Question

A gene that is 1,500 nucleotides long codes for a metabolic protein that is composed of 400 amino acids. The number of nucleotides in exons and introns are

• A. 1,200; 300
• B. 300; 1,200
• C. 1,500; 0
• D. 0; 1,500
• E. 400; 1,100

Answer 1

The correct option is A 1,200; 300

Each nucleotide triplet of RNA codes for one amino acid in the encoded protein. A RNA coding for the protein with 400 amino acids should have 400 x 3= 1200 nucleotides. This means the 1500 nucleotide long gene has 1200 nucleotides in exons and 300 nucleotides in introns. Exons are the nucleotide sequences that code for protein and the intervening introns are the non coding ones. Thus, the correct answer is option A.