[Campbell Biology P.471] Which of the following accurately describes a challenge encountered... | Practice Question

Which of the following accurately describes a challenge encountered when attempting to express a complex eukaryotic gene e.g., a mammalian gene with introns that requires post-translational glycosylation in a bacterial host cell, and a common solution to overcome one of these challenges?

  • A: Challenge: Bacterial cells lack the machinery for RNA splicing to remove introns. Solution: Use complementary DNA (cDNA) which only includes exons.
  • B: Challenge: Bacterial cells cannot perform post-translational modifications like glycosylation. Solution: Introduce additional genes into bacteria to synthesize glycosylation enzymes.
  • C: Challenge: Eukaryotic promoters are not recognized by bacterial RNA polymerase. Solution: Use a different bacterial species as the host.
  • D: Challenge: Eukaryotic proteins are toxic to bacterial cells. Solution: Express the protein in smaller, non-toxic fragments.

Explanation

The text explicitly states two main challenges for expressing eukaryotic genes in bacteria: 1 promoter incompatibility, which is solved by using an expression vector with a strong bacterial promoter, and 2 the presence of noncoding regions introns in most eukaryotic genes. Bacterial cells lack the RNA-splicing machinery to remove introns, which would prevent correct expression. The common solution is to use complementary DNA cDNA , which is synthesized from mRNA and thus contains only the exons coding regions . Additionally, the text mentions that bacterial cells cannot perform post-translational modifications like glycosylation due to lacking membrane-bound organelles, making eukaryotic host cells often more suitable for such genes.