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What is it that forms the basis of DNA fingerprinting?
A
Satellite DNA occurring as highly repeated short DNA segments
B
The relative proportions of purines and pyrimidines in DNA
C
The relative difference in the DNA occurrence in blood, skin and saliva
D
The relative amount of DNA in the ridges and grooves of the fingerprints
Detailed Solution
About 99.9% of the base sequence of DNA is the same in all humans; DNA fingerprinting looks at the regions that differ.
These regions are repetitive DNA, in which a small stretch of DNA is repeated many times; they form satellite peaks during density-gradient centrifugation and are called satellite DNA (mini-satellites and micro-satellites).
These sequences show a very high degree of polymorphism: the number of repeats (VNTR) differs from person to person and is inherited.
This polymorphism in satellite DNA is the basis of DNA fingerprinting.
The ratio of purines to pyrimidines is the same (1 : 1) in everyone, and the DNA of all tissues of a person (blood, skin, saliva) is identical, so these cannot be the basis.
Hence the basis is satellite DNA occurring as highly repeated short DNA segments.
These regions are repetitive DNA, in which a small stretch of DNA is repeated many times; they form satellite peaks during density-gradient centrifugation and are called satellite DNA (mini-satellites and micro-satellites).
These sequences show a very high degree of polymorphism: the number of repeats (VNTR) differs from person to person and is inherited.
This polymorphism in satellite DNA is the basis of DNA fingerprinting.
The ratio of purines to pyrimidines is the same (1 : 1) in everyone, and the DNA of all tissues of a person (blood, skin, saliva) is identical, so these cannot be the basis.
Hence the basis is satellite DNA occurring as highly repeated short DNA segments.