Our Test OrganismDrosophila simulans

Trait of Interest

• Red vs. White• Red = advantageous “mutation”• Why are red eyes advantageous?

• Sensory perception• White eyes = reduced mate tracking

Drosophila chromosome

Red / Whiteeye color gene

“Near” “Far”

22 million bases of DNA

What are we going to look at?• Two markers on X-chromosome

o One close to the gene for white eyeso One far from the gene for white eyes

• Why are we going to look at 2 markers?

22 million bases of DNA

Microsatellites & Genetic Markers• Sequence differences (aka variation) between

alleles• Usually base pair repeats, insertions, or

deletions• Used for between & within-species

comparisons

Selective Sweep/HitchhikingBefore sweep After sweep

This is one chromosome from 12 different people. The different colors represent different alleles for that gene.

What happened?

How are we going to observe & measure genetic variation?

Step 3: Introduce “advantageous mutation”

Allow mating for several generations

Anesthetizing fliesFlyNap – Stinky!

Red male

Red female

White male

White female

Sexing your flies: males have a “black butt”, females have large white abdomen

How to tell males from females

• Males have black abdomens

• Look close at the tip of the male abdomen and you will see his junk

• Females have rounded abdomens

Female Male

Sexing

Female Male

Our Treatments

• Control group:– 5 white-eyed males, 5 white females

• Experimental group:– 5 white-eyed males, 5 white females, 1 red male(“mutant”)

Started with this…

Control group:5 white-eyed males, 5 white

females

Experimental group:5 white-eyed males, 5 white

females, 1 red male

Red eyed males Red eyed females

White eyed males White eyed females

Sort into categories and count

After 1 Generation, you will sort the fliesOn a white piece of paper….