G10-11 Flashcards
What is forward genetics
phenotype -> gene
asks what genes are involved in a bioligical process
what is reverse genetics
gene -> phenotype
ask what biological processes a gene is involved in
what does the chemical mutagen EMS do?
adds ethyl group to O-6 position of Guanine (alkylation)
Et-G now pairs with T. G:C to A:T transition
what are the possible outcomes of EMS mutagenesis
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
what are forward genetic screenings easier in?
hermaphrodites
What are the 6 mutation types
null hypomorph haploinsufficient neaomorphic hypermorphic antimorphic
what is a hypomorphic mutation
partial loss of gene function, reduced level of activity, wild type expressed at a reduced level
what is a haploinsufficient mutation
diploid organism has only single functional copy not enough gene product produced to bring about wildtype
what is a neaomorphic mutation
change in gene leads to atypically new function of gene
what is a hypermorphic mutation
gain of cuntion, increase in an otherwise normal gene function
what is an antimorphic mutation
antagonizes normal gene function.
how can you work out if mutation is true null? why might it not be
could be hypomutation etc
genetic analysis required
what are the steps after mutagenesis
outcross to see if breeds true
determine mutation type
complementation tests
mapping
what bias is shown if mutation is linked to a marker?
bias towards mutant parent band
what is a modifer screen?
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.
what kind of insect is drosophilia melanogaster?
a homolemetabolous insect, - complete metamorphism egg-> larva to pupa to fly
why is drosophilia melanogaster a good model organism
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.
give two examples of homeotic mutants
bithorax where T3 segment is replaced bya second T2
antennapedia - antennae into legs.
what is intragenic complementation
when mutations in the same gene complement - eg. multifunctional proteins.
what is extragenic non complementation
non allelic non complementation mutations in two different genes fail to complement - eg. subunit of same protein complex.
what did mice mutaants targeted for knockout of HoxC8 gene reveal?
rib duplication and clenched finger phenotype
what do homeotic genes code for?
a class of transcirption factors called homeodomain proteins.
