Glossary of genetics terms

Allele = alternate forms of a gene

Gene = segment of DNA, which codes for a particular trait or a protein

Dominant allele = allele that masks the expression of another allele

Recessive allele = allele that is masked by a dominant allele

Homozygote = individual with two copies of the same allele (e.g., TT or tt)

Heterozygote = individual with copies of two different alleles (e.g., Tt or Rr)

Phenotype = the physical appearance of an organism

Genotype = the genetic makeup of an organism

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Last updated May 9, 1997.