DNA Fingerprinting & Satellite DNA — NEET Biology
✅ Asked in NEET 2021DNA fingerprinting involves identifying differences in specific DNA regions called: (NEET 2021)
DNA fingerprinting involves identifying differences in specific DNA regions called: (NEET 2021)
Answer & NCERT explanation
Correct answer: B — Repetitive DNA
DNA fingerprinting relies on identifying differences in repetitive DNA sequences, particularly Variable Number Tandem Repeats (VNTRs) and Short Tandem Repeats (STRs). These repetitive sequences vary in number between individuals, creating unique patterns. Single nucleotides are too small, satellite DNA is a type of repetitive DNA, and polymorphic DNA is a broader term that includes repetitive DNA variations.
Read more NCERT concept on the PYQ
DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA, because in these sequences, a small stretch of DNA is repeated many times. These repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation. The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA. Depending on base composition (A: T rich or G:C rich), length of segment, and number of repetitive units, the satellite DNA is classified into many categories, such as micro-satellites, mini-satellites etc. These sequences normally do not code for any proteins, but they form a large portion of human genome. These sequence show high degree of polymorphism and form the basis of DNA fingerprinting. Since DNA from every tissue (such as blood, hair-follicle, skin, bone, saliva, sperm etc.), from an individual show the same degree of polymorphism, they become very useful identification tool in forensic applications. Further, as the polymorphisms are inheritable from parents to children, DNA fingerprinting is the basis of paternity testing, in case of disputes.
NTA tests whether you understand that DNA fingerprinting relies on repetitive DNA sequences (satellite DNA), not protein-coding regions. These sequences show high polymorphism, making them ideal for identification in forensics and paternity testing. Students often confuse satellite DNA with regular genomic DNA or forget that these repetitive sequences are actually non-coding. Key mistake: thinking fingerprinting uses unique genes—it doesn't. Satellite DNA's high variability between individuals is what makes identification possible. Remember: repetitive DNA = satellite DNA = polymorphic = useful for fingerprinting. The inheritable nature of these polymorphisms is crucial for paternity disputes.
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