a.
To determine:
The order of the genes on the chromosome.
Introduction:
Interference is the genetic term that is used in crossover. It is used to measure the degree by which one crossover is interfering with additional crossovers. The coefficient of coincidence is the ratio that is obtained by the division of number of observed double cross over to number of expected double crossover.
Three recessive mutations in Drosophila melanogaster are:
Roughed
Javelin
a.
Explanation of Solution
The following table represents the resulted progeny of cross:
Genotype | Number | Recombinant or non recombinant |
37 | Non-Recombinant | |
2 | Recombinant with single crossover between | |
14 | Recombinant with single crossover between | |
146 | Recombinant with double crossover | |
2 | Recombinant with single crossover between | |
35 | Non-Recombinant | |
154 | Recombinant with double cross over | |
10 | Recombinant with single crossover between | |
Total | 4000 |
Non recombinant and recombinant progeny obtained from single cross over and double crossover can be identified from the resulted progeny.
These are the
These are
On comparing the genotype of progeny non recombinants and recombinants vary at
b.
To determine:
The progeny that will contain single cross over and double crossover with the position.
Introduction:
Interference is the genetic term that is used in crossover. It is used to measure the degree by which one crossover is interfering with additional crossovers. The coefficient of coincidence is the ratio that is obtained by the division of number of observed double cross over to number of expected double crossover.
Three recessive mutations in Drosophila melanogaster are:
Roughed
Javelin
b.
Explanation of Solution
Single crossover occur between the genes
Double cross over will occur between genes
c.
To determine:
The calculation map distances amongst the genes.
Introduction:
Interference is the genetic term that is used in crossover. It is used to measure the degree by which one crossover is interfering with additional crossovers. The coefficient of coincidence is the ratio that is obtained by the division of number of observed double cross over to number of expected double crossover.
Three recessive mutations in Drosophila melanogaster are:
Roughed
Javelin
c.
Explanation of Solution
Distance between the genes can be calculated as:
Distance between the genes
The recombination frequency is calculated by the formula,
The single crossover between
The double crossover between
Substitute the value of the number of recombinant progeny and that of the number of total progeny in equation (1).
The percentage of recombinant frequency is calculated as,
The number of map units in
Therefore, the number of map units in
Hence, the distance between
The distance between the genes
The single crossover between
The double crossover between
Substitute the value of the number of recombinant progeny and that of the number of total progeny in equation (1).
The percentage of recombinant frequency is calculated as,
The number of map units in
Therefore, the number of map units in
Hence, the distance between
d.
To determine:
The calculation of coefficient of coincidence and interference.
Introduction:
Interference is the genetic term that is used in crossover. It is used to measure the degree by which one crossover is interfering with additional crossovers. The coefficient of coincidence is the ratio that is obtained by the division of number of observed double cross over to number of expected double crossover.
Three recessive mutations in Drosophila melanogaster are:
Roughed
Javelin
d.
Explanation of Solution
Expected number of double cross over will be equal to the product of the recombination frequency of single crossover with the sum of total number of progeny.
Recombination frequency of crossover between
Recombination frequency of crossover between
Sum of total progeny =4000
Formula for expected double cross over is,
Formula for coefficient of coincidence is:
Interference is calculated as:
The value coefficient of coincidence = 0.16, and interference =0.8
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Chapter 7 Solutions
Genetics: A Conceptual Approach
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