Question

Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying leucine, Leu). What will be the effect on translation in this cell?

A. One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones.
B. The altered tRNA will result in an amino acid variant in all copies of the protein.
C. The altered tRNA will be so unstable that it will not participate in translation.
D. The altered tRNA will cause this mRNA to make only nonfunctioning product.
E. The tRNA-Leu will not be able to enter the ribosome to bind to the UUA codon.

Answer 1

An error in tRNA anticodon causes it to mispair with mRNA codons, leading to potential misincorporation of amino acids during translation, which might result in some fraction of proteins with amino acid sequence variations.

Step-by-step explanation:

Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. This altered tRNA molecule, which still attaches to the same amino acid phenylalanine (Phe), now has an anticodon loop with the sequence AAU. This anticodon allows it to bind to the UUA codon on mRNA, which usually codes for leucine (Leu). As tRNAs bring specific amino acids to the growing polypeptide chain based on the codon-anticodon interaction, the incorrect pairing due to the altered anticodon would lead to misincorporation of amino acids during translation.However, considering the altered tRNA would be only one among many normal tRNAs, its presence may result in a minor proportion of protein molecules with an amino acid sequence variant due to phenylalanine being erroneously inserted where leucine should be.

Such misincorporation might not invariably lead to nonfunctional proteins, especially if the alteration is in a portion of the protein that can tolerate such changes or if protein folding corrects for the missense mutation.