SomeTerms Used in Genetics

Genes carry encoded information about specific traits that are passed from parents to offspring. Each gene has a locus (location) on a chromosome. Diploid cells have two genes (a gene pair) for each trait. Each one is on a homologous chromosome.

Alleles are various molecular forms of a gene for the same trait that arise by mutation. If homozygous, both alleles are the same. If heterozygous, the alleles differ.

When heterozygous, one allele is dominant (A), and the other is recessive (a). Homozygous dominant = AA, homozygous recessive = a a, and heterozygous = Aa. A dominant allele masks a recessive allele that is paired with it.

Genotype refers to particular genes an individual carries. Phenotype refers to an individual's observable traits. You cannot always determine genotype by observing phenotype.

REVIEW: A heterozygote has a _____ for the trait being studied.
Answer pair of nonidentical alleles