Content Advisory
Please be aware that this content contains descriptions of violence that may be distressing to some viewers.An interactive tool used to supplement the NIJ online training course entitled 'Principles of Forensic DNA for Officers of the Court', as outlined in the second learning module, 'Biology of DNA'. This brief animation shows homozygous and heterozygous genotypes on a pair of chromosomes and is used as biological DNA terminology.
Transcript
Type at any particular locus on a pair of chromosomes can be characterized as either homozygous or heterozygous. If that locus displays two alleles that are the same, its genotype is referred to as homozygous; if the locus displays two different alleles, that genotype is referred to as heterozygous. Note that there are two possible homozygous genotypes: in this case homozygous brown or homozygous blonde. There is, however, only one heterozygous genotype possible at any particular locus, although there are two ways to achieve it: the brown allele can be inherited from the father and the blonde from the mother or vice versa, but the genetic outcome is the same either way. The genotype displays one of each possible allele.