Time for some more xenobiology. In aliens, glossy exoskeleton (G) is dominant to
ID: 314588 • Letter: T
Question
Time for some more xenobiology. In aliens, glossy exoskeleton (G) is dominant to dull exoskeleton (g), excessive drooling (D) is dominant to normal drooling (d), and highly acidic blood (A) is dominant to mildly acidic blood (a). Genetic researchers at Weyland-Yutani Corporation perform a three-point testcross to map the relative locations of these genes. They crossed heterozygotes for all three traits with recessive homozygotes and collect this data:
Observed Number
Glossy, excessive drooling, highly acidic
Dull, normal drooling, mildly acidic
Glossy, excessive drooling, mildly acidic
Dull, normal drooling, highly acidic
Glossy, normal drooling, highly acidic
Dull, excessive drooling, mildly acidic
Glossy, normal drooling, mildly acidic
Dull, excessive drooling, highly acidic
a)Which progeny are the nonrecombinants?
b)Which progeny are the double crossovers? What is the gene order?
c)In the Table, assign genotypes to each of the phenotypes using linkage notation.
d)Calculate the recombination frequencies and draw the genetic map showing the correct gene order and distances between genes.
Calculate the coefficient of coincidence.
Calculate the interference value.
Observed Number
Glossy, excessive drooling, highly acidic
43
Dull, normal drooling, mildly acidic
36Glossy, excessive drooling, mildly acidic
13Dull, normal drooling, highly acidic
4Glossy, normal drooling, highly acidic
333Dull, excessive drooling, mildly acidic
303Glossy, normal drooling, mildly acidic
130Dull, excessive drooling, highly acidic
138 1000Explanation / Answer
Answer:
Phenotypes
Short hand genotypes
Observed Number
Glossy, excessive drooling, highly acidic
GDA
43
Dull, normal drooling, mildly acidic
gda
36
Glossy, excessive drooling, mildly acidic
GDa
13
Dull, normal drooling, highly acidic
gdA
4
Glossy, normal drooling, highly acidic
GdA
333
Dull, excessive drooling, mildly acidic
gDa
303
Glossy, normal drooling, mildly acidic
Gda
130
Dull, excessive drooling, highly acidic
gDA
138
1000
Imaginary order is GdA/gDa
1. If single cross over (SCO) occurs between G & D
Normal order= G---------d & g-----D
After cross over= G-----D & g------d
G-----D recombinants are 43 + 13 = 56
g------d recombinants are 36+ 4 = 30
Total recombinants = 86
RF = (86/1000.)*100 =8.6%
2. If single cross over (SCO) occurs between d & A
Normal order= d---------A & D----a
After cross over= d-----a & D------A
d-----a recombinants are 130+36 = 166
D------A recombinants are 138+43 = 181
Total recombinants = 347
RF = (347/1000)*100 = 34.7%
3. If single cross over (SCO) occurs between G & A
Normal order= G---------A & g------a
After cross over= G-----a & g------A
G-----a recombinants are 13+ 130 = 143
g------A recombinants are 4+ 138= 142
Total recombinants = 285
RF = (285/1000)*100 =28.5%
% RF = Map unit distance
The order of genes is -----
d---8.6 m.u.---G-------28.5 m.u.--------A
a). Non recombinant progeny are
Glossy, normal drooling, highly acidic & Dull, excessive drooling, mildly acidic
b). The double crossover progeny are
Glossy, excessive drooling, mildly acidic & Dull, normal drooling, highly acidic
The gene order is d---8.6 m.u.---G-------28.5 m.u.--------A
dGA/Dga (normal)
After double crossover, the order is dgA/DGa
d).
RF between d & G = 8.6% = 0.086
RF between G & A = 28.5% = 0.285
RF between d & A = 34.7% = 0.347
RF = distance between the genes
The gene order is d---8.6 m.u.---G-------28.5 m.u.--------A
Expected double cross overs = 0.086 * 0.285 = 0.025
Observed double cross overs = 0.013 + 0.004= 0.017
Coefficent of coincidence (COC) = Obeserved dco / Expected dco
COC = 0.017/0.025 = 0.68
Interference = 1-CC = 1-0.68 = 0.32
Phenotypes
Short hand genotypes
Observed Number
Glossy, excessive drooling, highly acidic
GDA
43
Dull, normal drooling, mildly acidic
gda
36
Glossy, excessive drooling, mildly acidic
GDa
13
Dull, normal drooling, highly acidic
gdA
4
Glossy, normal drooling, highly acidic
GdA
333
Dull, excessive drooling, mildly acidic
gDa
303
Glossy, normal drooling, mildly acidic
Gda
130
Dull, excessive drooling, highly acidic
gDA
138
1000
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