Fertilization between two mating types (P1 and P2) of Neurospora led to a diploid ascus cell, which gave rise to ascus containing 8 haploid ascospores. A set of DNA markers representing two linked loci was analyzed in P1, P2 and the octads labeled 01 to 08 arranged from the tip to the base of the ascus. The observed profile is represented below:

Which one of the following is a correct conclusion of the above observation?

Correct option is B

Explanation-

In Neurospora, ordered tetrads (8 spores) allow us to determine the timing of segregation of alleles:
                  1.  First Division Segregation (FDS) indicates no crossing over between a gene and centromere — alleles separate at Meiosis I.
                  2.  Second Division Segregation (SDS) indicates crossing over occurred — alleles separate at Meiosis II.
Analyzing the DNA marker profiles:
Given banding patterns labeled (a), (b), (c), and (d).
After looking at bands:
(b) shows a 2:2:2:2 pattern: alternating 2 of one type, 2 of another, repeated. This is indicative of second division segregation (SDS) — crossing over happened and alleles segregated in Meiosis II.
(d) shows a 2:2:2:2 pattern too — same reasoning applies.
So, (b) and (d) show identical SDS patterns → they are allelic (variants at the same locus).

Option B is Correct
"Bands labeled (b) and (d) are allelic and segregation occurred during meiosis II."
Allelic → because they represent two different forms of the same gene (each spore gets either b or d).
Meiosis II → because of the 2:2:2:2 banding pattern, indicating crossing over occurred, and the alleles segregated during second meiotic division.