Question

In a new species of bacteria, tRNA anticodons are recognized by two nucleotide bases instead of three. What would be the number of amino acids and the number of peptide bonds, respectively, of a polypeptide encoded by a 120 nucleotide long coding DNA sequence which includes a two-base stop codon?

Answer 1

For a hypothetical bacterial species with tRNA anticodons recognized by two nucleotide bases, a 120 nucleotide coding DNA sequence including a two-base stop codon would encode a polypeptide of 59 amino acids and contain 58 peptide bonds.

Step-by-step explanation:

In a hypothetical bacterial species where tRNA anticodons are recognized by two nucleotide bases instead of three, the number of possible amino acids would be significantly reduced. Since an anticodon composed of two nucleotides can only produce 16 different combinations (42), it would not be able to code for all 20 standard amino acids found in proteins.

However, for a 120-nucleotide-long coding DNA sequence that includes a two-base stop codon, we would first have to remove the stop codon bases to find the number of nucleotides available for coding amino acids. This leaves us with 118 nucleotides. Dividing this by 2 bases per amino acid results in a polypeptide chain length of 59 amino acids. The number of peptide bonds in a polypeptide is always one less than the number of amino acids, hence there would be 58 peptide bonds.