Drosophila F1 cross

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Drosophila F1 cross

• Feb. 20-23, 2007

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Grab your fly vials

• Two main tasks
• Score phenotypes for F1 generation
• anesthetize flies, separate males/females
• score traits for both sexes separately first
• if different between males and females, trait may
  be sex-linked if not, autosomal
• Start F1 cross
• take 3 males, 3 females from each culture and
  place them into a new vial.
• please be sure to label your vial with your name
  and section number!

3
Predicting inheritance

• If your mutation is autosomal
• From your F1 generation, you should have an idea
  of whether your mutations are dominant or
  recessive

if mutation is recessive
if mutation is dominant
all offspring are wild-type
all offspring are mutant
4
Predicting inheritance

• If your mutation is sex-linked

if mutation is sex-linked recessive
if mutation is sex-linked dominant
all females wild-type all males mutant
all females mutant all males mutant
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Why do an F1 cross?

• Are your mutations on the same or different
  chromosomes?
• If on different chromosomes, they will sort
  independently
• 9331 ratio
• If on same chromosome, the mutant traits should
  show up together most of the time
• will NOT conform to a 9331 ratio

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How to predict your F2 generation
If both sepia and dumpy are dominant and
autosomal
9 sepia, dumpy
3 sepia, normal
3 normal, dumpy
1 wild-type