Allele

An allele is one of two or more alternative forms of a genetic sequence at a particular locus. Alleles can differ in DNA sequence and influence inherited traits.

Locus (genetics): A locus is a specific position on a chromosome occupied by a genetic sequence. Alleles are alternative sequence forms identified at the same locus.
Mendelian inheritance: Mendelian inheritance describes how alleles segregate and combine across generations under patterns identified by Gregor Mendel. Allele segregation explains the characteristic inheritance ratios in Mendelian crosses.
Allele frequency: Allele frequency is the proportion of copies of a genetic locus in a population that carry a specified allele. It quantifies how common an allele is across a population.
Single-nucleotide polymorphism: A single-nucleotide polymorphism is a common variation at one DNA base position in a population. It is one specific kind of sequence difference that may define alleles.
Gene: A gene is a DNA sequence that contributes to a functional product or regulation of biological activity. Many alleles are alternative forms of the same gene.
Meiosis: Meiosis is cell division that produces haploid reproductive cells with reshuffled chromosome combinations. It separates allele copies into gametes and recombines parental chromosomes.
Hardy–Weinberg principle: The Hardy–Weinberg principle predicts genotype frequencies from allele frequencies under specified assumptions about a population. It connects allele frequencies to expected genotype proportions.
Mutation: A mutation is a change in genetic material that can create a new DNA sequence variant. Mutation names a change; allele names a sequence form at a locus.
Chromosome: A chromosome is a DNA molecule, together with associated proteins, that carries genetic information. Alleles occupy loci along chromosomes.
Genetic recombination: Genetic recombination is the exchange or rearrangement of DNA that creates new combinations of genetic variants. Recombination changes which alleles are inherited together.

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