Question

The basis of DNA fingerprinting is

• A. The double helix
• B. Error in base sequence
• C. Polymorphism in sequence
• D. DNA replication
• E. DNA coiling

Answer 1

The correct option is C

Polymorphism in sequence

The correct option is C

Explanation of the correct option:

1. DNA fingerprinting is an important technique that is used to identify the nucleotide sequences of DNA that are unique for an individual.
2. Sequence polymorphisms, which are tiny sequence variations (usually single base-pair changes) within individuals, are used in DNA fingerprinting.
3. Based on the position of restriction sites in the genome, restriction enzymes can digest the entire genome into DNA fragments of a specific length.
4. Variation in the size of DNA fragments produced by digestion with a given restriction enzyme is caused by sequence polymorphism, which affects restriction enzyme recognition sites.
5. Southern blotting can discover these differences, which are restriction fragment length polymorphisms (RFLPs).

Explanation of the incorrect option:

Option A:

1. The term "double helix" is used in genomics to describe the physical structure of DNA.
2. A DNA molecule is made up of two connected strands that loop around each other in a helix-like structure, resembling a twisted ladder.
3. The backbone of each strand is made up of sugar (deoxyribose) and phosphate groups that alternate.

Option B:

1. Error in the secondary structure of the final DNA molecule results from incorrectly paired nucleotides.
2. Enzymes recognize and correct these abnormalities during mismatch repair by removing the incorrectly matched nucleotide and replacing it with the correct nucleotide.

Option D:

1. During cell division, DNA replication is the process by which DNA copies itself.
2. The initial stage in DNA replication is to 'unzip' the DNA molecule's double helix structure.

Option E:

1. A higher-order DNA structure can be described by DNA supercoiling.
2. The interwinding of two complementary strands around one another and a common helical axis is termed the double-helical structure of DNA.
3. The DNA supercoils structure is defined by the writhing of this helical axis in space.

Final Answer: The basis of DNA fingerprinting is polymorphism in sequence.