are the four phenotypic classes you got in the F2, and about how many of each did you get? For the body type e., smooth or bumpy) use B or b to designate the alleles. For the color (i.e., white or grey) use G or g to designate the alleles. For the size (i.e arge or small) use L or l to designate the alleles *In each case, use the uppercase letter for the associated with the dominant phenotype and the lower case letter for the allele associated with the recessive phenotype Genotypic class Phenotypic class How many of this phenotype Bbgg Smooth White 380 bbGg 380 Bumpy Grey bbGb Smooth Grey 20 bbgg Bumpy White 20

Explanation / Answer

Since the F1 generation was all smooth and white lets suppose that the following alleles represent the phenotypes:

B is for smooth, b is for bumpy

g is for white and G is for grey

True breeding smooth white beetles will have the genotype BBgg and true breeding bumpy grey beetle will have the genotype bbGG. Now the cross between the two will give:

Parent:

BBgg X bbGG

F1:

BbGg

Now all the F1 individuals will be white and smooth.

Now crossing F1 individuals with true breeding bumpy grey individuals we get:

BbGg X bbGG

This cross will lead to genotypes as shown:

Bbgg smooth and white

bbGg bumpy and grey

bbGb smooth and grey

bbgg bumpy and white

The number of individuals in each class will be:

Bbgg- 380

bbGg- 380

bbGb- 20

bbgg- 20

This is how the numbers are obtained.

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