Reference no: EM131406

1. The genes for ruby eyes (rb), tan body (t) and cut wings (ct) are all found on the X-chromosome of Drosophila melanogaster. All of these are recessive traits. They map in the order rb, ct, t with 12.5 map units between rb and ct and 7.5 map units between ct and t. Suppose you cross a cut wing male with a homozygous female that is both tan and has ruby eyes.

a. What will the F1 females look like?

b. Draw map of the section of the  X chromosomes that has these 3 genes for the F1 females

c. Assume you testcross your F1 females.

                  i.   What progeny classes would you expect?

                ii.   Give approximate numbers for each class based on a total of 2000 progeny.

                                1. Assuming the i=1 and there are no double crossovers.

                                2. Assuming the i=0 and there are the expected number of double crossovers.

2.      The Neurospora  cross was made between a strain that carried mating type A and the mutant allele arg-1(arg) and another strain the carried mating-type a and the wild type arg-1  (+)gene. Four hundred linear octads were isolated and they fell into the 7 categories given in the table below.

a.       Label each class and PD, NPD or TT

b.      Are the genes linked?

c.       What are the map distance between these genes and the centromere?

 

Class 1	Class 2	Class 3	Class 4	Class 5	Class 6	Class 7
A arg	A +	A arg	A arg	A arg	A +	A +
A arg	A +	A +	a arg	a +	a arg	a arg
a +	a arg	a arg	A +	A arg	A +	A arg
a +	a arg	a +	a +	a +	a arg	a +
127	125	100	36	2	4	6

3.      Assume you are analyzing the information from 4 generations of a human family that has an autosomal recessive disorder. You have an RFLP band that is linked to the gene for the disorder. The recombination frequency between the gene and the RFLP is 20%. The data from this family is presented in a table below.

a.       What is the probability II1 is a carrier?

b.      What is the probability III4 is a carrier?

c.       IV2 has not been born yet but amniocentesis has given the banding pattern shown. What is the probability he will have the disorder?

Individual	Disorder status	RFLP pattern
I1	affected	A
I2	unaffected	B
II1	unaffected	A/B
II2 (unrelated spouse of II1)	unaffected	A/B
III1 (unrelated spouse of III2)	unaffected	A/B
III2	unaffected	A/B
III3	affected	A
III4	unaffected	B
III5	affected	A
III6	unaffected	B
IV1 (child of III1 and III2)	?	A

4.      You have four lines of mice that are homozygous at two linked  loci. One line has a waltzing gait (W W) and a bent tail (BB)  another has normal gait (ww) and a straight tail (bb); the third waltzing gait(WW) and straight tails(bb) and the forth has normal gait (ww) and bent tails (BB). W is dominate to w and B is dominate to b. You cross the pairs of mice and produce an F1 generation. Then you mate the sibs from the F1 generation to each other. What is the chromosomal complement for each of the mice a-c in the table?

Parental mice		F2 phenotypes
	WB	Wb	wB	wb
A	0	103	0	34
B	93	0	29	0
C	52	21	18	5

5. Drossophila females of normal appearance but heterozygous for three autosomal genes are mated to males that are homozygous recessive for the three genes: glassy eyes, coal-color bodies and striped thoraxes. 1000 progeny from this cross are scored

Trait	number
Wild type	35
Striped thorax	4
Coal body	456
Glassy eyes and Coal body	5
Glassy eyes and striped thorax	476
Glassy eyes, striped thorax and coal body	29

a. Draw the genetic map based on these data

b. Show the arrangement of the genes on the two homologs in the heterozygous female including the distance between the genes in cM.

c. Based on your map what is the expected number of double cross overs?