Glossary

Allele: a piece of genetic material at a specific location (locus) of the chromosome. Each individual has a chromosome pair where there are two alleles, which can be identical (homozygosis) or not (heterozygosis). Alleles are responsible for a range of inherited characteristics, such as blood type or hair colour.

Chromosome: a thread-like structure of DNA found in the nucleus of most living cells, which encode for hundreds or thousands of genes that make and maintain the human body. Humans have 46 chromosomes, arranged in 23 pairs. Each chromosome pair consists of one chromosome inherited from the mother and one from the father. 22 of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females. Females have two copies of the X chromosome, while males have one X and one Y chromosome.

Combined Paternity Index: is a likelihood that this man is the biological father of this child compared to a person chosen at random from a validated population. Paternity is usually accepted if this number is greater than 1000.

Genome: the entire set DNA which is present in the cell nucleus, and includes all the autosomal chromosomes, and both sex chromosomes.

DNA: a molecule, found in the cell nucleus, which carries the instructions for the development of an organism. DNA stores information that is passed down from one generation to the next (half from the mother and half from the father), providing a map of genetic characteristics.

As DNA is in almost all living cells it can be found in saliva, hair and blood for example. These are some of the most common sources that DNA testing samples are analysed from.

Gene: Part of the DNA sequence that carries the information for the formation of protein. Genes are inherited from parents to their descendants and give information, which is needed for the formation and development of an organism.

Genotype: the collection of genes responsible for the various genetic traits of a given organism.

Maternity: the state of being a child’s biological mother.

Mutation: a change in the genetic material of a living organism. Mutations can occur during DNA replication, or can be caused by external factors such as exposure to smoking, sunlight or radiation. Some mutations can be harmful and cause disease, others small mutations may have no noticeable effects.

Nucleotide: the basic unit of our DNA. In human DNA there are four different nitrogenous bases (Cytosine (C), Guanine (G), Thymine (T) and Adenosine (A)) and, consequently, four different nucleotides.

Paternity: the state of being a child’s biological father.

Probability of Paternity: the percentage likelihood that a man with the alleles of the alleged father is the biological parent of the child, as compared to an untested, unrelated man of the same race.

SNP (Single Nucleotide Polymorphism): polymorphism at specific DNA site (locus), which occurs because of the substitution of one nucleotide with another (i.e. A -> C). It represents a variation in the genetic makeup, which differs among people. These variations can be numerous because there are approximately 10 million SNPs in the human genome.