There are two alleles (A and a) for gene A in bread mold (Neurospora crassa). Wi
ID: 259821 • Letter: T
Question
There are two alleles (A and a) for gene A in bread mold (Neurospora crassa). With A, the ascospores could be dyed to red. With a, the ascospoes cannot be dyed to red and remain as colorless. Two haploid cells mate with each other and their progeny asci are dyed with the following result Pattern 1 Pattern 2Pattern 3 Pattern 4 Pattern 5 Pattern6 Red Red Colorless Red Colorless Red Red Red Colorless ColorlessRed Red Red Colorless Red Colorless Red 1st (top) ascospores 2nd ascospores 3rd ascospores 4th ascospores 5th ascospores 6th ascospores 7th ascospores 8th (bottom) ascospores Colorless Colorless Red Colorless Colorless Colorless Colorless Colorless Colorless Red Red ColorlessRed Colorless Red Red Red Colorless Colorless Red Red Colorless ColorlessRed Colorless Colorless Red Colorless Red Colorless Red Observed # of asci 30 82 34 29 27 1) What are the genotypes of the two parental cells? 2) Calculate the distance between gene A and the centromereExplanation / Answer
1. As the neurospora is a haploid organism, each cell contains one copy of the gene. So, the colored genotype is A and the colorless genotype a.
2. The distance between the gene and centromere = 1/2 x second division segregation asci/ total number of asci X 100.
= 1/2 (30 + 34 + 29 + 27) / 279 X 100 = 21.5 cM.