gene pool

whats a gene pool

the sum total of all the genes & alleles in a population, at a given time

do gene pools change over time?

yes, they’ll change over time through evolution

• in different environments, there are different niches/habitats to exploit, meaning there’re different selection pressures 

• these changes can lead to natural selection

  • cuz a change in the gene pool means a change in allele frequencies, meaning individuals with advantageous, heritable traits are more likely to survive 

what else do gene pools indicate

indicate genetic variation in a population

• large gene pool indicates extensive genetic variation

  • in turn, indicates the individuals in the population hv a higher ability to adapt to environment, meaning they hv a higher chance of survival '

so - large gene pool = extensive genetic variation = individuals in population hv higher chance of adapting to environment = higher chance of survival

whats allele frequency

the relative frequency of a particular allele (in comparison to other alleles of same gene) in a population

can range from 0 (allele isn’t present at all in population) to 1 (allele is present in all individuals of population)

how do i calculate the allele frequency

can be calculated if you know the genotypes associated with the allele in population

frequency of allele X = # of copies of allele X in population/total # of copies of gene in population

note - there can be more than 2 alleles for a gene

can the frequency of alleles in a population change?

oui it can change due to natural selection & chance, or random events

whats genetic drift?

already kinda mentioned this in A4.1

the change in frequency of an allele in a population, due to random chance events

is the impact of genetic drift greater in large populations? (is there more of an impact on large populations)

no, the impact of genetic drift is greater in small populations & populations that’re geographically isolated from each other

can occur in 2 situations (bottleneck effect & founder effect) - kinda went through this in speciation flashcard set in A4.1

whats the bottleneck effect

the dramatic reduction in population size due to natural disasters

survivors may not represent the genetic diversity of original population

• the population may rebound & grow, but the reduction in genetic diversity means they’re not very adaptable

• is dangerous for diseases - not much difference in allele frequency means not much genetic variation, meaning the whole population may not hv immunity against a specific disease. if the population is affected with the disease, they may not survive 

whats the founder effect?

occurs when a few members of original population establishes a new population

this new population may not be an exact genetic representation of original population (lacks genetic diversity & genetic variation)

as the population increases, composition of gene pool would be different from original population - so, the genotypes & phenotypes would be different (go through this)

just a note - evolution requires that allele frequencies change over time

the allele frequencies in a gene pool would change as a result of natural selection between individuals according to differences in their heritable traits

whats Neo-Darwinism

Darwin stated that natural selection acted on heritable traits, but didn’t rlly explain how exactly heritable traits are passed on to offspring/how heritable traits appear & disappear 

is a theory that’s the result of the combined work of many scientists

the theory tries to explain natural selection on the foundation of Mendelian genetics 

what’re the relevant parts of the theory (check “Gene pools & changes in their composition (HL)” for more info on the theory

• evolution is the change in the genetic composition of the gene pool of a population

• phenotype is largely a product of the genotype

• natural selection increase frequency of useful alleles 

• genetic drift & gene flow can result in changes in gene frequency of a population

• mutations are the ultimate source of genetic variation