EB19 Flashcards
What is Mendalian inheritance
all else being equal the gene frequency will not change, two gene copies from mother and father.
fast majority of genes transmitted this way.
What is gene drive
process of preferential inheritance (no longer 50/50)
- lead to spread in population (all else being equal).
what kind of genes usually spread by NS and what can by drive
norally by NS only genes that increase survival of carriers
gene drive can increase spread of deleterious genes = selfish genetic elements.
What are free ways to drive?
killing competition
over replication
directed towards germline
what are 7 examples of killing competition in gene drive
- T-haplotype in mice
- Segregation distorter in Drosophila
- Spore Killer in fungi
- Driving sex chromosome in dipterans
- Feminizing X chromosome in Lemmings
- Cytoplasmic male sterility
- Androgenesis
Describe gene drive of T-haplotype in mice
- two variants T-haplotype and WT.
- T-haplotype 90% inheritance through males
- In heterozygote WT sperm has dysfunctional glagella and or acrosome structure at tend of sperm releasing enzymes preventing penetration and fusion with egg. = most fertilisation by T-haplotype.
- lethal recessive homozygote so only present at 5% in natural populations
what is the T-haplotype
30-40mb on the 17th chromsoome and is inherited as a unit. contains 4 inversions wrt WT preventing recombination between the,
how long has the t-haplotype been present in mice
3 million years resisting selection due to preferential inheritance
Describe Segregation distorter SD in drosophila
- Transitted 95-99% in males
- WT SD heterozygote, WT shows failures in chromatin condensation compared to SD sperm.
* molec mech unknown. - lethal recessive homoxugote SD so present 1-5% in natural populations
Describe spore killer in fungi (ascomycete)
- spore killer heterozygote creates 4 viable containing spore killer and 4 WT inviable spores.
describe spore formation in fungi
haploid hyphae mate to make breif diploid which goes through meiosis to make haploid spores, fruiting bodies associated with mating event.
four meiotic products each of which goes through a single mitotis = 8 products.
Describe driving sex chromsoome in dipterans
- Drosophia: Sperm with Y chromosomes chromatin does not undergo proper condensation and is incapacitated
- Y drive in some mosquito, incapacitates X
* could potentially eliminate population - no known examples.
Describe the feminizing X chromosome in Lemmings
Dominant feminizer causes female development even in presence of Y. X therefore gets 67% transmission.
What organisms can cytoplasmic male sterility be found in
descrbed in >140spp. in 20 families inc. plantago lancelota flowers
Describe cytplasmic male sterility
mitochondrial mutations convert hermaphrodites to females.
- mitochondrial only inherited through ovule not pollen
- pollen production irrelevant to mitocondndiral genes.
- cytoplasmic (mt genes) cause male sterility`