G10-11

Question 1

What is forward genetics

Answer 1

phenotype -> gene

asks what genes are involved in a bioligical process

Question 2

what is reverse genetics

Answer 2

gene -> phenotype

ask what biological processes a gene is involved in

Question 3

what does the chemical mutagen EMS do?

Answer 3

adds ethyl group to O-6 position of Guanine (alkylation)

Et-G now pairs with T. G:C to A:T transition

Question 4

what are the possible outcomes of EMS mutagenesis

Answer 4

mispairing not detected: DNA replication fixes the mutation GC to AT transition
repair by de-ethylation O-6 alkylguanine DNA transferase
Repair by base excision: could lead to transversion, frameshift, DSB etc

Question 5

what are forward genetic screenings easier in?

Answer 5

hermaphrodites

Question 6

What are the 6 mutation types

Answer 6

null
hypomorph
haploinsufficient
neaomorphic
hypermorphic
antimorphic

Question 7

what is a hypomorphic mutation

Answer 7

partial loss of gene function, reduced level of activity, wild type expressed at a reduced level

Question 8

what is a haploinsufficient mutation

Answer 8

diploid organism has only single functional copy not enough gene product produced to bring about wildtype

Question 9

what is a neaomorphic mutation

Answer 9

change in gene leads to atypically new function of gene

Question 10

what is a hypermorphic mutation

Answer 10

gain of cuntion, increase in an otherwise normal gene function

Question 11

what is an antimorphic mutation

Answer 11

antagonizes normal gene function.

Question 12

how can you work out if mutation is true null? why might it not be

Answer 12

could be hypomutation etc

genetic analysis required

Question 13

what are the steps after mutagenesis

Answer 13

outcross to see if breeds true
determine mutation type
complementation tests
mapping

Question 14

what bias is shown if mutation is linked to a marker?

Answer 14

bias towards mutant parent band

Question 15

what is a modifer screen?

Answer 15

when a an organism with a pre-existing phenotype is selected, thus any mutations caused by mutagen (EMU) can be assessed for their enhancive to suppressive activity.

Question 16

what kind of insect is drosophilia melanogaster?

Answer 16

a homolemetabolous insect, - complete metamorphism egg-> larva to pupa to fly

Question 17

why is drosophilia melanogaster a good model organism

Answer 17

50% of fly genes have vertebrate homologs, small and easy to grow in the lab with a short life cycle and high amount of offspring.

Question 18

give two examples of homeotic mutants

Answer 18

bithorax where T3 segment is replaced bya second T2

antennapedia - antennae into legs.

Question 19

what is intragenic complementation

Answer 19

when mutations in the same gene complement - eg. multifunctional proteins.

Question 20

what is extragenic non complementation

Answer 20

non allelic non complementation mutations in two different genes fail to complement - eg. subunit of same protein complex.

Question 21

what did mice mutaants targeted for knockout of HoxC8 gene reveal?

Answer 21

rib duplication and clenched finger phenotype

Question 22

what do homeotic genes code for?

Answer 22

a class of transcirption factors called homeodomain proteins.