Multiple Choice: There are 25 questions each worth 4 points for a total of 100 points. There is just one answer for each question. Use a number 2 pencil to completely fill in the answer of your choice. Remember to also fill in your SS# and name on the Scantron sheet. Remember to fill in your LAST NAME FIRST.
 
 

1. Which of the following is the correct answer?
 
 

a) The exon-intron splice junction is a sequence of bases in the DNA that involves recognition of A-T rich regions by snRNP's

b) snRNP's contain DNA as well as RNA

c) The lariat structure forms a 3'---5' phosphodiester linkage between the 5' end guanine residue and an internal adenine residue of the intron. Shortly after, the intron is spliced out of the message

d) The spliceosome complex uses ribozymes to cut introns from Hn RNA
 
 

2. Which of the following is the correct answer?
 
 

a) rRNA 's have a 5' cap

b) rRNA's have a poly A tail at their 3' end

c) The 60s ribosomal subunit is composed of a 28s, 18s, 5.8s, and 5s rRNA's plus proteins

d) The 30s ribosomal subunit is made up of the 16s rRNA and proteins
 
 

3. During the translation event,
 
 

a) RF1 recognizes the stop signals UAA and AAG

b) RF2 recognizes the stop signals UAA and UGA

c) ssb, helicases and gyrases are involved

d) mRNA is being translated as it is being transcribed in eucaryotic cells
 
 

4. Which of the following is the correct statement?

a) The length of the leader sequence can determine the number of times a gene is transcribed in procaryotic cells

b) The sigma factor is very important in prokaryotic cells for finding the AUG codon for initiating the translation event

c) It is believed that the 5' cap is important for terminating the translation event in eucaryotic cells

d) The 5' cap of eucaryotic cells has an unusual 2'--5' phosphodiester linkage between the guanine residue and the first base of the mRNA
 
 

5. Which of the following is the correct statement?
 
 

a) The recognition of the first AUG on mRNA as a start signal for translation in procaryotes is essentially carried out by IF 1

b) IF 3 brings a charged tRNA and places it in the A site of the ribosomal complex

c) tRNA^trp describes a tRNA molecule that is specifically charged with the amino acid tryptophan

d) An amino-acyl transferase activates a specific amino acid and charges a specific tRNA with this activated amino acid
 
 

6. Which of the following statements is the correct one?
 
 

a) Factor EF-Tu + GTP attaches onto charged tRNA's and places them into the A site in the ribosomal complex

b) The initiating AUG codon is first placed into the A site of the initiating complex

c) Factor EF-Ts + GTP moves the ribosomal complex over onto the next codon during the elongation step of translation

d) EF-G + GTP attaches onto f-met-tRNA and places it into the P site of the ribosomal complex
 
 

7. If transcription occurred in a 3'--->5' direction and if you initially placed alpha-labeled ³²P-NTP's in the reaction mix and then switched to non-labeled NTP's after a few seconds, the transcribed product would have
 
 

a) no label in the RNA

b) label only at the 5' end of the RNA P-P-P-ribose-base

c) label only at the 3' end of the transcript OH

d) label at both ends of the transcript
 
 

8. If transcription occurred in a 3'--->5' direction and if you initially placed gamma-labeled ³²P-NTP's in the reaction mix and then switched to non-labeled NTP's after a few seconds, the transcribed product would have
 
 

a) no label in the RNA

b) label only at the 5' end of the RNA

c) label only at the 3' end of the RNA

d) label at both ends of the RNA
 
 

9. Following the experimental protocol in question 7 and since RNA is really transcribed in a 5'--->3' direction, the transcribed product would have
 
 

a) no label in the RNA

b) label only at the 5' end of the RNA

c) label only at the 3' end of the RNA

d) label at both ends of the RNA
 
 

10. Which of the following is the correct statement?
 
 

a) RNA pol III synthesizes tRNA in procaryotic cells

b) The core enzyme in E. coli cells recognizes the CAAT sequence and allows RNA polymerase to melt into the DNA at the Pribnow Box sequence

c) RNA pol III synthesizes snRNA's in eucaryotic cells

d) RNA pol II synthesizes 5.8s rRNA in eucaryotic cells
 
 

11. Suppose you infected E. coli cells with a strain of phage lambda and suppose also that lysogeny has taken in the bacterial cells. What would you think would happen if these lysogenized cells were then reinfected with the same strain of phage lamda? Would the E. coli cells

a) lyse

b) not lyse

c) can't say because not enough information is given

d) none of the above
 
 
 
 

*****UNLESS OTHERWISE NOTED, ASSUME GLUCOSE IS NOT PRESENT IN THE MEDIUM for QUESTIONS 12, 13, 14, and 18
 
 

12. Which of the following is the correct answer?
 
 

a) In the E. coli cell, there is always a small amount of the z, y and a gene transcripts present

b) A mutation of the i gene to the i^- condition would allow transcription of the z, y and a genes even when glucose were present in the medium

c) If lactose and glucose were present in the medium at the same time, the arabinose operon would be induced if arabinose were also to be added to the medium

d) When the lac operon is turned on , the E. coli cell will begin to synthesize lactose from glucose
 
 

13. Suppose the condition of the E. coli cell was i^- o^c z y a where the z, y, a genes are normal.
 
 

a) The lac operon can be induced only when lactose is added to the medium

b) The z,y, a genes will be transcribed even when glucose is added to the medium

c) The i gene mutation will over-ride the o mutation and prevent the transcription of the z, y, a genes

d) Even in the absence of lactose, the z, y, a genes will be transcribed
 
 
 
 
 
 

14. If the condition of the E. coli cell was i^- o⁺ z⁺ y^- / i⁺ o^c z^- y⁺,
 
 

a) lactose will not be utilized as a carbon and energy source if it is placed in the medium

b) the mutant o gene allows the cell to constitutively synthesize functional galactosidase even in the absence of lactose

c) it will appear as if an induction event occurred when lactose is added to the medium

d) no lactose will be allowed into the cell because one of the y genes is mutated
 
 

15. If glucose is present in the medium containing a culture of E. coli cells,
 
 

a) adenyl cyclase will be inhibited

b) cAMP phosphodiesterase will be inhibited

c) the trp operon will be shut down, even though the concentration of trytophan is low

d) the lac operon will be induced if lactose is also added to the medium
 
 

16. Which of the following is the correct statement?
 
 

a) The light chain has more possibilities of gene rearrangement than the heavy chain

b) Both the heavy and light chains have J segments in their gene arrangements

c) the number of possible gene rearrangements for antibody diversity in humans is about 50 trillion

d) RNA splicing of introns does not take place after the RNA is transcribed from its antibody gene
 
 

17. Which if the following is the correct statement?
 
 

a) IgG is the antibody found in excretory fluids

b) Tc cells are the main target cells for HIV infection

c) T4 cells are denoted as the antigen presenting cells

d) A T4 cell recognizes a B cell that is capable of producing a specific antibody and stimulates it with interleukin 2 to begin antibody production
 
 

18. Regarding the arabinose operon,

a) when there is no arabinose in the medium, the Ara C protein binds only to the ara I gene and prevents the transcription of the B,A,D genes

b) in the presence of arabinose, the Ara C protein binds with arabinose and binds to both the ara I gene and the o site

c) in the absence of arabinose in the medium, the Ara C protein binds to both the ara I gene and the o site thus effectively shutting down transcription of the B,A,D genes

d) in the presence of arabinose and glucose in the medium, cAMP is at a high level and arabinose will induce the arabinose operon to turn itself "on"
 
 

19. Regarding the trp operon,
 
 

a) the amino acid tryptophan acts as the sole repressor of this operon

b) the trp R gene synthesizes an active repressor that, alone, binds to the o site and effectively shuts down transcription

c) suppose a deletion mutation took place in the attenuator region of the trp operon DNA such that only the two trp codons (UGG) were removed from the leader sequence of the mRNA. Assume that all the other codons are still in phase. If this happened, the trp operon would shut itself down even if there were no tryptophan in the cell

d) if glucose is added to the medium, the trp operon would get shut down due to catabolite repression
 
 

20. Which of the following is the correct answer regarding phage lambda gene regulation?
 
 

a) The N gene produces an anti-termination protein that overcomes the strong transcription stop signal, tr₃

b) The amount of CI repressor protein is kept at low or at maintenance levels because transcription of mRNA for CI repressor protein from P_m makes a very short leader sequence and the RNA polymerase easily falls off

c) Cro protein is essential for the lysogenic event

d) CI protein allows the E. coli cell to become lysed
 
 

21. During phage lambda infection of E. coli cells,
 
 

a) CI protein first binds to OR₁ and then to OR₂ to shut down the transcription of late genes

b) the CII and CIII proteins combine with Cro protein to establish the lytic phase of phage lamda infection

c) Cro protein first binds to OR₃ to inhibit the transcription of the late genes

d) P_E is the promotor for the transcription of late genes in the lytic phase of phage lambda infection
 
 

22. Which of the following is the correct answer?
 
 

a) v-onc genes have introns

b) protooncogenes have introns

c) cyclins are proteins that add phosphate residues to proteins

d) cyclins are dependent on kinases in order to phosphorylate proteins
 
 

23. Which of the following is the correct answer?
 
 

a) The p53 protein is a CDK kinase

b) Dephosphorylated pRB is the active form and it binds with E2F which is a transcription factor and this binding inactivates E2F

c) The binding of pRB to E2F allows the cell cycle to proceed from G1 to the S phase

d) The Wilm's tumor gene only causes cancer in adults
 
 

24. Which of the following is the correct answer?
 
 

a) The Wilm's tumor gene is a protooncogene- that is it is a gene that promotes cell division

b) The Wilm's tumor gene synthesizes zinc finger proteins that act as transcription factors

c) In the normal fetal kidney, the Wilm's tumor gene normally causes the cells to proliferate rapidly for a short period of time

d) The zinc finger protein produced by the Wilm's tumor gene has a leucine zipper that is the active site of the protein
 
 

25. Which of the following is the correct answer?
 
 

a) The ras gene synthesizes a kinase

b) A point mutation in the ras protooncogene causes the ras protein to lose its GTPase activity

c) The p53 gene is a protooncogene in that in normal cells it induces cells to divide

d) The normal p53 protein stops the cell cycle at G2 just before the mitotic event in order that the cell may dissolve the nuclear membrane and allow the chromosomes to begin condensing thus readying the cell for mitosis