In tomato, there are 3 genes on the same chromosome. Tall is dominant to dwarf,
ID: 34390 • Letter: I
Question
In tomato, there are 3 genes on the same chromosome. Tall is dominant to dwarf, smooth skin is dominant to peachy skin, and round fruit is dominant to oblate (flattened) fruit. A fully heterozygous individual is crossed with an individual homozygous for all the traits and the phenotypes of the F2 are given in the table below. Using this data, construct a map for these genes, including the distances between them.
Phenotypes
# of individuals
tall, smooth, normal
151
tall, smooth, oblate
33
tall, peach, oblate
11
tall, peach, normal
2
dwarf, peach, oblate
155
dwarf, peach, normal
29
dwarf, smooth, normal
12
dwarf, smooth, oblate
0
Phenotypes
# of individuals
tall, smooth, normal
151
tall, smooth, oblate
33
tall, peach, oblate
11
tall, peach, normal
2
dwarf, peach, oblate
155
dwarf, peach, normal
29
dwarf, smooth, normal
12
dwarf, smooth, oblate
0
Explanation / Answer
Recombinant between tall and smooth
= 11+2+12+0 =25
Recombinant between smooth and normal
= 33+2+ 29+0 = 64
Recombinant between tall and normal
= 33+11+29+12 = 85
Total progeny = 393
Recombinant frequency between tall and smooth = 25/393*100 = 6.36%
Recombinant frequency between smooth and normal = 64/393*100 = 16.28%
Recombinant frequency between tall and normal = 85/393*100 = 21.62%
So map would be
T 6.36 S 16.28 N
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