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Drosophila Genetics

Drosophila Genetics. Drosophila Life Cycle. Four stages Egg Larva Pupa Adult. Sex Determination. Male Smaller Abdomen rounded Tipped with black Female Bigger Abdomen pointed. Culture Vial. Lay your vial on its side . Gently brush all the adult flies of the SIDE WALL of the vial.

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Drosophila Genetics

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  1. Drosophila Genetics

  2. Drosophila Life Cycle • Four stages • Egg • Larva • Pupa • Adult

  3. Sex Determination • Male • Smaller • Abdomen rounded • Tipped with black • Female • Bigger • Abdomen pointed

  4. Culture Vial • Lay your vial on its side. • Gently brush all the adult flies of the SIDE WALL of the vial. • DO NOT SET THE VIAL UPRIGHT! • Count all the flies and determine their phenotype. • Enter the data in the corresponding table of the lab.

  5. Sex Linked Inheritance • In sex-linked inheritance, alleles on sex chromosomes are inherited in predictable patterns. • In Drosophila the locus for eye color is located on the X chromosome. • The allele for red eye color, which is normal in wild flies, is dominant to the mutant allele for white eyes.

  6. Male with White Eye • As females have two chromosomes X (with a locus for eye color), they might be homozygous (XR XR) or heterozygous (XR Xr) for either allele.

  7. Male with Vestigial Wings • Males, who carry only one (XY) chromosome, are always hemizygous. • They carry only the one X chromosome inherited from their mother, and it determines their eye color, so a fly Xr Y will have white eyes, while a XR Y will have red eyes • The same concept applies to vestigial wings

  8. Males and Females

  9. Vestigial (short) and Wild type wings (long)

  10. Genotypes WW – Wild (long wings) Ww – Wild (long wings) ww – vestigial (short wings) - mutation XRXR - Red eyed female XRXr – Red eyed female XrXr - White eyed female XR Y – Red eyed male Xr Y – white eyed male

  11. Mutations • Mutation – sudden genetic change (change in base pair sequence of DNA) which can be passed to future generations. (ie vestigial wings)

  12. WildWings/ White Eyes Short Wings/ Red Eyes WildWings/ Red Eyed Female WwXRXr WildWings/ Red Eyed male WwXRY

  13. WwXRXr WXR WX rwXRwXr WXR WwXRY WY wXR wY

  14. Obtain Chi-Square number

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