sex and recombination Flashcards
what is the effect of sex recombination
does not change allele frequency
breaks down association between alleles, reduces “linkage disequilibrium”
can increase or decrease genetic variation
brings new sets of genes together
how does the benefit of asexuality affected by time
asexuality may be advantageous in the short term however it is not beneficial over a long time (in animals)
there is advantage since asexual female produces twice as many females so increasing baby making power since females make de babies
sex overcomes mullers ratchet; since class with no/ very few mutations is very small the chance of it becoming extinct due to them not reproducing is high, and so is likely to die out, and the next class and so on, in asexual populations this class may not be regained, however this may occur in sexual populations since not all mutations are necessarily passed on, sex speeds up adaptation since mutations can be combined, in asexual they may only be combined if an already mutated organism undergoes another mutation (applies to beneficial mutations)
describe the breeding of the amazon molly
formed by hybridisation of P.mexicana and P.latipinna; is a parthenogenetic species, does not undergo meiosis, there is a diploid egg, requires sperm to trigger development however sperm genome is ejected, genetic evidence suggests over 100,000 years old however this may be explained by large population size and so the ratchet is slowed
what is linkage disequilibrium
the non random association of alleles, the closer genes are to eachother loci wise the more likely they are to be linked
what makes genetic extremes rare
negative epistasis, since a large number of mutations is likely to include deleterious mutations
a study comparing multiple mutations in a single gene U3 snoRNA showed that a model with epistasis predicted fitness better than the model without, weird coz yeast are asexual and so do not undergo epistasis
how does C.elegans worm breeding vary in different environments
they are either self reproducing hermaphrodites or can mate with males produced by starving other males,
in control environment there is little male reproduction, in an environment with a fixed strain of pathogen there is an initial increase in male production to allow for initial adaptations followed by a reduction to normal levels, in an environment with a co-evolving (non fixed strain) of pathogen male production persists at a higher rate
how is sex adaptation studied in yeast
a study compared a population that reproduced asexually and another where sex occurred every 90 generations, the asexual population had many more mutations, and had a similar number of fixed mutations to total mutations, sexual group had fewer mutations, but also a much smaller amount of fixed mutations than total
