In the fruit fly, Dichaete (D) is a dominant autosomal mutation that affects win
ID: 204414 • Letter: I
Question
In the fruit fly, Dichaete (D) is a dominant autosomal mutation that affects wing shape; it is lethal when homozygous. Ebony body, e, and pink eye, p, are recessive mutations also located on the same chromosome. Dichaete F1 flies from a cross of dichete ebony x pink were test-crossed, and 1000 progeny collected.
A. Diagram these crosses. :
B. Predict the numbers of testcross progeny in each phenotypic class:
__________________________ Dichaete
Pink
Ebony
Dichaete ebony
Ebony pink
Dichaete pink
Dichaete ebony pink
Wild type __________________________
C. Predict phenotypic ratios from test-crosses of each of these three F2 classes: Ebony
Pink
Dichaete ebony pink
Explanation / Answer
Answer:
a).
dichete ebony x pink
Dd ee PP x dd EE pp---Parents
dEp
DeP
DeP / dEp (dichete)
deP
deP / dEp (Wild)
B).
DeP / dEp (dichete) x ddeepp
dep
DEP
DEP / dep (dichete) -1/8
DEp
DEp / dep (dichete, pink) -1/8
DeP
DeP / dep (dichete, ebony) -1/8
Dep
Dep / dep (dichete, ebony, pink) -1/8
dEP
dEP / dep (wild) -1/8
dEp
dEp / dep (pink) -1/8
deP
deP / dep (ebony) -1/8
dep
dep / dep ( ebony, pink) -1/8
Pink = 1/8 * 1000 = 125
Ebony = 1/8 * 1000 = 125
Dichaete ebony = 1/8 * 1000 = 125
Ebony pink= 1/8 * 1000 = 125
Dichaete pink= 1/8 * 1000 = 125
Dichaete ebony pink= 1/8 * 1000 = 125
Wild = 1/8 * 1000 = 125
C).
Ebony = 125
Pink = 125
Dichete ebony pink = 125
The ratio = 1:1:1
dEp
DeP
DeP / dEp (dichete)
deP
deP / dEp (Wild)
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