Question

Explain the significance of satellite DNA in DNA fingerprinting technique.

Answer 1

Hint: A DNA that contains number of repetitive short DNA sequences is known as satellite DNA. It is also known as satDNA or tandemly repeated DNA (TR-DNA).

Complete answer:
• DNA fingerprinting is a technique that is used to identify the nucleotide sequence in the specific region of sample DNA. This identification can help to recognize the person to whom a DNA sample belongs as this nucleotide sequence is unique for each person.
• The technique of DNA fingerprinting was first invented in the year 1984 by Sir Alec Jeffreys.
• DNA contains certain nucleotide sequences that are repetitive in nature and show high variations. These sequences are also unique in each person’s DNA. Further, these sequences are found in non-coding DNA. These DNA regions are called satellite DNA. A satellite DNA can consists of longer repeated sequence (known as minisatellites or Variable Number Tandem Repeats or VNTRs, about 10-100 base pairs or bp) or shorter repeated sequence (known as microsatellites or Short Tandem Repeats or STRs, about 2-4 bp).
• DNA fingerprinting involves studying nucleotide sequences of microsatellites or Short Tandem Repeats. Hence, it is also known as STR analysis now-a-days.
• The short nucleotide sequence in microsatellite or STR can be repeated about 5 to 50 times. The number of repeats is called allele. For example - D7S820 is a microsatellite or STR that is found on chromosome 7. It shows 5 to 16 GATA repeats.
• For DNA fingerprinting, the DNA is first extracted from a sample. The STR or microsatellite is subjected to PCR for amplification. The amplified STR DNA is now analyzed and matched with the DNA of a person whose identification needs to be done.

Note: DNA fingerprinting is known by different names like DNA profiling, forensic genetics, genetic fingerprinting, DNA typing, genotyping, STR analysis and identity testing. DNA fingerprinting is used in many applications. It is used to identify the criminal by matching the DNA of the suspect with the biological sample (hair, nail, blood etc) collected from the crime scene. It can also be used to determine paternity.