DNA profiles can reveal family relationships
DNA samples can be analysed to explore possible paternal and maternal relationships between parents and children. This is possible because half of each person's chromosomes – humans have 23 pairs – half came from their mother and half from their father.
Each of the chromosomes contains many sections of non-coding DNA – DNA that does not seem to code for a protein, but contains areas called short tandem repeats (STRs). Each STR contains repeats of short sequences of bases, such as CATG in CATGCATGCATG.
When STRs are tested in DNA profiling, they occur in pairs. One chromosome in a pair carries an STR from the person's mother and the other chromosome in the pair carries an STR from the person’s father.
A person’s DNA profile as seen on an electrophoresis gel usually shows two lines for each of the STRs tested because usually the STRs inherited from the parents are of different lengths. Occasionally only one line appears because both STRs in a pair are of the same length.
When the DNA profile of a child is compared to the profiles of its genetic parents, it is possible to match one line in each STR area with a line in that area of the mother's profile. In this way, DNA profiling can also reveal non-paternity.
Three or four STRs, of very different sizes, are analysed when exploring family relationships.
DNA profiling in the media
Elizabeth Hurley, the British actor and cosmetics spokesperson, was recently in court to prove who the father of her baby was. The case was brought to the family court by her ex-boyfriend, Hollywood producer Stephen Bing.
DNA testing proved that Bing was indeed the father – this news came at a rather unfortunate moment, as Bing was waiting for results from a DNA test relating to another paternity case with a different person.
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