Inheritance is the passing of traits to offspring (from its parents or ancestors). This is the process by which an offspring acquires or becomes predisposed to the characteristics of its parents. At its most fundamental level, inheritance in individuals occurs by means of discrete traits, called genes. Humans have two different, discrete versions of the same gene called alleles. Individuals with two copies of the same allele of a given gene are called homozygous at that gene, while individuals with two different alleles of a given gene are called heterozygous at that gene.
The set of alleles an individual has for a specific gene is called its genotype, while the observable traits of an individual are called its phenotype. When individuals are heterozygous at a gene, often one allele is called dominant as its qualities dominate the phenotype, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.
When individuals reproduce, their offspring randomly inherit one of the two alleles from each parent. Moreover, the alleles of different genes get shuffled between parents to form offspring with many different combinations. However, in cases of genetic linkage, alleles do not assort independently.
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