Genetic phenomena

Genetic phenomena are observable patterns and effects arising from genes, genetic variation, inheritance, and interactions between genes and their environment.

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Gene: A DNA sequence that contributes to a functional product or regulates its production. Genes are the basic units whose activity and variation underlie genetic phenomena.
Mendelian inheritance: The transmission of genetic traits according to segregation and independent assortment of alleles. Its rules explain many simple, predictable inheritance patterns.
Incomplete dominance: An inheritance pattern in which a heterozygote has an intermediate phenotype between the two homozygotes. It demonstrates that heterozygotes need not resemble either homozygous form.
Natural selection: A process in which heritable differences cause individuals to leave different numbers of descendants. Genetic variants that affect reproduction can change in frequency through selection.
Allele: One of two or more alternative forms of a genetic sequence at a particular genomic location. Different alleles can produce distinct inherited effects.
Dominance (genetics): A relationship in which one allele’s effect masks or modifies another allele’s effect in a heterozygote. Dominance determines how paired alleles appear in heterozygous individuals.
Codominance: An inheritance pattern in which both alleles are detectably expressed in a heterozygote. It contrasts with masking patterns by making both allele effects observable.
Genetic drift: Random changes in allele frequencies caused by sampling across generations. It changes genetic variation even when variants have no fitness advantage.
Genotype: The genetic constitution of an organism, either at specified loci or across its genome. Genotype provides the inherited genetic inputs that contribute to observable patterns.
Epistasis: An interaction in which variation at one genetic locus alters the effect of variation at another. Epistasis shows how one gene can change the phenotypic effect of another.