47. In a region of chromosome 4 there are three genes, j, k, 1. 110 cM The coeff
ID: 259608 • Letter: 4
Question
47. In a region of chromosome 4 there are three genes, j, k, 1. 110 cM The coefficient of coincidence in this region is 0.8, and it is known that the interference is driven by j-k recombination where recombination between j and k interferes with recombination in the region between k and 1. 20 ?? A true -breeding k is mated with a true-breeding j 1 individual. The resultant triple heterozygote is test crossed. What classes (include phenotypes and proportions) are expected in the next generation if 1000 offspring?Explanation / Answer
Answer:
Coefficient of coincidence = Observed double crossover frequency / Expected double crossover frequency
0.8 = ODCO / 0.02
Expectec double crossover frequency = (Single crossover frequency (SCO) b/w j&k) x (Single crossover frequency (SCO) b/w k&l)
= 10% x 20% = 0.02
Observed double crossover frequency = 0.8 * 0.02 = 0.016 =
+k+ / +k+ x j + l/ j + l------P1
+k+ / j + l-------------F1
+k+ / j + x jkl/jkl ----------------Testcross
Class of gametes
Phenotype
Frequency of reciprocal pair
Numbers
Frequency of each class
Number of progeny frequency * 100 = %
Parental
+k+ /jkl
1- all recombinant progeny
1-(0.084+0.184+0.0) = 0.712
0.356
35.6%
j+l/jkl
0.356
35.6%
SCO 1
++l/jkl
RF in region 1 = SCO1 - DCO
SCO1 = 0.1 – 0.016 = 0.084
0.042
4.2%
jk+/jkl
0.042
4.2%
SCO 2
+kl/jkl
RF in region 2 = SCO2 - DCO
SCO2 = 0.2 – 0.016 = 0.184
0.092
9.2%
j++/jkl
0.092
9.2%
DCO
+++/jkl
(RF in region 1) * (RF in region 2)
0.1 * 0.2 = 0.02
0.01
1%
jki/jkl
0.01
1%
Class of gametes
Phenotype
Frequency of reciprocal pair
Numbers
Frequency of each class
Number of progeny frequency * 100 = %
Parental
+k+ /jkl
1- all recombinant progeny
1-(0.084+0.184+0.0) = 0.712
0.356
35.6%
j+l/jkl
0.356
35.6%
SCO 1
++l/jkl
RF in region 1 = SCO1 - DCO
SCO1 = 0.1 – 0.016 = 0.084
0.042
4.2%
jk+/jkl
0.042
4.2%
SCO 2
+kl/jkl
RF in region 2 = SCO2 - DCO
SCO2 = 0.2 – 0.016 = 0.184
0.092
9.2%
j++/jkl
0.092
9.2%
DCO
+++/jkl
(RF in region 1) * (RF in region 2)
0.1 * 0.2 = 0.02
0.01
1%
jki/jkl
0.01
1%
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