To determine:
The order of the genes and the distance between genotypes on the basis of two point crosses.
Introduction:
A series of mutations affects the biosynthetic pathway leading to tryptophan in the bacterium Bacillus subtilis. The seven strains are studied along with their mutation.
Explanation of Solution
The two points cross between the genotypes is as follow:
Recipient | Donor | Cross | Genotypes | The percent of recombination. |
T3 | 168PT | T-I- | 12.7 | |
T3 | TII | T-I- | 11.8 | |
T3 | T8 | T-A- | 43.5 | |
T3 | H25 | T-H- | 28.6 | |
168 | H25 | I-H- | 44.9 | |
TII | H25 | I-H- | 41.4 | |
TI | H25 | I-H- | 31.3 | |
T8 | H25 | A-H- | 67.4 | |
H25 | T3 | H-T- | 19.0 | |
H25 | T11 | H-I- | 26.3 | |
H25 | T1 | H-I- | 13.4 | |
H25 | T8 | A-H- | 45.0 |
The average of observed recombination is found by:
The sums of observations need to be taken as
(a)
(b)
(c)
(d)
(e)
The distance between the genes is as follows:
Gene pair | Distance |
A and H | 56.2 m.u. |
T and A | 43.5 m.u |
I and H | 31.5 m.u. |
T and H | 23.8 m.u. |
T and I | 12.3 m.u. |
To draw:
A map of the genes on the chromosome.
Introduction:
A series of transformation is carried out on strains having the different mutations. The percentage of recombinants is determined by the crosses between the recipient and the donor.
Explanation of Solution
The genetic map drawn based on the genetic distance is as follow:
The distance between A and I is determined as:
Distance between A and I = (Distance between A and T)-(Distance between I and T)
Distance between A and I = (43.5-12.3) m.u
Distance between A and I = 31.2 m.u
The distance between the genes is determined by the crosses in between the genotypes.
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Chapter 9 Solutions
Genetics: A Conceptual Approach 6E w/ SaplingPlus (Six-Month Access)
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