L8 Mutant Analysis of Drosophila Development

Question 1

Point mutations

Answer 1

A point mutation is a mutation that only affects a single nucleotide of nucleic acid. Point mutations most commonly involve the substitution of one base for another (which changes the complementary base as well in DNA).

Question 2

Deletion

Answer 2

a part of a chromosome or a sequence of DNA is lost during DNA replication

can be small or large

Question 3

P-elements

Answer 3

P elements are transposable elements that were discovered in Drosophila as the causative agents of genetic traits called hybrid dysgenesis. The transposon is responsible for P trait of P element and it is found only in wild flies.

• have a bias to where it jumps into

Question 4

piggyBAC

Answer 4

The PiggyBac (PB) transposon is a mobile genetic element that efficiently transposes between vectors and chromosomes via a “cut and paste” mechanism.

• unbiased

Question 5

Minos/MiMIC

Answer 5

Minos mediated integration cassette (MiMIC), in Drosophila melanogaster. MiMIC contains a gene-trap cassette and the yellow+ marker flanked by two inverted bacteriophage ΦC31 attP sites

Question 6

RNAi

Answer 6

RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules

Question 7

Chromosomal balancers

Answer 7

They are used to maintain deleterious mutations in stable stocks as well as to prevent recombination and follow chromosomes in genetic mating schemes.

1. WT for all genes so you can keep your lethal allele in a heterozygous state (gene-/+)
2. multiple rearrangements to prevent meiotic recombination
3. carry dominant markers (so you know they’re present)
4. homozygous lethal or sterile (so they don’t take over the stock)

Question 8

Transposon insertions

Answer 8

transposons carrying cargo-DNA constructs injected into embryo expressing transposase can jump into a gene and disrupt normal expression

Question 9

Site specific recombinases

Answer 9

enzymes that catalyze the recombination of two DNA molecules with two target site sequences (which may be the same or different)

1. FLP/FRT
2. theta-C31/attP-attB

Question 10

FLP/FRT system

Answer 10

• the two target sequences are the same

- by positioning two FRT sites in particular orientations, different effects can be achieved

Question 11

theta-C31/attP-attB

Answer 11

• the two target sequences; attP and attB are different

- resultant spliced sequences (attL and attR) not the same as the original attP and attB

Question 12

Repressible cell marker

Answer 12

• GAL4 repressor, GAL80

- if the repressor is lost, results in positively marked cell

Question 13

Recombination Mediated Cassette Exchange

Answer 13

MiMIC cassette has two attP sites

• so the MiMIC cassette can be swapped with any cassette that has two attB (if theta-C31 is present)
• this means one MiMIC line can be converted to many different constructs

Question 14

Transheteroallelic genotypes

Answer 14

see onenote

Homozygous for other loci as well, how can we be sure that the other mutations isn’t causing the lack of beta-gal

using different alleles mean background mutations can complement each other