Please Explain. 1. What is the recombination frequency between ec and cv? Answer
ID: 146870 • Letter: P
Question
Please Explain. 1. What is the recombination frequency between ec and cv? Answer is 0.105 2. The expected frequency of double recombination gametes in this data set are: Answer is 0.0095 3. The coefficient of coincidence for this data set is: Question 20-24: In 1926 Calvin Bridges published the following three-point test cross of the scute (sc) crossveinless (cv) and echinus eyes (ec) X-linked genes: Female Male F2 Gamete Classes Progeny sc-, cv-, ec- sc+, cv+, ec+ sc-, cv+, ec+ sct, cv-, ec- sc-, cv+, ec- sc+, cv-, ec+ sc-, cv-, ec+ sc+, cv+, ec- Total 1158 1455 163 130 192 148 3248Explanation / Answer
Answer:
Female genotype = sc+ cv+ ec / sc- cv- ec-
1).
If single crossover occurs between sc+&..v+
Normal combination: sc+ cv+ / sc- cv-
After crossover: sc+ cv- / sc- cv+
sc+ cv- progeny= 130+148 = 278
sc- cv+ progeny = 163+192= 355
Total this progeny = 633
The recombination frequency between sc+ & cv+ = (number of recombinants/Total progeny) 100
RF = (633/3248)100 = 19.49%
2).
If single crossover occurs between cv+ & ec+..
Normal combination: cv+ ec+ / cv- ec-
After crossover: cv+ ec- / cv- ec+
cv+ ec- progeny= 192+1= 193
cv- ec+ progeny = 148+1=149
Total this progeny = 342
The recombination frequency between cv+&ec+ = (number of recombinants/Total progeny) 100
RF = (342/13248)100 = 10.53%
3).
If single crossover occurs between sc+&ec+..
Normal combination: sc+ ec+ / se- ec-
After crossover: sc+ ec- / sc- ec+
sc+ ec- progeny= 130+1= 131
sc- ec+ progeny = 163+1=164
Total this progeny = 295
The recombination frequency between sc+ec+ = (number of recombinants/Total progeny) 100
RF = (295/3248)100 = 9.08%
Recombination frequency (%) = Distance between the genes (cM)
sc+----------9.08cM--------ec+-----------10.53cM--------------cv+
Expected double crossover frequency = (RF between sc+ & ec+) * (RF between ec+ & cv+)
= 9.08% * 10.53% = 0.0096
The observed double crossover frequency = 1+1 / 3248 = 0.0006
Coefficient of Coincidence (COC) = Observed double crossover frequency / Expected double crossover frequency
= 0.0006 / 0.0096
= 0.0625 0r 0.0630