Question

A plant with genotype AABbCC is selfed, F2 phenetypic ratio would be:-(AIPMT-2002)

a) 9:3:3:1

b) 27:9:9:9:3:3:3:1

c) 1:1

d) 3:1

Kindly answer sir/mam.

Answer 1

The answer is 3:1 becoz:-

when AABbCC is selfed, we get genotypes:-

AABBCC, AABbCC AAbbCC.

Now on taking cases:-

a) crossinng btw AABBCC nd AABbCC

we get AABBCC nd AABbCC only. So we get only dominant phemotype

b) crossing btw AABbCC nd AAbbCC

we get AABbCC nd AAbbCC in ratio 1:1

c) crossing btw AABBCCnd AAbbCC

we get AABbCC only, so only dominant phenotype.

So as we get only 2 phenotypes, nd dominant type is more common

Hope this helps.