W6 L3 Drift, inbreeding and population structure Flashcards
Important things to consider about extinction vortex
- Demography
- Reproduction regime
- Ecology
Why is small population a problem
- small population lead to inbreeding and drift, loss of genetic diversity
-reduce in population fitness and adaptivity
-lower reproduction, higher mortality
-low pop, eventually extinction`
Heterozygousity across population
Heterozygousity statistic
What is FST
fixation index measures
- the deficit in heterozygosity within a subpopulation
- the probability of identity by descent of two alleles or inbreeding
- BY EXTENSION, the level of differentiation from the total population is a simple and unique metric describing a range of phenomena
BUT doesn’t allow disentangling the relative contribution of each force.
The effect of population size and drift
The expected effect of population size and drift at a genotypical level
Properties affecting drift:
Inversely proportional to population size
Ultimately, always results in loss of genetic diversity
The probability of fixation of an allele is equal to its frequency.
Isolated population, founding events or demographic fluctuations all aggravate drift.
Change in sex ratio also affects drift.
The definition of inbreeding
Inbreeding designates the mating between relatives, resulting in an inbred individual
The inbreeding coefficient (F) is the probability that the two alleles at a locus in an individual are identical by descent (i.e. descent from a single copy of a recent ancestor).
Why is inbreeding practised
- Create genetic uniformity in laboratory stocks
- Produce homogeneous parents for crossing (F1 hybrids in crops)
Inbreeding at an individual level: coefficient of inbreeding
Apply the general equation to calculate F
At the population level: calculate coefficient of inbreeding
The effect of inbreeding on traits
