Looking for classes? Ksquare Career Institute, Bengaluru →
Two genes R and Y are located very close on the chromosomal linkage map of maize plant. When RRYY and rryy genotypes are hybridized, the F2 segregation will show
A
segregation in the expected 9 : 3 : 3 : 1 ratio
B
segregation in 3 : 1 ratio
C
higher number of the parental types
D
higher number of the recombinant types
Detailed Solution
Genes located on the same chromosome are linked and tend to be inherited together.
The strength of linkage depends on the distance between the genes: the closer the two genes are, the smaller the chance of crossing over between them.
R and Y are located very close together, so they are tightly linked and the chances of crossing over are highly reduced.
The F1 hybrid (RrYy) therefore forms a large number of parental gametes (RY and ry) and only a few recombinant gametes (Ry and rY).
This results in a higher number of parental types in the F2 generation as compared with the recombinant types.
The 9 : 3 : 3 : 1 ratio would be obtained only if the two genes assorted independently, which they do not.
So the F2 segregation will show a higher number of the parental types.
The strength of linkage depends on the distance between the genes: the closer the two genes are, the smaller the chance of crossing over between them.
R and Y are located very close together, so they are tightly linked and the chances of crossing over are highly reduced.
The F1 hybrid (RrYy) therefore forms a large number of parental gametes (RY and ry) and only a few recombinant gametes (Ry and rY).
This results in a higher number of parental types in the F2 generation as compared with the recombinant types.
The 9 : 3 : 3 : 1 ratio would be obtained only if the two genes assorted independently, which they do not.
So the F2 segregation will show a higher number of the parental types.