Distinguishing the individuals according to their DNA print pattern is termed as DNA fingerprinting. It is also called DNA profiling or molecular fingerprinting. It is used to assess whether an individual has a genetic relationship with supposed individuals or not. Satellite DNA’s are unique to an individual. Satellite DNA’s of different individuals are hybridized with a single type of radiolabeled probe DNA by using Southern blotting method. Then an autoradiogram is taken to get a DNA print pattern of the individuals. From this DNA print pattern, the individuals are distinguished on the basis of bands in their DNA prints.
Satellite DNA is a non-coding region of eukaryotic cells having tandem repeats of a sequence. It is also called as mini-satellite. It is rich in GC pairs and 9-40 bp in size. Some minisatellites exist in a single copy, but others represent 2 or more copies.
Methodology of DNA Fingerprinting
- Isolation of cell DNA
- Restriction digestion
- Gel electrophoresis
- Southern blotting
- Selection of DNA probe
- Filter hybridization
- Analysis of DNA print pattern.
Application of DNA fingerprinting
DNA fingerprinting has been used to settle disputed parentage, murder cases, distinguish rapists and to analyze the genetics of various organisms.
- To settle disputed parentage
In some abnormal cases, courts cannot decide who is the real father or mother or both of a child. So, it is difficult to settle the case. DNA fingerprinting is used to settle the case. In 1984, a Ghanaian family with a mother, two sons, and two daughters, went to enter Britain. The immigration authorities refused the entry of one boy into the Britain, as they thought that the boy was not her son. But the woman said that the boy was his own son. Studies on enzymes, antiserum, and erythrocytes didn’t help to solve the problem. A. Jeffreys made 2 DNA fingerprinting patterns from DNAs isolated from all members of the family using two multilocus probes. They identified 25 maternal-specific bands out of 61 bands in the boy’s DNA print. Hence, they concluded that the boy was her own son. Finally, the family was allowed to enter the Britain.
- To settle murder cases
DNA fingerprinting helps the police and law courts to settle some complicated murder cases. By using DNA fingerprinting, a man charged for many years with a murder case was shown to be innocent and left free from jail. It happened in the Britain in 1987.
- To distinguish the Rapist
If a lady was raped by a man on a dark night and she was unable to find out the man at that time, then DNA fingerprinting helps to distinguish the accused from men arrested doubtfully.
DNA fingerprinting pattern is made from DNAs taken from vaginal swab and semen or blood of doubtful persons. If the DNA print of the vaginal swab matches with the DNA print of any one man with 100 % certainty, it is confirmed that the particular man is accused of the rape.
- Pedigree analysis
DNA fingerprinting is used in the pedigree analysis in cat, dog, horses, and man.
- Migration pattern
It is used to assess the pattern of migration of ancient populations.
- Genetic analysis
It is also employed in the genetic analysis of various strains of agricultural crops and animals.
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