34. Which of the following descriptions regarding cDNA libraries is correct?

(1) The production of cDNA requires use of reverse transcriptase. 

(2) cDNA contain intronic sequences.

(3) cDNA libraries are enriched in protein-coding genes. 

(4) cDNA libraries are cell-type specific.
(A) (1) and (2)
(B) (1), (3), and (4)
(C) (1) only
(D) (2), (3), and (4)
(E) All of the descriptions are correct.

30. The 2024 Nobel Prize in Physiology or Medicine was awarded to Victor Ambros and Gary Ruvkun for discovering microRNA and its role in post-transcriptional gene regulation. Which statement is incorrect? (A) Lin-4 was the first microRNA to be discovered by Victor Ambros's team. (B) Victor Ambros's team found that lin-4 negatively regulates LIN-14 protein expression. (C) Gary Ruvkun's team found the 5'UTR of lin-14 mRNA is required for lin-4 inhibition. (D) In C . elegans, the microRNA lin-4 critically regulates developmental timing (E) Most microRNAs are conserved across species.

31. There is no codon for the amino acid hydroxyproline, but this amino acid is a prominent feature of collagen structure. Which of the following is a likely explanation? (A) Hydroxyproline is substituted for proline after translation by a cut and patch mechanism. (B) Proline is covalently modified to give hydroxyproline after translation. (C) There is an alternative mechanism for synthesis of proteins that contain hydroxyproline. (D) All of above are likely explanations. (E) It is not possible to form a hypothesis from the information given.

32. One of the hopes for use of recent knowledge gained about non-coding RNAs lies with the possibilities for their use in medicine. Of the following scenarios for future research, which would you expect to gain most from RNAs? (A) Exploring a way to turn on the expression of pseudogenes. (B) Targeting siRNAs to disable the expression of an allele associated with autosomal recessive disease. (C) Targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease. (D) Creating knock-out organisms that can be useful for pharmaceutical drug design. (E) Looking for a way to prevent viral DNA from causing infection in humans.

33. Which of the following statement regarding bacterial artificial chromosomes (BACs) is correct? (A) BACs are generally not stable. (B) BACs are present in high copy numbers per cell. (C) BACs are derived from the E. coli chromosome. (D) BACs can maintain DNA sequences of hundreds of thousands of nucleotide pairs. (E) All of the above.

35. Which of the following descriptions regarding the electrical properties of cellular membranes is correct? (A) If the membrane is impermeable to an ion, the membrane potential approaches the equilibrium potential for that ion. (B) The resting potential in most animal cells is between 20 mV and 120 mV (positive inside). (C) Setting up (or changing) the membrane potential requires changing the bulk concentrations of the ions on the two sides of the membrane. (D) The resting potential decays immediately following the inhibition of the Na+-K+ pump by a drug. (E) None of the above.

36. Which of the following accurately describes the role of Ran-GTP in the directionality of nuclear transport? (A) Ran-GTP is hydrolyzed to Ran-GDP in the cytoplasm, releasing cargo from exportins. (B) The Ran-GTP gradient, maintained by RanGEF in the nucleus and RanGAP in the cytoplasm, ensures unidirectional cargo transport. (C) Ran-GTP directly phosphorylates nuclear transport receptors to facilitate cargo import and export. (D) Ran-GTP binds importin in the cytoplasm to prevent premature cargo release. (E) Ran-GTP hydrolysis occurs exclusively within the nuclear pore complex to control bidirectional movement.

37. Which of the following best explains how proteasomal and lysosomal degradation differ in substrate specificity and regulation? (A) Both systems rely on molecular chaperones, but only lysosomes degrade non-protein cellular components such as lipids. (B) Lysosomes selectively degrade misfolded proteins through autophagy, while proteasomes degrade native proteins marked for turnover. (C) Proteasomes degrade extracellular and cytosolic proteins, while lysosomes are restricted to extracellular material. (D) Proteasomal activity is regulated by lysosomal enzymes, ensuring coordinated protein turnover. (E) Proteasomal degradation requires substrate ubiquitination and ATP hydrolysis, while lysosomal degradation is ubiquitin-independent and primarily pH-dependent.

38. Control of gene expression by Ca2+ can occur through which of the following mechanism? (1) Changes in the transactivating properties of transcription factors following the activation of -dependent kinases.  (2) Changes in the transactivating properties of transcription factors following the activation of -dependent phosphatases.  (3) Translocation of the C-terminal fragment of an L-type channel to the nucleus where it binds to a nuclear transcription factor. (A) (1) (B) (2) (C) (3) (D) All of above are correct (E) None of above is correct

39. The term "synapse" has been used to describe the contact points between: (1) neuronal cells. (2) immune cells. (3) epithelial cells. (A) (1) (B) (2) (C) (3) (D) None of above (E) All of the above

40. Which of the following statement about myelination is incorrect? (A) Myelination is required in both the CNS (central nervous system) and PNS (peripheral nervous system). (B) Myelination involves the ensheathment and insulation of axons by radial glial cell membranes. (C) Myelinating Schwann cells extend their processes to wrap up axons at a 1:1 relationship. (D) Myelinating Oligodendrocytes extend multiple processes that will contact and myelinate several axons. (E) None of above is incorrect.