Genes A , B , and C are linked on a chromosome and found in the order A-B-C. Gen
ID: 259613 • Letter: G
Question
Genes A, B, and C are linked on a chromosome and found in the order A-B-C. Genes A and Brecombine with a frequency of 10%, and genes Band C recombine at a frequency of 27%. For the cross a +b +c /abc+ × abc / abc, predict the frequency of progeny. Assume interference is zero.
1. Predict the frequency of a+b+c progeny
2. Predict the frequency of abc+ progeny
3. Predict the frequency of a+bc+ progeny
4. Predict the frequency of ab+c progeny
5. Predict the frequency of a+b+c+ progeny
6. Predict the frequency of abc progeny
7. Predict the frequency of a+bc progeny
8. Predict the frequency of ab+c+ progeny
Explanation / Answer
Answer:
1. The frequency of a+b+c progeny= 32.85%
2. The frequency of abc+ progeny=32.85%
3.The frequency of a+bc+ progeny=3.65%
4. The frequency of ab+c progeny=3.65%
5. The frequency of a+b+c+ progeny = 12.15%
6. The frequency of abc progeny=12.15%
7. The frequency of a+bc progeny=1.35%
8. The frequency of ab+c+ progeny=1.35%
Explanation:
If interference is zero, observed double crossover is equal to expected double crossover.
Expected double crossover = (Single crossover frequency (SCO) b/w A&B) x (Single crossover frequency (SCO) b/w B&C)
= 0.1 * 0.27 = 0.027
Class of gametes
Phenotype
Frequency of reciprocal pair
Numbers
Frequency of each class
Number of progeny frequency * 100 = %
Parental
a+b+c
1- all recombinant progeny
1-(0.073+0.243+0.027) = 0.657
0.3285
32.85%
abc+
0.3285
32.85%
SCO 1
a+bc+
RF in region 1 = SCO1 - DCO
SCO1 = 0.1 – 0.027 = 0.073
0.0365
3.65%
ab+c
0.0365
3.65%
SCO 2
a+b+c+
RF in region 2 = SCO2 - DCO
SCO2 = 0.27 – 0.027 = 0.243
0.1215
12.15%
abc
0.1215
12.15%
DCO
A+bc
(RF in region 1) * (RF in region 2)
0.1 * 0.27 = 0.027
0.0135
1.35%
ab+c+
0.0135
1.35%
Class of gametes
Phenotype
Frequency of reciprocal pair
Numbers
Frequency of each class
Number of progeny frequency * 100 = %
Parental
a+b+c
1- all recombinant progeny
1-(0.073+0.243+0.027) = 0.657
0.3285
32.85%
abc+
0.3285
32.85%
SCO 1
a+bc+
RF in region 1 = SCO1 - DCO
SCO1 = 0.1 – 0.027 = 0.073
0.0365
3.65%
ab+c
0.0365
3.65%
SCO 2
a+b+c+
RF in region 2 = SCO2 - DCO
SCO2 = 0.27 – 0.027 = 0.243
0.1215
12.15%
abc
0.1215
12.15%
DCO
A+bc
(RF in region 1) * (RF in region 2)
0.1 * 0.27 = 0.027
0.0135
1.35%
ab+c+
0.0135
1.35%
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