Two fruit bats are crossed in a captive breeding program. It is a testcross invo
ID: 164184 • Letter: T
Question
Two fruit bats are crossed in a captive breeding program. It is a testcross involving three loci that control for different traits: Fur color (Ff = purple, ff = blue), Ear size (Ll = large, ll = small), and Fruit Preference (Aa = avocados, aa = mangos). The phenotypes and numbers of offspring in each category are shown below.
Phenotype
Genotype
# of Offspring
Class
Purple, large, avocado-loving
Ff, Ll, Aa
1
Double crossover
Purple, large, mango-loving
Ff, Ll, aa
558
Parental
Purple, small, avocado-loving
Ff, ll, Aa
56
Single crossover
Purple, small, mango-loving
Ff, ll, aa
70
Single crossover
Blue, large, avocado-loving
ff, Ll, Aa
62
Single crossover
Blue, large, mango-loving
ff, Ll, aa
53
Single crossover
Blue, small, avocado-loving
ff, ll, Aa
497
parental
Blue, small, mango-loving
ff, ll, aa
3
Double crossover
Calculate the coefficient of coincidence and the interference for this cross. Remember: CoC = observed DCO/expected DCO and Interference = 1 - CoC
Phenotype
Genotype
# of Offspring
Class
Purple, large, avocado-loving
Ff, Ll, Aa
1
Double crossover
Purple, large, mango-loving
Ff, Ll, aa
558
Parental
Purple, small, avocado-loving
Ff, ll, Aa
56
Single crossover
Purple, small, mango-loving
Ff, ll, aa
70
Single crossover
Blue, large, avocado-loving
ff, Ll, Aa
62
Single crossover
Blue, large, mango-loving
ff, Ll, aa
53
Single crossover
Blue, small, avocado-loving
ff, ll, Aa
497
parental
Blue, small, mango-loving
ff, ll, aa
3
Double crossover
Explanation / Answer
Answer:
a). Heterozygous genotype; PmL/pMl
Alleles, PLm present on one chromosome and alleles, plM on the other chromosome.
b). Alleles, PL are inherited.
c). The middle loci is M
The order of genes is P----M-----L
Explanation
Purple= P; blue= p
Large= L; Small= l
Manago-loving= m; Avocado-loving= M
Phenotype
Genotypes (short form)
Number of progeny
Purple, large, avocado-loving
PLM
1
Purple, large, mango-loving
PLm
558
Purple, small, avocado-loving
PlM
56
Purple, small, mango-loving
Plm
70
Blue, large, avocado-loving
pLM
62
Blue, large, mango-loving
pLm
53
Blue, small, avocado-loving
plM
497
Blue, small, mango-loving
Plm
3
Total
1587
Parental combinations are more so, the parental combinations PLm/plM
1. If single cross over (SCO) occurs between P & L
Normal order= P --------- L & p ----- l
After cross over= P----- l & p------ L
p ----- l recombinants are 70+56= 126
p ------ L recombinants are 62+53=115
Total recombinants = 241
RF = (241/1300)*100 =18.54%
2. If single cross over (SCO) occurs between L&m
Normal order= L --------- m & l --------- M
After cross over= L ---------M & l ------ m
L ---------M recombinants are 1+62= 63
l ------ m recombinants are 3+70=73
Total recombinants = 136
RF = (136/1300)*100 = 10.46%
3. If single cross over (SCO) occurs between P & m
Normal order= P --------- m & p ----- M
After cross over= P ----- M & p ------ m
P ----- M recombinants are 1+56=57
P ------ m recombinants are 3+53=56
Total recombinants = 113
RF = (113/1300)*100 = 8.69%
% RF = Map unit distance
The order of gene is -----
P ------8.69m.u.------- M -----------10.46 m.u.----------L
Expected double crossover = (0.0869 * 0.1046)/1300 = 0.009
Double cross over= 4/1300 = 0.003
Coefficient of coincidence = 0.003/0.009
= 0.33
Interference = 1- Coefficient of coincidence
= 1- 0.33 = 0. 67
Phenotype
Genotypes (short form)
Number of progeny
Purple, large, avocado-loving
PLM
1
Purple, large, mango-loving
PLm
558
Purple, small, avocado-loving
PlM
56
Purple, small, mango-loving
Plm
70
Blue, large, avocado-loving
pLM
62
Blue, large, mango-loving
pLm
53
Blue, small, avocado-loving
plM
497
Blue, small, mango-loving
Plm
3
Total
1587
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