Lab Quiz 2

Question 1

Two Distinct Protein pigments pathways

Answer 1

Pteridine pathway
Ommochrome pathway

Question 2

If both are blocked

Answer 2

No pigments are produced: white (w)

Question 3

If a fly shows the wild-type phenotype

Answer 3

Pteridine (bright red) and ommochrome (brown) are present.
Both pathways are functional (st+//st+; bw+//bw+)

Question 4

If a fly shows the scarlet phenotype

Answer 4

Ommochrome (brown) pigment is not present (only bright red)
The scarlet gene regulates the ommochrome pathway (st//st)

Question 5

If a fly shows the brown phenotype

Answer 5

No pteridine (bright red) pigments are present.
The brown gene regulates the pteridine pathway (bw//bw)

Question 6

For these flies to show wild-type, scarlet or brown

Answer 6

They must have at least one copy of the “wild” white allele (w+)

Question 7

If the brown and scarlet genes are both mutated (bw//bw; st//st)

Answer 7

No pigments will be produced.
The fly will be white.
It does not matter if they have a normal white allele (w+)

Question 8

If a fly has no normal w+ allele (i.e w//w females or w/y for males)

Answer 8

Both pathways are blocked. No pigments are produced.
The fly will be white.
w is epistatice over st and bw.

Question 9

Dihybrid cross

Answer 9

AaBb x AaBb