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BI1051 Population Genetics
Terms in this set (65)
The body of mathematical principles that explain how genetic variation changes in populations.
A group of sexually interbreeding individuals.
Frequency of homozygotes + 1/2 (frequency of heterozygotes).
The sum of all alleles within a population with the potential to contribute to the next generation.
Hardy Weinberg Principle
In a population at equilibrium both gene and genotype frequencies remain constant from generation to generation. Assumptions: large population, random mating, no mutations, no migration, no selection.
p2 + 2pq + q2 = 1
p+q = 1
p+q+r = 1
Have a high carrier frequency in a population.
A change in the DNA sequence at a specific locus. Creates genetic variation.
The process that modifies the reproductive success of an organism in its natural environment.
Gain or loss of individuals that make up the gene pool.
Random fluctuations in gene frequencies of small populations mainly due to small population size. Effect population size ~ number of breeders.
Would expect them to be eradicated by natural selection. Why do they remain? Late onset (after reproduction), high mutation rates (accumulate mutations at high levels), heterozygote advantage (advantage over dominant homozygote despite recessive being fatal).
Example of application of population genetics. Used in paternity testing and forensic science.
Can estimate the risk of transmitting a disease to children.
A hypothesis that has been verified by factual evidence.
The process of temporal change by which organisms come to differ permanently from their ancestors with respect to heritable traits.
Characteristics passed on from parents to offspring.
Evolution within a lineage. It is a transformation.
The division of a lineage due to genetic divergence. The splitting or branching of a lineage. Subsequent anagenesis will occur in both sister lineages.
Branched evolutionary histories.
The study of branches evolutionary histories.
Evolution at the population level. 'Within species' evolution including the processes leading up to speciation. I.e. intraspecific competition.
How gene pools (populations) change over time in the relative abundance of genotypes or phenotypes.
Comprised of one or more populations of many individuals.
Evolution at the species level and above. Involves speciation and subsequent divergence of species and higher taxa. I.e. interspecific competition.
Any measureable item on an organism (e.g. height). Also referred to as traits.
Alternative variants of a character (e.g. eye colour in humans).
The information stored in the DNA of one individual (genes).
Contains the nuclear genome. Contains linear chromosomes.
Contains the mitochondrial genome, a circular chromosome. Derived from an endosymbiont bacteria.
Sequences within introns of genes and those between genes. Assumed not to be subject to natural selection.
Single nucleotide polymorphism. Nucleotide base sequences making up the same gene may differ between individuals.
When nucleotide sequences differ in this manner at the same site (locus) on the paired (homologous) chromosomes. The locus is said to be polymorphic.
The combination of alleles at one or more studied/ examined loci in one individual.
The observable/ measureable/ detectable characteristics of an organism. Compromises all observable non-gene traits. It is the easiest to observe and is heritable.
Examples include nests and other structures.
Intra population variation
Heritable. Essential for evolutionary change to occur. There must be a sufficient amount of such variation.
A water mould capable of rapid evolution. Estimated to have caused more than 1 million deaths and forced 2 million to emigrate from Ireland. Potatoes were propagated asexually. Could have been averted if the population had been more genetically diverse.
Black sigatoka disease
In bananas. Problem made worse by: cultivation of few varieties all of which are vulnerable, propagated asexually, fungus has genetic variability so evolved resistance to fungicides.
One or a few gene loci involved. Usually only a few alleles involved at such loci. Allele-for-trait effect clearly evident in phenotype.
Many gene loci involved. Many alleles involved. It is harder to discern the contribution of the individual alleles to the phenotype.
A method of quantifying population variation requiring representative and unbiased samples. Take a random and large sample.
Used for continuous variation.
For discontinuous variation.
Shuffles genetic variation but does not make new genetic variation.
Non random changes in allele frequencies. Can be artificial or natural.
Mating between relatives.
Non-random association between loci. There is a correlation.
Random association between loci.
Adaptive evolutionary change
When subjected to selection, heritable phenotypic traits correlating with fitness will alter in frequency within a population. This is directed change in response to environmental variables.
The proportion of the variant within the population as a whole will increase in the next generation. The variant may have a selective advantage over the normal form.
The breeder/ experimenter decides fitness of traits. Results in adaptive evolution under artificial conditions. Does not necessarily correspond to differential fitness under natural conditions.
Selectively neutral genes
Genes whose frequencies are not influenced by natural selection. Neutral genes that hitch hike with genes that are adaptive are subject to selection.
Neutral evolutionary change
Frequencies of variants of neutral traits can change over time within a population. Undirected evolutionary change.
Multiple phenotypic effects of an individual gene.
Selection that gets rid of undesirable characteristics.
Selection where a trait is very fit for the habitat so gets fixed in a population.
Selection that is between positive and negative. Variation is needed and so there is equal frequencies and never fixation.
Adaptive traits are correlated with fitness. Neutral phenotypic traits are not.
Adaptive and especially neutral traits subject to random change. They can occur due to random processes e.g. genetic drift.
The phenotypic expression of the genotype is often environmentally determined.
Adaptive phenotypic plasticity
Each of the different phenotypic expressions of genotype are beneficial.
The genome is coevolved, integrated assemblage of genes. It cannot be simply unravelled to produce a radically new structure.
Body size must take into account respiratory demands and bodies collapsing under their own weight.
A constraint found within the entire group of descendants from a common ancestor.
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