Fruit fly mutants: and introduction to Drosophila genetics

                Fruit flies have been used as a model system to study Genetics for more than a hundred years. In the lab we use dissection microscopes to observe Drosophila mutants, but if you do not have one you can use a USB microscope attached to a laptop to take a look at them:

 

                Here is a brief description of some of the mutants that we use in our classroom experiments. You can perform the indicated crosses to demonstrate basic Genetics concepts (i.e. recessive vs dominant alleles, autosomal vs sex-chromosome linked inheritance, etc.).

 - ebony (e)  – is a gene that suppresses melanin formation (mutants in the ebony gene make too much melanin, so their cuticle is dar

 

 

 

ebony is a recessive mutation in the third chromosome.

  • If you cross ebony flies with wild type ones the progeny would be all wild type.

- Curly (Cy)is a gene required for the formation of the fly wing (mutants in the Curly gene have their wings “curled” upwards).

  • Curly is a dominant mutation in the second chromosome.

  • It is lethal in homozygosis, so flies with Curly wing phenotype carry one copy of the mutation Cy in one chromosome and one copy of wild type gene in the other chromosome

  • If you cross Curly flies with wild type 50% of the progeny would be Curly and 25% wild type.

- white (w) – is a gene required for the pigmentation of the fly eye (mutants in the white gene lack eye pigments and therefore have white eyes; these flies are blind!).

  •                white was the first mutant ever discovered in flies.

  •                white is a recessive mutation in the X chromosome, so it is an                 example of sex-linked inheritance.

  •                Drosophila males (like humans) are XY, only have one X           chromosome; females are XX.

  •                If you cross white male flies with wild type females all the progeny would be red eyed (wild-type).

  •                If you cross white female flies with wild type males all the males would be white- eyed and all the females would be red eyed (wild-type).