Changes in The Genetic Makeup Of A Population Flashcards
Gene pool
The gene pool is the set of all genes, or genetic information, in any population, usually of a particular species
Mutation
permanent, heritable change in the nucleotide sequence in a gene or a chromosome.
Genome
Aggregation of all genes in a single organism.
Point mutation
Changes to a single base pair.
Block mutation
Entire segments of DNA.
Types of point mutations
- silent mutations
- missense mutations
- nonsense mutations
- frameshift (base addition and deletion)
Duplication
Where segment of DNA is repeated again and again.
Inversion
Where a segment of dna is ‘chopped up’ and reinserted in the same place, but backwards.
Insertion
Where a segment of dna from another molecules is copied and inserted into the middle or another segment of dna.
Block deletion
Segment of dna is removed
Translocation
Where a segment of dna fro one molecule reaches and reinsert itself in another molecule.
Aneuploidy
Aneuploidy is the presence of an abnormal number of chromosomes in a cell.
Polyploidy
Cell contains two or more sets of chromosomes.
Selection pressures
an agent of differential mortality or fertility that tends to make a population change genetically. Selection pressures are the driving mechanism of natural selection.
Artificial selection
Breeder acts as a selection pressure.
Species
Complete set of all organism that are able to mate and produce viable and fertile offspring.
Gene flow
Movement of alleles from one population to another.
Genetic drift
variation in the frequency of different genotypes in a population, due to the chance disappearance of particular genes and alleles.
Bottleneck effect
A population bottleneck is the rapid reduction in the size of a population due to environmental events (such as earthquakes, floods, fires, disease, or droughts) or human activities (such as genocide).
Founder effect
When a population of reduced genetic diversity colonises a land and the colonising population is unrepresentative of the amount of alleles from the larger population in which they left.
Allopatric speciation
Occurs when a population becomes divided by a geographical barrier. This prevents gene flow by stopping sub-populations from interbreeding.
Forms of speciation
- parapatric (populations are separated and gene flow is possible but instead in individuals chose to breed with individuals iduals that are closer).
- sympatric speciation
- peripatric speciation
- allopatric speciation
Isolating mechanisms
Prezygotic: - geographical - morphological - behavioural - gamete mortality Postzygotic: - hybrid sterility
Evolution
Change in the genetic composition of populations over time.
Speciation
Evolution of a new species from an ancestral species.
Allopatric speciation steps
- Populations become separated by a geographical barrier that prevents gene flow.
- Two populations experience different selection pressures due to different environments and/ or mutations arising.
- Over time the two populations become so different that if brought back together they would be unable to produce viable and fertile offspring (and thus different species).
Disadvantages of selective breeding
Selectively bred populations low lower genetic variation which results in them being more susceptible to environment change and more genetic abnormalities can occur.
Selective breeding steps
- Choose the trait that is desired.
- Interbreed parents who most closely have the desired trait.
- Select the offspring with the best form of the trait and interbred these offspring.
- Continue this process until the population reproduces the desired trait.
