Which of the following best explains why the protein sequences of human and mouse GNB1 are identical despite differences in their cDNA sequences?

Question

BlackTom AI · Accepted Answer

Let's evaluate each option step by step to understand why the human and mouse GNB1 protein sequences can be identical even when their cDNA sequences differ.
Option a: The mutation process is guided by intelligent design. This is a metaphysical claim not supported by molecular biology, and it does not explain why identical proteins arise from different DNA sequences.
Option b: Human and mouse GNB1 genes are not truly homologous. If they were not homologous, we would not expect the same protein sequence to arise in both species; in fact, homologous genes in related species often encode similarly functioning proteins, so this option is inconsistent with conserved protein sequences.
Option c: Protein sequences are unaffected by mutations in DNA. In reality, many mutations in DNA do occur, but the genetic code is read in a way that can preserve the amino acid sequence through certain DNA changes, so this blanket statement is false and misleading about how DNA mutations relate to proteins.
Option d: Degenerate (redundant) codons allow different DNA sequences to code for the same amino acid. This is the key concept: multiple codons encode the same amino acid, so synonymous mutations in the DNA can occur without changing the resulting protein sequence, explaining identity of the proteins despite cDNA differences.
Option e: The protein sequences are identical due to random chance. Protein sequences are determined by the genetic code and selective pressures; identical sequences across species are not expected to arise by random chance alone, making this explanation unlikely.
In summary, the only explanation that accounts for identical GNB1 protein sequences despite differing cDNA sequences is the degeneracy of the genetic code, where different DNA sequences can translate to the same amino acids.

CCST9086_1A_2025 Quiz 2

Which of the following best explains why the protein sequences of human and mouse GNB1 are identical despite differences in their cDNA sequences?

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