Exam 3 answers

1. Why did Hershey and Chase use 35S (radioactive sulfur) in a study of bacteriophage T2 reproduction?
*(a) to label the protein and show that it remained outside the cell
(b) to show that RNA was the hereditary molecule
(c) to label the DNA and show that it remained outside the cell
(d) because it labeled the hereditary molecule of the bacterium but not the phage
(e) because it labeled the material that converted nonpathogenic bacteria into pathogenic bacteria

2. A western blot
(a) uses DNA polymerase to make many copies of DNA.
*(b) uses antibodies to identify a protein of interest.
(c) uses restriction fragment length polymorphisms (RFLPs) to identify different alleles.
(d) can be used to match DNA found at a crime scene with that of a suspect.
(e) is used to identify bacterial colonies in gene cloning.

3. In Jacob and Monod's classic experiment on gene regulation in bacteria
(a) the properties of exon splicing were discovered.
(b) histones were found to activate genes.
(c) growth factor receptors were found to act on ras.
*(d) presence of allolactose caused a repressor to be pulled off of the operator.
(e) transposons were found to mutate the gene.

4. Which of the following diseases is thought to be mediated by a protein (devoid of all nucleic acids) called a prion?
(a) smallpox
(b) AIDS
(c) flu
*(d) mad cow disease
(e) pneumonia

5. Capsids would be found
(a) on antibody molecules.
(b) on the RNA primer needed for DNA replication.
(c) in bacterial cells.
(d) right next to RNA polymerase.
*(e) on a virus.

6. The genetic code, with codons such as UGG, applies to
(a) the actions of DNA polymerase.
*(b) translation.
(c) the control of the gene's promoter.
(d) the nucleotide sequence of the tail that is added to the mRNA molecule.
(e) the replication fork.

7. Which of the following is true about the lac operon?
(a) It only occurs in eukaryotes.
(b) It explains the manufacture of DNA from virus RNA.
(c) It explains how a virus organizes the synthesis of its protein coat.
(d) It explains how the DNA polymerase action is primed.
*(e) The mRNA codes for three enzymes.

8. A thymine dimer is
(a) one of the comon DNA binding motifs of a transcription factor.
(b) a portion of the mRNA molecule.
*(c) DNA damage for which there is a repair mechanism.
(d) one way one strand of DNA reproduces a whole new strand.
(e) the membrane receptor for a growth factor.

9. Restriction fragment length polymorphisms (RFLPs) can be used
(a) for the PCR reaction.
(b) to suppress tumors.
*(c) in mapping genes.
(d) to inject "good" genes in gene therapy.
(e) to identify clones carrying recombinant plasmids.

10. Why is ampicillin resistance useful in biotechnology?
*(a) Only clones containing recombinant plasmids survive.
(b) It allows the normal allele to be incorporated into the patient's chromosome in gene therapy.
(c) There is no need to add new polymerase after each heating.
(d) It is used to map gene positions without using a genetic trait as a marker.
(e) It is used as a probe in DNA hybridization.

11. A histone is a
(a) transcription factor.
(b) promoter.
*(c) protein associated with DNA.
(d) protein associated with RNA
(e) portion of the final, processed, mRNA molecule.

12. Across from the sense strand of DNA is
(a) DNA from the other homologue from the other parent.
(b) cDNA (complementary DNA).
(c) mRNA with the introns spliced out.
*(d) a DNA strand with A across from T, T across from A, C across from G, and G across from C.
(e) the promoter.

13. The amino acid valine has 4 codons: GUU, GUC, GUA and GUG. What is the name for the aspect of the code that allows differences in the third position?
(a) leucine zipper
(b) reverse transcription
(c) exon splicing
(d) conjugation
*(e) degeneracy

14. Changing the codon for one amino acid to a stop codon is a
(a) base-pair insertion
(b) base-pair deletion
(c) missense mutation
*(d) nonsense mutation
(e) transposon insertion

15. A protooncogene
(a) is the name for a gene cloned into a bacterium.
*(b) a gene that, if mutated, leads to cancer.
(c) causes the spongiform encephalitis diseases.
(d) is the official word for a "jumping gene."
(e) is the special kind of gene that makes so many different kinds of antibodies.

16. Okazaki fragments are
*(a) pieces of DNA on lagging strand DNA replication.
(b) the enzyme used for production of cDNA from mRNA.
(c) the place around the origin of replication where the DNA strands are separated.
(d) the tail on the final mRNA molecule.
(e) the portions removed from the pre-mRNA to make mRNA.

17. An exon is
*(a) a part of the pre-mRNA (and the eukaryotic gene) that codes for the protein.
(b) a circle of DNA that is in a bacterium but that is not part of the bacterial chromosome.
(c) a nucleosome (one of the "beads on a string") seen on a DNA double helix.
(d) a viral protein.
(e) a replication fork in the DNA.

18. Where would you find an anticodon?
(a) on the antisense DNA strand
(b) on the intron
(c) on cDNA
*(d) on tRNA
(e) in a retrovirus

19. Sickle-cell anemia
*(a) is a missense mutation.
(b) is a nonsense mutation.
(c) is a mutation in the DNA that does not change the amino acid sequence.
(d) is a one base-pair insertion.
(e) is caused by alternate splicing.

20. Inverted repeats are characteristic of
*(a) transposons.
(b) introns.
(c) prions.
(d) enhancers.
(e) restriction fragments.

21. In one DNA double helix,
(a) one strand comes from your mother and the other from your father.
(b) either of the two strands can be used for transcription of a specific gene.
(c) one strand is completely "useless" in the sense that its nucleotide sequence is not related in any way with amino acid sequence.
*(d) only one strand is the sense strand for a given gene.
(e) only one strand is used as the template for the DNA synthesis for the daughter cells.

22. A plasmid is
(a) a part of the coat of a virus.
(b) a receptor tyrosine kinase.
(c) an enhancer (distal control element).
(d) what you make with PCR.
*(e) a piece of DNA in a bacterium.

23. What kind of cell makes an antibody?
(a) bacterium
(b) virus
*(c) B lymphocyte
(d) Every cell in your body makes antibodies.
(e) a carcinoma cell

24. One use of autoradiography is to
(a) construct a genomic DNA library.
*(b) use a radioactive DNA probe to identify a cloned gene
(c) cut DNA in a way to make staggered sticky ends.
(d) make cDNA.
(e) amplify a gene if you know the N- and C-terminal protein sequences.

25. The molecule most specific to keeping the ends of chromosomes intact is
(a) restriction enzyme
(b) RNA polymerase
*(c) telomerase
(d) polymerase from Thermus aquaticus
(e) amino acyl tRNA

26. Hybridization is the term used to describe
(a) the ability for an abnormal protein in Creutzfeld-Jacob Syndrome in humans and scrapie in sheep to alter the normal protein.
*(b) the tendency for DNA to stick to a complementary strand.
(c) the ability of a helix-turn-helix motif to bind DNA.
(d) the ability of bacteria to exchange DNA in a way that resembles mating.
(e) the ability for a gene to go into bone marrow cells in gene therapy.

27. A growth factor
*(a) stimulates a membrane protein that phosphorylates the amino acid tyrosine.
(b) is a type of RNA.
(c) is an enzyme that makes a new DNA strand grow along a template.
(d) is associated with the growth of the polypeptide chain at the level of the ribosome.
(e) binds to DNA upstream of the coding sequence.

28. A zinc finger is
(a) an oncogene.
*(b) a common type of DNA binding domain of a transcription factor.
(c) a transposon.
(d) a receptor for a growth factor.
(e) an infectious protein.

29. The ribosome reads the mRNA until
(a) it reaches the 5' cap.
(b) it reaches the TATA box.
*(c) it reaches any one of the following three codons: UAG, UAA or UGA.
(d) it reaches an anticodon.
(e) it reaches a transcription factor.

30. How come there can be antibodies to cope with so many antigens?
(a) Alternate splicing of mRNA handles that.
*(b) There can be rearrangement of DNA segments.
(c) There are separate genes in the genome for every antibody made.
(d) The antibodies come from the microbes themselves.
(e) There can't; that's why you need vaccines to confer active immunity.

31. Analogy -- Box : Domain ::
(a) cytoplasm : nucleus
(b) pre-mRNA : mRNA
(c) translation : transcription
*(d) DNA : protein
(e) intron : exon

32. What is essential to making cDNA?
(a) Southern blotting
(b) restriction endonucleases
(c) plasmids
(d) antibiotics
*(e) reverse transcriptase

33. Following classic work by Griffith in 1928, Avery and his coworkers announced in 1944 what transormed non-pathogenic bacteria into bacteria that caused pneumonia in mice. What was it?
(a) bacteriophage
(b) transposons
(c) retrovirus
(d) protein
*(e) DNA

34. Which is not part of the final mRNA?
(a) exons
(b) 5' cap
(c) poly-A tail
(d) bases A, U, C and G
*(e) introns

35. What is NOT true about the antibody molecule?
(a) It is a tetramer.
(b) It has constant and variable regions.
(c) Chains are connected by disulfide ( -S-S- ) bridges.
(d) Overall it is Y-shaped.
*(e) It is sometimes called "p53."

This page was last updated 11/12/01

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