Genetic Definitions

Gamete

Organisms reproductive cell (egg / sperm). Has half number of chromosomes (23)

Genome

Entire DNA of an organism

Chromosome

Structure found in the nucleus, made from a long strand of DNA.

Gene

Short section of DNA that codes for a protein, therefore a characteristic. Most characteristics are many genes, some are a singular gene.

Allele

Different forms of a gene. Humans have 2 alleles for each gene: 1 from each parent.

Dominant allele

Only one is needed for it to be expressed and the corresponding phenotype to be observed.

Recessive allele

2 copies are needed for it to be expressed and for the corresponding phenotype to be observed

Genotype

Combination of alleles an individual has e.g. Aa

Phenotype

Physcial characteristics observed in the individual e.g. eye colour

Homozygous

Both inhereted alleles are the same (2 dominant or 2 recessive)H

Heterozygous

One inherited allele is dominant and one is recessive

Codominance

Neither allele is dominant over the other; both contribute to the phenotype. e.g. white chicken and black chicken have offspring that are speckled, so the chicken is codominant.