Suppose there are three new eye colour mutants in Drosophila, called mutant A, m

Question

Suppose there are three new eye colour mutants in Drosophila, called mutant A, mutant B and mutant C. To find out if these new mutant alleles are in a gene already known to be involved in eye colour, crosses for complementation tests were performed: the new mutants were crossed to null mutants in four different genes already known to control eye colour: rosy, brown, cinnabar and scarlet. The results are shown in the table. Explain what the complementation results indicate about each of the three new mutants: mutant A, mutant B and mutant C. '+' indicates progeny had wildtype eye phenotype '-' indicates progeny had mutant eye phenotype

Explanation / Answer

A complementation test (sometimes called a "cis-trans" test) can be used to test whether the mutations in two strains are in different genes. Complementation will not occur if the mutations are in the same gene.

1. Mutant A when cross with muatnt A & C (-) signify mutations in two strains are in different genes while with mutant B (+) mutations are in the same gene.

2. Muatnt B when crossed with Muatnt A (+) signify mutations are in the same gene.while with B & C (-) signify mutations in two strains are in different genes.

3. Mutant C when crossed with A, B & C (-) signify mutations in two strains are in different genes.

4. wild type when crossed with Muatnt A & B (+)  signify mutations are in the same gene while with Mutant C (-) signify mutations in two strains are in different genes.

5. rosy null when crossed with mutant A & C(-) signify mutations in two strains are in different genes. while with mutant B (+) signify mutations are in the same gene.

6. brown null when crossed with A & B (+) signify mutations are in the same gene while with mutant C (-) signify mutations in two strains are in different genes.

7. cinnabar null when cross with mutant A (+) signify mutations are in the same gene while with mutant B & C (-) signify mutations in two strains are in different genes.

8. scarlet null when crossed with mutant A & B (+) signify mutations are in the same gene while mutant C (-) signify mutations in two strains are in different genes.

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