12._______ is to transcription as _______  are to translation.
(A) RNA spliceosome； ribosomes
(B) RNA polymerase； ribosomes
(C) Primer, ribozymes
(D) DNA polymerase； RNA polymerase
(E) DNA polymerase； ribozymes

8. How is a gradient of H+ ions formed across the inner mitochondrial membrane? (A) The electron transport chain uses energy from transfer of an electron donated by NADH to pump H across the inner mitochondrial membrane against its electrochemical gradient. (B) ATP synthase generates a H+ gradient across the inner mitochondrial membrane. (C) Electrons move fom NADH to a chain of proteins with lower electronegativities. (D) The electron transport chain uses ATP to pump Ht across the inner mitochondria membrane against its electrochemical gradient. (E) The electron transport chain of proteins contains pores that are leaky to H+.

9. When a cell secretes a growth factor that binds to receptors on its own membrane preventing it from proliferating, this is an example of _______. (A) direct intercellular signaling (B) endocrine signaling (C) contact-dependent signaling (D) paracrine signaling (E) autocrine signaling

10. The monomers of DNA and RNA are (A) monosaccharides. (B) nucleotides. (C) bases (D) nucleic acids. (E) pentoses.

11. Why does a DNA strand grow only in the 5' to 3' direction? (A) because DNA polymerases can only add nucleotides to the 3' end of the growing molecule (B) because DNA polymerases can only add nucleotides to the 5' end of the growing molecule (C) because the DNA molecule only unwinds in the 5' to 3' direction (D) because DNA polymerase requires the addition of a starter nucleotide at the 5' end (E) because the 5'-end is capped

13. Which sequence of events CORRECTLY describes the initiation and elongation steps of translation in prokaryotic cells?(1) initiator tRNA binds start codon on mRNA(2) small ribosomal subunit binds to mRNA(3) large ribosomal subunit binds(4) tRNA entry and peptidyl transfer reaction(5) translocation of ribosome and release of tRNA(A) 1,2,3,4,5(B) 1,2,3,5,4(C) 1,3,2,4,5(D) 2,3,1,5,4(E) 2,1,3,4,5

14. Genes organized into an operon are beneficial to certain bacteria because the operon allows for (A) differential regulation of individual genes that encode proteins with a common function. (B) coordinated regulation of a group of genes that encode proteins with a common function. (C) separate regulation of individual genes that encode proteins with different functions. (D) coordinated regulation of a group of genes that encode proteins with different functions. (E) coordinated regulation of a group of proteins involved in numerous cellular activities.

15. DNA methylation (A) increases transcription. (B) inhibits transcription. (C) increases crossover events. (D) decreases crossover events. (E) increases post-translational modification of proteins.

16. A researcher determined that a strain of E. coli is producing a shortened version of a protein required for glucose metabolism. What type of mutation could be responsible for this shorter than normal protein? (A) nonsense mutation (B) missense mutation (C) silent mutation (D) sense mutation (E) frameshift mutation

17.________ can convert proto-oncogenes into oncogenes. (A) Gene amplifications (B) Retroviral insertions (C) Chromosomal translocations (D) Missense mutations (E) All of these choices are correct

18. Which of the following is NOT a checkpoint that controls the progression of the cell cycle? (A) Cyclins and cyclin-dependent kinases are proteins that are responsible for advancing a cell through the phases of the cell cycle. (B) The G2 checkpoint checks for DNA damage and determines if all of the DNA is replicated. (C) The metaphase checkpoint determines if all chromosomes are attached to the spindle apparatus. (D) Cytokinesis involves the formation of cleavage furrow to separate the cells. (E) The restriction point determines if conditions are favorable for cell division and if the DNA is undamaged.