Genetics: Allele and Genotype Frequencies

A group of individuals of the same species living in the same area at the same time, capable of interbreeding.

The total collection of all alleles for all genes within a population.

The relative frequency of a particular allele within a population.

An individual with two copies of the same allele for a specific gene.

An individual with two different alleles for a specific gene.

The total number of occurrences of a particular genotype in a population.

The combination of alleles an individual possesses for a specific gene.

The Hardy-Weinberg principle describes the stability of allele frequencies in a population across generations under specific conditions. It predicts that these frequencies remain constant in absence of disturbances like mutations, gene flow, genetic drift, non-random mating, and natural selection.

The equation p + q = 1.0 represents the sum of allele frequencies for a gene with two alleles. 'p' represents the frequency of the dominant allele (A), and 'q' represents the frequency of the recessive allele (a).

The Hardy-Weinberg equation, p² + 2pq + q² = 1.0, predicts the frequencies of genotypes in a population. p² represents the frequency of homozygous dominant (AA), 2pq represents the frequency of heterozygous (Aa), and q² represents the frequency of homozygous recessive (aa).

The Hardy-Weinberg principle assumes that the population is large, meaning that there are enough individuals to prevent random fluctuations in allele frequencies due to chance events. Changes due to chance are more significant in smaller populations.

The Hardy-Weinberg principle assumes that mating within the population is random. This means that individuals choose mates irrespective of their genotypes. Non-random mating, such as inbreeding, can alter allele frequencies.

The Hardy-Weinberg principle assumes that new mutations are not introduced into the population. Mutations can change the genetic makeup of a population by creating new alleles.

The Hardy-Weinberg principle assumes no gene flow, meaning no exchange of alleles between populations. Migration or movement of individuals can change allele frequencies through the introduction or removal of genes.

The Hardy-Weinberg principle assumes that there's no natural selection, meaning that all genotypes have equal survival and reproductive rates. Selection pressures can favor certain genotypes, leading to changes in allele frequencies.

Sickle cell anaemia is a genetic disorder caused by a mutation in the gene responsible for haemoglobin production, resulting in abnormally shaped red blood cells. Individuals with sickle cell anaemia have the HbSHbS genotype.

Heterozygote superiority occurs when the heterozygous genotype is more advantageous than either homozygous genotype.

Directional selection favors individuals with traits that deviate from the mean in a specific direction, leading to a shift in the population's average phenotype over time.

Stabilising selection favors individuals closest to the average phenotype, reducing variation and maintaining the status quo.

Selection pressures, such as competition for resources, predation, and disease, influence the survival and reproduction of individuals in a population, impacting allele frequencies.

The gene pool consists of all the alleles of all the genes present within a population at a given time.

Environmental factors can act as agents of change, influencing the direction of evolution through selection pressures.

Disruptive selection favors individuals at both extremes of a trait range, leading to increased diversity within a population.

The frequency of an allele within a gene pool is influenced by selection pressures, acting on the fitness of different genotypes.

Antibiotic resistance in bacteria is an example of directional selection, where the ability to withstand antibiotics becomes advantageous and increases in frequency.