Definitions

Trait

A characteristic determined by genetics.

P Generation

The original parent generation in a cross.

F1 Generation

First-generation offspring of the P generation.

F2 Generation

Offspring from crossing F1 individuals.

True-Breeding

Organisms that produce offspring identical to themselves when self-pollinated.

Allele

Variant form of a gene.

Dominant

Allele that masks the effect of a recessive allele.

Recessive

Allele only expressed in a homozygous state.

Phenotype

Observable traits.

Genotype

Genetic makeup.

Punnett Square

A diagram to predict offspring genotypes.

Homozygous

Having two identical alleles.

Heterozygous

Having two different alleles.

Hemizygous

Having only one allele of a gene, typical for males in X-linked traits.

Testcross

Cross with a homozygous recessive to determine an unknown genotype.

Monohybrid

Cross involving one trait.

Dihybrid

Cross involving two traits.

Law of Equal Segregation

Alleles separate equally into gametes.

Law of Independent Assortment

Genes on different chromosomes separate independently.

X-Linked

Gene located on the X chromosome.

Autosomal

Gene located on a non-sex chromosome.

Codominance

Both alleles in a heterozygote are fully expressed.

Trisomy

Condition with an extra chromosome.

Non-disjunction

Failure of chromosomes to separate properly during meiosis.

Pleiotropic

One gene influences multiple phenotypic traits.

Polygenic

Trait controlled by multiple genes.

Epistasis

Interaction where one gene affects the expression of another.

X Inactivation

Process by which one of the X chromosomes is silenced in females.