Gene – A gene is the fundamental unit of heredity. It can be coding (i.e. code for a specific function or physical characteristic) or it can be non-coding. Each gene is located at a defined position (i.e. locus) on a particular chromosome and variations of the same gene are called alleles.

Genotype – The alleles present at a specific locus. In autosomal DNA, at each locus, there will be one allele from the child’s mother and one from the child’s father. Occasionally the mother or father donates 2 alleles, instead of one, and the child ends up with 3 alleles in total. This is called tri-allelic.

Genetic Marker – A gene that is phenotypically associated with a specific, easily identified trait and one which is used to identify an individual when compared to unrelated individuals.

Gestational Surrogacy – A process designed for women who cannot carry their own children. An embryo formed from a woman and man is carried by another woman who is unrelated to either the mother or father. The woman who carries the child is the gestational surrogate. The donors of the egg and sperm are called the biological or natural parents.