.30 he following tetrads were produced by a cross of a Neuraspora strain that ha
ID: 208823 • Letter: #
Question
.30 he following tetrads were produced by a cross of a Neuraspora strain that had white spores (w) and a nutritional requirement for the amino acid arginine (arg) with a strain that had dark spores and no arginine requirement Spore Pairs Tetrads 4 6 1-2 3-4 arg w arg w arg warg w + w arg w + arg 5-6 +arg+ + arg +arg w arg No. 58 14 15 10 Total = 100 (a) What is the map distance between the arg locus and the cen- tromere? (b) What is the map distance between the w and arg loci? (c) Are the arg and w loci found on the same or dif- ferent arms of the chromosome?Explanation / Answer
a Distance between arg locus and centromere
second division seggregants are in 2,3,4, and 6 columns. They are recombinants
Distance between the gene and the centromere= number of second division segregants divided by total progeny multiplied by 100
14+15+2+10=41
41/100x100=41
Since half the chromatids are involved 41/2=20.5 mapunits is the distance between the gene and the centromere.
b.Column 5 is NPD (non parental ditype)
TT (tetra type (2 parentals and 2recombinations) are in 2,3,4,and 6 columns14+15+2+10=41
Distance between w and arg=(NPD+1/2TT) / 100*100
1+1/2 (41)
1+20.5=21.5mapunits
c. If PD=NPD genes are linked. Since they are not equal arg and w genes are in different arms of the chromosomes. .
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