Eye Colour in Drosophila - Experiment 2

Question 1

What are the two pigment pathways that lead to the brick red eye colour in Drosophila?

Answer 1

Ommochrome and Pteridine

Question 2

What are the possible eye colours for Drosophila?

Answer 2

Brick-red, scarlet, white, apricot, brown, sepia

Question 3

What are the two precursors for the pigment pathways?

Answer 3

Tryptophan is the precursor for the ommochrome pathway, GTP is the precursor for the pteridine pathway

Question 4

What sort of mutation and where in the pathways would be mutated to produce the white phenotype?

Answer 4

A null mutation that knocks out both pathways, likely a transport protein

Question 5

What sort of mutation and where in the pathways would be mutated to produce the sepia phenotype?

Answer 5

A null mutation that knocks out most of the pteridine pathway

Question 6

What sort of mutation and where in the pathways would be mutated to produce the brown phenotype?

Answer 6

A null mutation that knocks out all the pteridine pigments

Question 7

What sort of mutation and where in the pathways would be mutated to produce the scarlet phenotype?

Answer 7

A null mutation early in the ommochrome pathway that knocks out the entire pathway

Question 8

What sort of mutation and where in the pathways would be mutated to produce the apricot phenotype?

Answer 8

A hypomorphic allele in the same gene that produces the white phenotype. Results in partial function of both pathways

Question 9

What is the difference between a null allele and a hypomorphic allele?

Answer 9

A null allele completely knocks out the function of a protein, while a hypomorph still retains partial function

Question 10

Why can’t flies have blue eyes when blue is observed on the chromatogram?

Answer 10

The pigments that show up as blue on the chromatogram are only visible under UV light, they can’t be seen under visible light