Mutation

Human Heredity: Principles and Issues (MindTap Course List)
11th Edition
ISBN:9781305251052
Author:Michael Cummings
Publisher:Michael Cummings
Chapter15: Genomes And Genomics
Section: Chapter Questions
Problem 2QP: Hemophilia and color blindness are both recessive conditions caused by genes on the X chromosome. To...
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You are studying a group of mutations in Drosophila all of which are recessive lethal and map to a  small area of chromosome 3. You decide to perform complementation testing to see which mutations are in the same gene. You have bred your flies such that they have the following genotype:

+; +; TM3 Sb/mut; +

 

This indicates that chromosomes X, 2, and 4 are wild-type. One copy of chromosome 3 is the balancer TM3 Sb which carries a recessive lethal gene and the dominant marker Stubble (Sb), which causes the flies to have short bristles. The other copy  of chromosome 3 carries your recessive lethal mutation.

 

a) Describe how you would maintain each of your individual stocks. What ratios of phenotypes do you expect? 

 

b) When you perform your complementation testing, you will have to look at the F1 phenotypes to determine whether two genes complement. Describe what your F1 fly population should look like if the two mutations complement and if they do not. 

 

You breed each of your four mutations and score complementation. Below are your results (+ indicates complementation, - indicates failure to complement):

 

Mutation

1

2

3

4

1

-

+

-

+

2

+

-

-

+

3

-

-

-

-

4

+

+

-

-

 

c) What is unusual about mutation 3? Provide a possible explanations for this phenomenon. (Hint: remember that all mutations were mapped to a small region of chr3) 

 

d) One way to test your hypothesis in part c is to examine the fly's salivary glands. Describe what this experiment would entail and what flies you would compare. 

 

e) You generate an additional fly line that has two dominant markers, Rosy (Ry)  and Curly (Cy), integrated in the part of chr3 where mutations 1-4 were mapped. Rosy gives the flies ruby red eyes while Curly makes their wings curl backwards. You know that Rosy and Curly are 1 centimorgan (1 map unit) apart. You cross the TM3 Sb/Ry Cy males with TM3 Sb/mut3 females. You retrieve Ry Cy/mut3  females  and cross them to wt/wt males. Describe the phenotypes you would expect for parental and recombinant genotypes (at the three loci you are studying). Then, state why you should not observe any of the recombinant phenotypes in the progeny.  

 

please answer.  a , b , c. 

asap   

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