Question

In Neurospora, the arrangement of ascospore after meiosis is found to be 2a : 4A : 2a. What can be concluded?

• A. First reductional then equational division
• B. First equational and then reductional division
• C. Both occur simultaneously
• D. Nothing can be concluded

Answer 1

The correct option is A First reductional then equational division

Neurospora produces ordered tetrads as product of meiosis which allows detection of products of first and second segregation division. A cross between normal (A) and mutant (a) strain produces a linear arrangement of four normal spores (4 A) followed by four mutant spores (4 a). Crossing over between centromere and gene at four strand stage leads to 2 A : 2a : 2A : 2a or 2a : 4A : 2a arrangement. This means that reductional division is followed by equational division; if mitosis was the first division, the cross over would have occurred at two strand stage and spores arrangement would be 4a : 4A; option B is incorrect. A cell can not undergo both divisions simultaneously; option B is incorrect. Correct answer is option A.