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GATE 2025 BT – Question 31

Genetics, Cellular and Molecular Biology · Molecular Biology: Structure of genes and chromosomes, mutations and mutagenesis, regulation of gene expression · 1 mark · Numerical answer

The contour length of a B-DNA molecule that encodes a bacterial protein of 33 kDa is ______ nm.

Consider the average molecular weight of an amino acid as 110 Da and helix rise per base pair for B-DNA as 0.34 nm. (Round off to the nearest integer)

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Correct answer: 306

Explanation

The protein has $\frac{33000}{110} = 300$ amino acids. Each is coded by 3 base pairs, so the gene has 900 bp. The contour length is $900 \times 0.34 = 306$ nm.