Inheritence

Incomplete Dominance

A pattern of inheritance where neither allele for a characteristic completely masks the effects of the other; results in a blend of traits for the characteristics. When a heterozygous individual has a phenotype intermediate to those of corresponding homozygous individuals.

Test Cross

A cross between an organism displaying the recessive trait of a characteristic and one showing the dominant trait, to determine whether the dominant phenotype is due to a homozygous or heterozygous genotype; this only applies if a large number of offspring are produced.

Frequency Histogram

An accurate representation of the distribution of numerical data and is an estimate of the probability frequency distribution of a continuous variable (quantitative variable).

Trait

Heritable characteristic; phenotype.

Sex-linked

A gene located on sex chromosome.

Second Filial Generation (F2)

The offspring of F1 generation; second generation produced from original cross between two parents (P)

First Filial Generation (F1)

The first generation of offspring produced from a cross between two parents (P)

Dihybrid Ratio

Predicted ratio of offspring obtained from a cross between individuals simultaneously heterozygous for two characteristics.

Parental Generation (P)

Two individual organisms originally crossed in a breeding experiment; their offspring are the F1 generation.

Dihybrid Cross

Genetic cross between two individuals, both heterozygous for two specific traits.

Punnett Square

A mathematical device used to calculate probabilities of genetic crosses.

Phenotype

Actual express of the genotype.

Genotype

The genetic makeup of an individual.

Recessive Allele (autosomal recessive)

An allele found on an autosomal chromosome that can be masked by its dominant form in the heterozygous condition; can be autosomal or sex-linked.

Recessive Trait

Trait due to an allele that can be masked by the dominant allele in the heterozygous condition but expressed in the homozygous condition.

Dominant Allele (autosomal dominant)

An allele for a gene that overrides the effects of the recessive allele in the heterozygous condition; can be autosomal or sex-linked.

Dominant Trait

The particular trait of a characteristic that is expressed in the phenotype of a heterozygous individual.

Wild Type

The most common or normal form of a particular gene or trait in a population.

Hybrid

The offspring of a cross between two organisms that differ in one or more genetic traits.

Pure-bred

An organism that is homozygous for a particular trait.

Heterozygous

An organism that has two different alleles for a particular trait.

Homozygous

An organism that has two identical alleles for a particular trait.

Allele

Different versions of a gene that contribute to variations in a particular trait.

Monohybrid Cross

A genetic cross involving the inheritance of a single trait or gene.

Heredity

The genetic transmission of traits from parents to offspr