Assume that investigators crossed a strain of flies carrying the dominant eye mu

Question

Assume that investigators crossed a strain of flies carrying the dominant eye mutation Lobe on the second chromosome with a strain homozygous for the second chromosome recessive mutations smooth abdomen and straw body. The F1 Lobe females were then backcrossed with homozygous smooth abdomen, straw body males and the following phenotypes were observed:

smooth abdomen, straw body 820
Lobe 780
smooth abdomen, Lobe 42
straw body 58
smooth abdomen 148
Lobe, straw body 152

(a) Give the gene sequence and the map units between these three loci.
(b) What is the coefficient of coincidence?
(c) What is the interference?

Explanation / Answer

a. The map units and gene order is given as follows:

Smooth abdomen--------- 5------Lobe------15-------Straw body

This means that lobe will be in middle.

b.The coefficient of coincidence will be 0.

c. Interference is given as:

1-  coefficient of coincidence

now putting the value of coefficient of coincidence we get

1-0 = 1 or we can say interference 100%.

This indicates that there won't be any double crossovers.

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