Glossary – Modes of inheritance: single gene or polygenic?

Use the alphabetical glossary below to remind yourself what the terms in the course mean.

Is there a term missing from the vocabulary used in the course? Tell me in the comments box below and I'll add it to the glossary.

Allele – an alternative form of a gene; also called variant.

DNA (deoxyribonucleic acid) – chain-like molecule that carries an individual’s genes. Packaged as chromosomes in every cell.

Epigenome – regulatory factors that influence the reading of an individual’s genes. We have learned about epigenetics in the first part of the course.

Indirect selection – a situation where breeding for one trait changes other traits at the same time. Indirect selection is due to genetic association between traits.

Phenotype – the appearance of an individual, a visible characteristic.

Genetic correlation – measure of genetic association between traits. Genetic correlation is due to the same genes, or genes close to each other, influencing the two traits.

Genetic relationship – the proportion of DNA (gene alleles) shared by two individuals.

Genome – all the genetic material of an individual, all the DNA.

Genotype – an individual’s alleles for a particular gene or trait.

Candidate gene – a candidate gene that is being tested for the possibility of causing or contributing to the development of a trait.

Categorical trait – a polygenic trait in which phenotypes are grouped into defined categories.

Chromosome – consists of the DNA strand.

Qualitative trait – see monogenic trait.

Quantitative trait – see polygenic trait.

Threshold trait – a trait that becomes apparent in the phenotype when the number of alleles causing the trait exceeds the threshold.

Linkage – genes are so close together on the chromosome that they are usually inherited together.

Locus – the address of the gene; the location of the gene on the chromosome.

Mendelian trait – see monogenic trait.

Polygenic trait – a trait that is controlled by more than one gene, usually dozens or even thousands.

Complex trait – a polygenic trait that is influenced by a variety of factors in addition to genes.

Mutation – a change in the DNA code; a genetic error.

Heritability – a measure of the amount of genetic variation in a trait – what proportion of the variation between individuals in the trait is due to hereditary factors. More on heritability in part five of the course.

Pleiotropy – a gene controls more than one trait.

Polygenic trait – a trait that is controlled by more than one gene.

Segregation analysis – statistical analysis that can be used to investigate the existence of a possible major gene.

Snip – see SNP marker.

SNP marker also known as snip – base differences in the DNA code between individuals.

Major gene – a gene that has a large effect but explains only part of the variation seen in a trait.

Crossing over – exchange of fragments between the homologous chromosomes (chromosome pair coming from the sire and the dam)

Variant – allele; alternative form of a gene.

Control – a healthy individual, whose DNA sample is compared with a diseased individual to search for causative mutations.

Monogenic trait – a trait that is controlled by a single gene.

Is there a term missing from the vocabulary used in the course? Tell me in the comments box below and I’ll add it to the glossary.