[Campbell Biology P.395] Eukaryotic genes often have long noncoding stretches called introns... | Practice Question

Eukaryotic genes often have long noncoding stretches called introns. Which of the following best explains why these introns are transcribed into pre-mRNA but then removed before translation?

  • A: Introns contain regulatory sequences essential for guiding the ribosome during protein synthesis.
  • B: Removing introns allows for the creation of a continuous coding sequence from discontinuous gene segments, which is necessary for proper protein translation.
  • C: Introns prevent the degradation of pre-mRNA in the nucleus, ensuring its stability until translation.
  • D: Introns serve as templates for the synthesis of small RNAs involved in other cellular processes, separate from protein coding.

Explanation

The text explicitly states: 'The noncoding segments of nucleic acid that lie between coding regions are called intervening sequences, or introns.' It further explains that 'In the process of RNA splicing, the introns are cut out from the molecule and the exons joined together, forming an mRNA molecule with a continuous coding sequence.' This process ensures that only the coding segments exons are translated into protein.