Population Genetics Flashcards
What is the study of population genetics?
The study of variation in allele and genotype frequencies within a population
What does it mean is genes are polymorphic?
they will occur in a number of different forms/ alleles - multiple versions of them exist (i.e: hair colour, eye colour)
What is the gene pool
the collection of all the alleles of all the genes found within a freely interbreeding population
Why does Hardy-Weinberg Equilibrium rarely apply to population genetics?
Because it is a null model. It can only be applied if the following are NOT active:
- Mutations
- Sexual selection
- Genetic drift/ gene flow
What is recombination?
the process whereby a cell generates new chromosomal combinations, compared with that cell or with those of its progenitors
Does recombination create new diversity?
No - it generates new combinations of existing diversity, creating more VARIATION
What letter represents the effective population?
Ne
What does ‘Ne’ describe?
The effective population size - shows the same rate of loss of genetic variation due to genetic drift as for the population of interest
Name 3 consequences of a decreasing population size?
Inbreeding
Genetic drift
Homozygosity
Subpopulation differentiation
Why is Ne generally less than N?
population sizes vary from generation to generation
Unequal sex ratios
Overlapping generations
Geographical dispersion of populations
What is gene flow
the introduction of genetic material (by interbreeding) from one population of a species to another, thereby changing the composition of the gene pool of the receiving population
Why is gene flow good for populations?
The introduction of new alleles through gene flow increases variability within the population and makes possible new combinations of traits
What are two ways for gene flow?
Immigration
Emigration
Which letter represents the movement of individuals
f
What is genetic drift?
the change in the frequency of an existing gene variant (allele) in a population due to random sampling of organisms
- as a results of random fluctuations in the transfer of alleles from one generation to the next
What is the difference between genetic drift and gene flow?
Genetic drift = changes in gene frequencies from one generation to the next
Gene flow = variation in gene frequencies from one population to another
Which two effects can cause genetic drift?
Bottle necking
Founder effect
What is the bottle neck effect
When adverse environmental conditions reduce the genetic variation in a population
What is the founder effect?
The loss of genetic variation due to geographical separation of a subset of the population
Give an example of bottle necking
Northern Elephant Seals in the 1890s - hunting reduced population size and subsequently genetic variation
What are mutations
changes in the DNA sequence caused by the insertion, deletion or point mutation
what is inbreeding and outbreeding
Inbreeding = mating with relatives - causes homozygosity
Outbreeding = mating with non-relatives - increases heterozygosity
how do you calculate the inbreeding coefficient
F = (expected no. heterozygotes under random mating - actual freq. of heterozygotes) / expected no. heterozygotes
what are darwin’s 3 basic conclusions
Organisms produced more offspring than can survive
Living things are locked in a struggle for survival
Individuals of the same species are rarely identical (they show variation)
Name 3 examples of behavioural adaptations
Mating calls
Co-operative hunting
Tool use
Name 3 examples of physical (structural) adaptations
Talons Beaks Fur Colouration (camouflage) Long necks in giraffes
Name 3 examples of physiological adaptations
Fat storage in camel humps
Venom/ poison
Hibernation
Metabolic changes
name 2 modern examples of natural selection
- Use of antibiotics are leading to resistant bacteria – ‘superbugs’
- Rats have a modified enzyme that allows blood to clot even in the presence of Warfarin
define selection pressure
the severity of an organisms circumstances on survival
if the selection pressure is greater, what happens to the rate of evolution?
it increases
what are the 3 types of selection
stabilising
disruptive
directional
which is the most common type of selection
directional
describe directional selection
When organisms with a particular phenotype have an advantage and survive to reproduce
Describe stabilising selection
in a favourable/unchanging environment selection can lead to standardisation of organisms by selecting against extremes
Describe disruptive selection
Where only organisms with extreme phenotypes are selected - phenotypes selected AWAY from the norm
What is speciation
The formation of a new species
when does speciation occur?
When parts of populations get isolated, experience different environmental conditions
