Allele - A variant form of a gene. Some genes have a variety of
different forms, which are located at the same position, or genetic
locus, on a chromosome.
different forms, which are located at the same position, or genetic
locus, on a chromosome.
DNA - A large organic molecule that stores the genetic code for the synthesis of proteins.
DNA is composed of sugars, phosphates and bases arranged in a double helix shaped
molecular structure. Segments of DNA in chromosomes correspond to specific genes.
DNA is composed of sugars, phosphates and bases arranged in a double helix shaped
molecular structure. Segments of DNA in chromosomes correspond to specific genes.
Genetics - The study of gene structure and action and the patterns
of inheritance of traits from parent to offspring.
Dominant - An allele that masks the presence of a recessive allele in
the phenotype. Dominant alleles for a trait are usually expressed
if an individual is homozygous dominant or heterozygous.
the phenotype. Dominant alleles for a trait are usually expressed
if an individual is homozygous dominant or heterozygous.
Recessive - An allele that is masked in the phenotype by the
presence of a dominant allele. Recessive alleles are expressed in the
phenotype when the genotype is homozygous recessive (aa).
presence of a dominant allele. Recessive alleles are expressed in the
phenotype when the genotype is homozygous recessive (aa).
Genotype - The genetic makeup of an
organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits. |
Phenotype - A variant form of a gene. Some genes have a variety of
different forms, which are located at the same position, or genetic locus, on a chromosome. |
Heterozygous - A genotype consisting of two different alleles
of a gene for a particular trait (Aa). Individuals who are
heterozygous for a trait are referred to as heterozygotes.
of a gene for a particular trait (Aa). Individuals who are
heterozygous for a trait are referred to as heterozygotes.
Homozygous - Having the same allele at the same locus on both
members of a pair of homologous chromosomes. Homozygous
also refers to a genotype consisting of two identical alleles of
a gene for a particular trait. An individual may be homozygous
dominant (AA) or homozygous recessive (aa). Individuals who are
homozygous for a trait are referred to as homozygotes.
members of a pair of homologous chromosomes. Homozygous
also refers to a genotype consisting of two identical alleles of
a gene for a particular trait. An individual may be homozygous
dominant (AA) or homozygous recessive (aa). Individuals who are
homozygous for a trait are referred to as homozygotes.
Punnet Square - A simple graphical method of showing all of the potential
combinations of offspring genotypes that can occur and their probability given the parent genotypes. See example below. Punnett squares are commonly used by genetics counselors to predict the odds of a couple passing on particular inherited traits.
combinations of offspring genotypes that can occur and their probability given the parent genotypes. See example below. Punnett squares are commonly used by genetics counselors to predict the odds of a couple passing on particular inherited traits.