Question

Amino acid residues in proteins are each specified by three contiguous bases. What is the contour length of a segment of B-DNA that encodes 50-kD protein?

Short answer

The contour length of a segment of B-DNA is 4616 Åor 0.46 µm.

Step-by-step solution

Conversion of 50-kD protein into D

The conversion formula is as follows:

1 - kD = 1000 D

Then, for 50 - kD,

50 - kD = $50\times 1000$

=50,000 D

Determination of the number of amino acids in  protein

The average molecular mass of one amino acid is 110D , then the number of amino acids can be obtained by the following,

$\frac{50,000D}{110D}=455$

Therefore, there are 455 residues of amino acids in 50,000D protein.

Obtaining the number of nucleotides

A codon, a triplet of nucleotides, encloses one amino acid.This means 455 residues of amino acids will be encoded by,

$455\times 3=1365$

Thus, the protein is enveloped by 1365 nucleotides.

Calculation of the contour length

The rise for every base pair in B-DNA is 3.4A. This exhibits that the length of 1365 base would be,

$1365\times 3.4=4641A$

Hence, the contour length of a segment of B-DNA that encodes a 50-kD protein is 4616 Åor 0.46 µm.