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Biology Unit 4
Topic 6: Infection, Immunity and Forensics
5. Describe how DNA profiling is used for
identification and determining genetic relationships
between organisms (plants and animals).
The human genome contains between 20 000 and 25 000 genes and the chromosomes are
made up of hundreds of millions of base pairs .
Over 90% of the DNA is made up of introns and other repetitive coding regions between
the genes. Their function is not yet fully understood.
Introns are the regions of the chromosomes that are used in DNA profiling . Within introns,
there are short sequences of DNA that are repeated many times to form micro-satellites
and mini-satellites. These are called short tandem repeats (STRs).
The same mini- or micro- satellites appear in the same positions on each pair of
homologous chromosomes . However, the number of repeats of each satellite will vary as
different patterns may be inherited from your mother and father .
There are many different introns, and a huge variationin the number of repeats. The
likelihood of any 2 individuals having the same pattern of DNA is extremely remote (unless
they are identical twins).
The more closely related 2 individuals are, the more likely it is that similarities will be
apparent in their DNA patterns .
Uses of DNA profiling
Paternity to find out if the alleged father is actually the biological father of the child
Twins identical twins share the same genetic material while fraternal twins develop from
two eggs fertilised by 2 sperm and are no more alike than individual siblings born at
different times. It can be difficult to tell at birth whether twins are identical or fraternal
Siblings for example, adopted people may want to have DNA tests to make sure that
alleged biological siblings are actually their blood brothers or sisters
Immigration some visa applications may depend of proof of relatedness
Criminal justice DNA testing can help solve a crime by comparing the DNA profile of
suspects to offender samples. Victorian law allows the collection of blood and saliva
samples from convicted criminals and suspects. DNA profiles are then kept on a database
STR analysis in transplantation
Resolving specimen identity in anatomic pathology, DNA identity testing can be used to
determine the origin of mislabelled or mishandled specimens
It can also be used in: agriculture ,forensic science , medical diagnosis , in the food
industry and to confirm the pedigree of domestic animals
Text Book: p. 78