You identified another butterfly that is missing just one dot, and establish a p

Question

You identified another butterfly that is missing just one dot, and establish a pure-breeding stock. You decide to call this recessive mutation dotless (dot-).

As the violet gene is clearly working fine in at least some areas of the butterfly, you generate two hypotheses to explain this altered pattern:

1. There is a transcription factor that allows expression of violet in the wing dot, and the transcription factor has a null mutation.

2. There is a cis element (which you identified on page 1) necessary for expression of violet in the upper wing, and this cis regulatory sequence is mutated.

As before, you generate transgenic butterflies by injecting dot-/dot- eggs with two transgenes. Sites making both purple pigment overlapped with lacZ are close to black in color.

Explanation / Answer

1. The hypothesis that colours can be modified with transcription of genes is correct as shown in the data. The white dot genes were made dominant to bring in the black and white dots in the wings of the butterfly.

2. When we cross a dot/dot butterfly to a pur/pur butterfly the offsprings in the F1 generation would be- some purple, some light purple and some totally white with no strains.

Take for example two parent butterfly one purple and the with dots. The F1 generation would have both purple and doted butterfly.However, in the F2 generation, all the offsprings will be purple as it is a dominant colour over white.

We call this gene interaction as epistasis.

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