Correct option is C
Correct Answer:
Option (3) – 14 mu
Explanation :
Let the number of PD asci be x.
Given PD = TT, so TT = x.
Given TT is 12 times NPD, so NPD = x/12.
Total asci = x + x + x/12 = 25x/12
Recombinant fraction in tetrad analysis is calculated as:
(½ × TT + NPD) / total asci
So, recombinant fraction = (½ × x + x/12) / (25x/12)
= (7x/12) / (25x/12)
= 7/25
Recombination percentage = 28%
For Neurospora unordered tetrads, map distance = recombination percentage ÷ 2
Therefore, distance = 28 ÷ 2 = 14 map units
Information Booster :
· Tetrad analysis allows direct estimation of recombination events.
· Tetratype asci represent single crossover events.
· Non-parental ditype asci arise from double crossovers or independent assortment.
· Genetic distance is half the recombination percentage in fungal tetrad analysis.
Additional Information (Incorrect Options):
6 mu and 7 mu: Underestimate the contribution of tetratypes.
28 mu: Represents recombination frequency, not corrected map distance.
