Question

In a fruit fly experiment, two grey bodied fruit flies produce mostly grey bodied offspring, but some offspring have black bodies.
i) If there are 280 offspring, how many do you predict will have grey bodies and how many will have black bodies?
ii) How many of the 280 off spring, do you predict, will be heterozygous?
I got the first question, but I don't know about the second :/

Answer 1

What inheritance pattern did you assume the experiment and what genotype did you assume for the P-generation?
Depending on what you assumed, use the statistics obtained from the cross in the P-generation and apply those statistics to the experiment.

Answer 2

I assumed it's 3:1 because it makes sense, but I don't know how to assume genotypes from the information given?

Answer 3

Well. if you assume it was 3:1 then it has to be a double heterozygous cross and the treat is autosomal dominant:

3:1 in phenotype, but the genotype is 1:2:1

Answer 4

let me tell you what i did;
i) 3/4 x 280= grey bodies
1/4 x 280= black bodies
ii) I checked the answer key and it says the heterozygous genotype has a ratio of 2/4?!

Answer 5

That is also correct. Look at the diagram I made... how many has "Aa"?

Answer 6

Ohhhh, I get it now. You know it's Aa x Aa because of the assumption (3:1) right?

Answer 7

Exactly. Or the (3:1) assumption tells me the P-genetration must both be heterozygous and using that information I can find the genotype distribution.

If both was homozygous then it would be 4:0
Homozygote dominant and hetrozygote: 4:0
Homozygote ressicive and hetrozygote: 2:2

Answer 8

Thank youuuu :)

Answer 9

No problem. :)