BIOL241, 2013 Name:_____________________
Quiz 2 (20 points) Purdue ID:__________________
1) Chromosome 3 of wheat carries three loci (a, b, and c). A testcross of triple recessives with F1 plants heterozygous for
...
BIOL241, 2013 Name:_____________________
Quiz 2 (20 points) Purdue ID:__________________
1) Chromosome 3 of wheat carries three loci (a, b, and c). A testcross of triple recessives with F1 plants heterozygous for the three genes yields progeny having the following genotypes:
a) What is the gene sequence of the chromosome (3 points)?
b) What are the map distances between the genes (4 points)?
Distance between b and a is: (74+66+24+16)/1000 = 18 m.u.
Distance between a and c is: (126+114+24+16)/1000= 28 m.u.
c) What are the values for coefficient of coincidence and interference (3 points)?
2) A Neurospora cross was made between a strain that carried the mating-type allele A and the mutant allele arg-1 and another strain that carried the mating-type allele a and the wild-type allele for arg-1 (+). Four hundred linear octads (shown as tetrads) were isolated, and they fell into the seven classes given in the table below.
a) Deduce the linkage arrangement of the mating-type locus and the arg-1 locus. Include the centromere or centromeres on your map. Label all intervals in map units (8 points).
A to centromere: ½(36+2+4+6)/400 = 6 m.u.
arg to centromere: ½(100+2+4+6)/400 = 14 m.u.
Because PD = NPD, A and arg are on different chromosomes.
6 m.u. 14 m.u.
0----------------A----- 0---------------------arg-------
b) Diagram the meiotic divisions that led to class 6 (2 points).
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