[Campbell Biology P.396] According to the provided text, which mechanism primarily explains ... | Practice Question

According to the provided text, which mechanism primarily explains how human cells can produce 75,000-100,000 different proteins from approximately 20,000 protein-coding genes?

  • A: Extensive gene duplication and mutation events.
  • B: Alternative RNA splicing, where a single gene can encode multiple polypeptides.
  • C: Extensive post-translational modifications of proteins.
  • D: The existence of multiple ribosomes translating the same mRNA simultaneously.

Explanation

The text explicitly states: 'One important consequence of the presence of introns in genes is that a single gene can encode more than one kind of polypeptide. Many genes are known to give rise to two or more different polypeptides, depending on which segments are treated as exons during RNA processing; this is called alternative RNA splicing.' This mechanism directly explains how a limited number of genes can yield a much larger number of diverse proteins.