NEET 2022 — Biology solution

NEET2022Biology

The recombination frequency between the genes a & c is 5%, b & c is 15%, b & d is 9%, a & b is 20%, c & d is 24% and a & d is 29%. What will be the sequence of these genes on a linear chromosome ?

A
a, d, b, c
B
d, b, a, c
C
a, b, c, d
D
a, c, b, d

Solution

Recombination frequency is proportional to map distance, so the largest frequency identifies the genes at the extreme ends of the linkage group.

Largest distance: $a$ to $d$ = 29%. So $a$ and $d$ are the end genes.

Place $c$ relative to $a$ : $a$ - $c$ = 5%, so $c$ is 5 units from $a$ .

Place $b$ relative to $c$ : $b$ - $c$ = 15%, so $b$ is 15 units from $c$ in the direction away from $a$ .

Check: $a$ - $b$ = $5 + 15 = 20$ % (matches given), $b$ - $d$ = $29 - 5 - 15 = 9$ % (matches given), $c$ - $d$ = $15 + 9 = 24$ % (matches given).

So the sequence is $a, c, b, d$ .

← Back to full paper

Practice more Biology

Concept-wise practice with instant solutions on Fundamenthol.

Start practicing →