drosophila/ compensation Flashcards
What are the advantages of using drosophila?
Simple and cheap breeding, short life cycle, high number of offspring, polytene chromosomes
Describe the life cycle of drosophila
egg - 3 larval instars - pupa (6-8 days)
imago (2hrs) - adult (4-6 days)
14 total days at room temp
10 total days at 25 degrees Celsius
How are males different from females?
Female is generally larger, has small pointed genital area at abdomen, while male has rounder dark area.
Males have sex combs
What are the functions are pterdine and ommachrome
pterdine makes red pigment, ommachrome makes brown pigment, when both pathways work, brick red wild type eyes are shown
knocking out both creates white eyes
Describe bw/bw, cn/cn, and v/v
bw/bw flies have brown eyes, flies with cn/cn or v/v don’t make ommachrome but do make pterdine, causing red eye color, both are the same phenotypically.
If bw/bw and either of the others are present, flies will have white eyes.
Why do all flies in the experiment have bw/bw?
So that a change in eye color via manipulations can be easily seen.
What is complementation?
When the effects of two different nonallelic mutations in a gene are partly or entirely canceled out when they occur together by crossing strains carrying the mutations
What happens when cinnabar and vermillion are crossed?
If they are on the same gene, F1 (cn/v bw/bw) will be heterozygous but will still show white eyes since cn and v are both defective in making E1.
If they are on different genes, F1 will have a working copy of each gene required to make E1/E2, so it will show the wildtype.
What were the results of the experiment?
Brown eyes in progeny, therefore cn and v are mutated in different enzymes in the ommachrome pathway.
What will happen in the compensation experiment?
kynurenine, an intermediate of enzyme 3 in the ommachrome pathway will be added.
If the mutation is corrected ( brown pigment is made), then we can assume the mutation occurred in the first two enzymes, if the mutation isn’t corrected, we can assume it occurs after enzyme 3.
