Genetic Variation

Allele

Different forms of a gene due to slightly different order of bases.

Allele Frequency

Measure of the frequency of a gene variant in a population.

Asexual Reproduction

Reproduction involving only one parent.

Co-dominance

Heterozygous individuals show the phenotype of both parents.

Crossing Over

During meiosis chromosomes exchange genetic information.

Evolution

The change in characteristics of a species over several generations.

Founder Effect

Variation loss from a small number establishing a new population.

Gene

A length of DNA that holds the instructions for a characteristic.

Gene Pool

Refers to the total number of genes of every individual in a population.

Genetic Drift

Change in allele frequency due to random chance alone.

Genotype

Genetic make-up of the organism (e.g. Bb, BB).

Heterozygous

Different forms of the allele are present in the genotype (e.g. Hh).

Homologous Chromosomes

Chromosome pairs (one from each parent) that are similar in length.

Homozygous

The same form of the allele is present in the genotype (e.g. HH).

Incomplete Dominance

Heterozygous individuals have a phenotype that is a blend of traits.

Independent Assortment

Homologous chromosomes line up at the equator randomly.

Lethal Allele

Alleles that produce a gene that kills the offspring.

Linked Alleles

Genes located on the same chromosome that are inherited together.

Meiosis

The type of cell division which produces gametes.

Migration

Movement of organisms into and out of a population.

Multiple Alleles

When three or more alleles occupy the same locus (e.g. blood types).

Mutation

A permanent change in the bases on the DNA.

Natural Selection

Heritable traits increase an organism’s chances of survival.

Pedigree Chart

A family tree which shows biological traits.

Phenotype

The physical expression of environmental factors and genotypes.

Population Bottleneck

Genetic drift caused by various events, such as a disaster.

Pure Breeding

A group of individuals that produce one gamete as they are homozygous.

Segregation

The process during meiosis which pairs of alleles are separated.

Selective Pressure

Evolutionary force that causes a particular phenotype to be more favorable.

Sexual Reproduction

Reproduction involving two parents; produces genetic variation.

Somatic Cells

If a mutation occurs in these cells, it will not be passed onto offspring.