Genetic Diversity Flashcards
What is genetic diversity?
total number of different alleles in a population
what is a population?
a group of individuals that occupy the same place and can interbreed
what is allele frequency?
how often a particular allele occurs within a population
what is a gene pool?
total number of alleles of a particular population (at a specific time)
what is the advantage of genetic diversity?
the greater the diversity, the greater the number of different alleles that all species possess
- Therefore they are more likely to survive and adapt to environmental change
- they have a wider range of alleles - wider range of characteristivcs
- higher probability that an individual posesses desriable characteristic for new conditions
name five factors that increase genetic diversity
- random mutation
- genetic recombination
- independent assortment
- immigration
- outbreeding
name six factors that decrease genetic diversity
- inbreeding
- reduced gene pool
- small population
- selective breeding
- genetic bottleneck
- founder effect
what is selective breeding?
- humans artificially choosing desirable characteristics and using them as breeding stock
what is the consequence of selective breeding?
- reduced variety of alleles at desired number
- reduced genetic diversity
- unable to adapt to sudden environmental change
how does natural selection work?
- random mutation causes genetic variation
- mutation can either be harmful or beneficial
- individiual with advantageous characteristivs would survive an environmental selection pressure
- survive and reproduce
- pass on beneficial allele to offspring
- over many generations, the frequency of the advantageous allele increases and becomes more common
what are genetic bottlenecks?
- original population contains many different alleles
- sudden population reduction due to natural disaster for example
- only one group has allele which benefits their survival and only they live
- this group reproduces and a population is created of individuals with reduced genetic diversity, since there are fewer different alleles
what are the problems with bottlenecks?
- less variation - as alleles are lost from gene pool
- not representative of original population
- some alleles are overrepresented among population so some may be eliminated completely
give an example of a genetic bottleneck
- northern elephant seal
- over hunting in late 1800s reduced population
- surviving seals repopulated - new population has reduced genetic diversity
name a type of genetic bottleneck
founder effect
what is the founder effect?
- few individuals from a population form a new colony in a new habitat
- since there is a small number of individuals, there is a small number of different alleles in the gene pool
- allele frequency of the new colony is different to allele frequency of original population
- new colony more susceptible to genetic disorder due to lack of new alleles introduced into the population
name an example of a human population who have suffered from founder effect
old order amish population
- colonists escaped persecution to settle in pennsylvania
what is selection?
processs by which organisms that are better adapted to environment survive and breed
name three ways in which an organism may be better suited to the environment
- anatomical
- physiological
- physical
what are polygenes?
characteristics that are influenced by more than one gene`
what are three types of selection
- directional
- stabilizing
- (disruptive)
what is directional selection?
population mean favours one extreme
what is stabilizing selection?
population mean moves towards average
