Question

In early 20^th century, the inheritance pattern of two fly mutants (eye color, w⁺ or w; body color, y⁺ or y) was used for discovering genetic linkage and crossing-over. Answer the following questions.

P          w⁺,y⁺/w⁺,y⁺                  x          w,y/Y

F1        w⁺,y⁺/w,y                    x          w⁺y⁺/Y

F2        w⁺,y⁺/Y    (Category 1)

            w,y/Y       (Category 2)

            w⁺,y/Y     (Category 3)

            w,y⁺/Y     (Category 4)

6. Let’s assume you used the following breeding scheme at the P stage and repeated the entire experiments. Which is INCORRECT regarding this set of results?

P          w,y/w,y                       x          w⁺,y⁺/Y

1. All of the F1 females should be normal with red eye and brown body.
2. All of the F1 males should be mutant with white eye and yellow body.
3. The mapping distance between two genes should be same as the original breeding scheme, thus the number of male F2 progeny for each category should be similar.
4. All of the above
5. None of the above

Answer 1

Answer: Option E is correct
Explanation:
Parental cross: wy/wy X w+y+/Y
F1 progeny: w+y+/wy wy/Y
F1 selfing: w+y+/wy X wy/Y
F2 progeny:
w+y+/wy = Carrier female
w+y+/Y = WT male
wy/wy = Affected female
wy/Y = Affected male

All the F1 females are normal with red-eye and brown body = True
All the F1 males are mutant with a white eye and yellow body = True
The mapping distance will not change with the type of the cross as the set of genes are the same in either case.