Biochemistry 3 (Tests)

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  • 1/123 Questions

    How many helical turns (the linking number) are found in a relaxed circular DNA of 4500 bp?

    • 500
    • 50
    • 450
    • 350
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  • 2. 

    The linking number of a highly SUPERCOILED plasmid can be readily changed WITHOUT producing a relaxed DNA by:

    • Changing the TEMPERATURE

    • INCREASING the salt concentration

    • The action of TOPOISOMERASE

    • The action of a NUCLEASE such as pancreatic DNAse

    Correct Answer
    A. The action of TOPOISOMERASE
  • 3. 

    In duplex DNA, how many hydrogen bonds does thymine use?

    • 2

    • 3

    • 4

    • 1

    Correct Answer
    A. 2
  • 4. 

    The nucleic acid that is unstable in ACID is

    • DNA

    • MRNA

    • RRNA

    • TRNA

    Correct Answer
    A. DNA
  • 5. 

    A feature which is distinctive to Z-DNA is

    • A LEFT-HANDED helix

    • It has 12 BASES per turn

    • It is found IN VIVO

    • All of the above

    Correct Answer
    A. All of the above
  • 6. 

    Which statement is INCORRECT about eh synthesis of RNA by RNA polymerase in E. coli?

    • A

    • B

    Correct Answer
    A. A
  • 7. 

    Which of the following characteristic IS NOT associated with E. coli PRIMASE

    • It synthesizes the RNA PRIMER in DNA replication

    • It is a SPECIFIC RNA polymerase

    • It is ESSENTIAL for DNA replication

    • It is also a GYRASE

    Correct Answer
    A. It is also a GYRASE
  • 8. 

    A DNA is found to exhibit a melting temperature of 75 C in 0.1 M NaCl.  Under what experimental conditions would the Tm be INCREASED?

    • DECREASING the concentration of DNA

    • INCREASING the concentration of NaCl in the solution

    • ADDING 1% urea (an organic denaturant)

    • All of the above

    Correct Answer
    A. INCREASING the concentration of NaCl in the solution
  • 9. 

    A feature which is distinctive to Z-DNA is

    • A left-handed helix

    • it has 12 bases per turn

    • It is found in vivox

    • All of the above

    Correct Answer
    A. All of the above
  • 10. 

    The polymerase which plays a similar role as that of Prokaryotic Pol III in eukaryotic replication is (pg 1006)

    • DNA polymerase alpha

    • DNA polymerase alpha

    • DNA polymerase delta

    • DNA polymerase alpha

    Correct Answer
    A. DNA polymerase delta
  • 11. 

    When DNA is placed in dilute acid, it gets

    • Depurinated

    • Dephosphorylated

    • Annealed

    • Less active

    Correct Answer
    A. Depurinated
  • 12. 

    The molecule that carries the pure genetic message in eukaryotes is:

    • Antisense DNA

    • MRNA

    • Sense DNA

    • HnRNA

    Correct Answer
    A. MRNA
  • 13. 

    Which item of experimental evidence gives the most support to the conclusion that "Every PURINE BASE pairs with a PYRIMIDINE BASE"

    • % of A = % of G

    • % of C = % of T

    • % of PURINES = % of PYRIMIDINE

    • % of Percent Base Composition in any organism is the same in all cells of the organism and is characteristic of that

    Correct Answer
    A. % of PURINES = % of PYRIMIDINE
  • 14. 

    Which one of the following characteristics IS NOT associated with E. coli PRIMASE?

    • It is essential for DNA replication

    • It synthesizes the RNA primer in DNA replication

    • It is also a gyrase

    • It is a specific RNA polymerase

    Correct Answer
    A. It is also a gyrase
  • 15. 

    If you found a DNA molecule containing URACYL, the most probably CAUSE for it would be:

    • A mutation

    • A MISTAKE by the polymerase

    • A cytosine DEAMINATION

    • A probably ISOLATED RNA

    Correct Answer
    A. A cytosine DEAMINATION
  • 16. 

    The component (s) of DNA which is responsible for the absorbanc band at 250-270 nm is

    • Bases, pentoses, and phosphates all contribute

    • Only bases

    • Only bases and pentoses

    • Only pentoses and phosphates

    Correct Answer
    A. Only bases
  • 17. 

    A strain of E.coli produces the same high level of beta-galactosidase regardless of concentration of lactose in the medium. This strain most likely contains a deltion mutation int he gene (Note: you may assume that deletion mutation causes normal function

    • Lac I

    • Lac 2

    • Gene coding for the gamma-subunit of RNA polymerase

    • Gene encoding the catabolite activator protein

    Correct Answer
    A. Lac I
  • 18. 

    All are true of the DNA double helix EXCEPT:

    • The strands are parallel

    • The strands are held by hydrogen bonds

    • The strands are complementary

    • The strands dissociate with high Urea

    Correct Answer
    A. The strands are parallel
  • 19. 

    The RNA molecules which are involved in PROCESSING the hnRNA are

    • MRNA

    • TRNA

    • RRNA

    • SnRNA

    Correct Answer
    A. SnRNA
  • 20. 

    Why is a primer strand needed in DNA replication?

    • It insures the fidelity of the newly synthesized DNA strand

    • The DNA polymerases require a preexisting strand with a nucleotide having a 3'-OH.

    • The DNA polymerases require a preexisting strand with a nucleotide having a 5'-OH.

    • All of the above are correct

    Correct Answer
    A. The DNA polymerases require a preexisting strand with a nucleotide having a 3'-OH.
  • 21. 

    E. coli replication on the lagging strand (pg 1002)

    • Is primarily carried out by DNA polymerase I

    • Is synthesized continuously

    • This DNA strand is synthesized in a 3'-5' direction of synthesis

    • Is initially synthesized as Okazaki fragments

    Correct Answer
    A. Is initially synthesized as Okazaki fragments
  • 22. 

    In the repair of DNA, the E.coli DNA polymerase involved performs which function in addition to its polymerase activity?

    • It recognizes the abnormality in the duplex DNA structure

    • It removes the damaged section of DNA with its 5'-3' exonuclease activity

    • It nicks DNA to provide a 3'-OH

    • It ligates the DNA after the repair synthesis

    Correct Answer
    A. It removes the damaged section of DNA with its 5'-3' exonuclease activity
  • 23. 

    Which statement is INCORRECT about the STRUCTURE of native E. COLI chromosomal DNA?

    • The DNA is primarily in the BETA-helix

    • The DNA is CIRCULAR and SUPERCOILED

    • The DNA exists as a RIGHT-HANDED double helix

    • The DNA is one large LINEAR piece about 4000 kb in length

    Correct Answer
    A. The DNA is one large LINEAR piece about 4000 kb in length
  • 24. 

    The linking number of a highly supercoiled plasmid can be readily changed without producing a relaxed DNA by

    • Changing the temperature

    • Increasing salt concentration

    • The action of topoisomerase

    • The action of a nuclease such as pancreatic DNAse

    Correct Answer
    A. The action of topoisomerase
  • 25. 

    Which one of the following characteristics ls not associated with E.coli primase?

    • It syntheslzes the RNA primer in DNA repllcation.

    • It is a specific RNA polymerase

    • It is essential for DNA replication

    • It is also a gyrase

    Correct Answer
    A. It is also a gyrase
  • 26. 

    E. coli REPLICATION on the LAGGING strand

    • Is primarily carried out by DNA Polymerase I

    • Is synthesized CONTINUOUSLY

    • This DNA strand is synthesized int he 3'-5' direction of the synthesis

    • Is initially synthesized as OKAZAKI FRAGMENTS

    Correct Answer
    A. Is initially synthesized as OKAZAKI FRAGMENTS
  • 27. 

    DOUBLE-stranded RNA is found in?

    • Ribosomes

    • T-RNA

    • MRNA

    • RNA is NEVER double-stranded

    Correct Answer
    A. RNA is NEVER double-stranded
  • 28. 

    DNA pol III  REPLICATES the LAGGING strand by using

    • A LOOP on the LAGGING strand

    • By READING in the 5'-3' direction

    • By using ONE enzyme per strand

    • By moving BACKWARDS

    Correct Answer
    A. A LOOP on the LAGGING strand
  • 29. 

    In eukaryotic cells, the only RNA molecule which has a poly (A) tail attached to the 3' end is

    • MRNA

    • TRNA

    • SS RNA

    • All rRNA's

    Correct Answer
    A. MRNA
  • 30. 

    A DNA is found to exhibit a melting temperature of 75 degrees Celsius in 0.1M NaCl.  Under what experimental conditions would the Tm be increased? (pg 372)

    • Decreasing the concentration of DNA

    • Increasing the concentration of NaCl in the solution

    • Adding 1% urea (an organic denaturant)

    • All of the above

    Correct Answer
    A. Increasing the concentration of NaCl in the solution
  • 31. 

    The Pribnow box is located

    • At -10 from the ENHANCER ELEMENT

    • At -10 bp from the INITIATION SITE

    • At -35 bp from the OPERATOR

    • At -35 bp from STARTING CODON

    Correct Answer
    A. At -10 bp from the INITIATION SITE
  • 32. 

    The KLENOW fragment of E. Coli DNA Polymerase I can be used to ADD nucleotides to a DNA WITHOUT staggered ends,  IF THE ENDS...

    • Are RECESSED with 5'-phosphates

    • Are RECESSED with 3'-OHs

    • Are EXTENDED with 5'-phosphates

    • Are EXTENDED with 3'-OHs

    Correct Answer
    A. Are RECESSED with 3'-OHs
  • 33. 

    Which IS NOT a property of E. coli DNA Polymerase III?

    • It is responsible for incorporating MOST of the NUCLEOTIDES in the LAGGING strand

    • It synthesizes MOST of the LEADING strand PRIOR to aiding in the synthesis of the LAGGING strand

    • It contains a 3'-5' EXONUCLEASE activity

    • It synthesizes the LEADING strand and the LAGGING strand at the SAME TIME

    Correct Answer
    A. It synthesizes MOST of the LEADING strand PRIOR to aiding in the synthesis of the LAGGING strand
  • 34. 

    In eukaryotes, there are many MORE PROTEINS than GENES.  This can be explained by

    • Association of proteins

    • Multiple subunites

    • Alternative splicing

    • Mutation

    Correct Answer
    A. Alternative splicing
  • 35. 

    What is the primary role of the template strand in DNA replication?

    • It serves as the start point for the new DNA strand

    • It serves as a guide in determining the next nucleotide to be added by the polymerase

    • It increases the processivity of the DNA polymerase

    • It is essential for the 3-5' exonuclease activity

    Correct Answer
    A. It serves as a guide in determining the next nucleotide to be added by the polymerase
  • 36. 

    One of the following is used for protein synthesis:

    • ATP

    • UTP

    • CTT

    • GTP

    Correct Answer
    A. GTP
  • 37. 

    The reason why DNA is stable in BASE and RNA is not is because

    • RNA is single stranded

    • DNA is more basic

    • DNA is complexed with proteins

    • RNA has a 2-OH group

    Correct Answer
    A. RNA has a 2-OH group
  • 38. 

    Telomerase is found in humans in

    • Somatic cells

    • Tumor cells

    • Senescent cells

    • Only found in prokaryotes

    Correct Answer
    A. Tumor cells
  • 39. 

    INCREASE in gene expression in response to a METABOLITE is called:

    • Induction

    • Repression

    • Co-Induction

    • Co-Repression

    Correct Answer
    A. Induction
  • 40. 

    IN THE REPAIR of DNA, the E.coli DNA POLYMERASE involved performs which function IN ADDITION to its polymerase activity?

    • It RECOGNIZES the ABNORMALITY in the duplex DNA structure

    • It NICKS the DNA to provide a 3'-OH

    • It REMOVES the DAMAGED section of DNA with its 5'-3' EXONUCLEASE activity

    • It LIGATES the DNA after the REPAIR synthesis

    Correct Answer
    A. It REMOVES the DAMAGED section of DNA with its 5'-3' EXONUCLEASE activity
  • 41. 

    Which statement is INCORRECT about E. coli DNA Polymerase I?

    • The cells contain MORE MOLECULES of DNA pol I than DNA pol III

    • DNA pol I is a SINGLE POLYPEPTIDE with THREE domains

    • DNA pol I is involved in the REPAIR of UV-damaged DNA

    • DNA pol I has a LARGER TURNOVER number than DNA pol III

    Correct Answer
    A. DNA pol I has a LARGER TURNOVER number than DNA pol III
  • 42. 

    A HELICASE is characterized by:

    • CUTS the DNA and RELIEVES supercoiling

    • It is also a GYRASE

    • UNWINDS DNA without cutting it

    • Needs GTP for energy

    Correct Answer
    A. UNWINDS DNA without cutting it
  • 43. 

    In order to ACTIVATE the catabolite activator protein (CAP), it has to be

    • Phosphorylated

    • CAMP adenylated

    • Glycosilated

    • None of the above

    Correct Answer
    A. CAMP adenylated
  • 44. 

    Why is a primer strand needed in DNA replication?

    • It insures the fidelity of the newly synthesized DNA strand

    • The DNA polymerases require a preexisting strand with a nucleotide having a 5'-OH

    • The DNA polymerases require a preexisting strand with a nucleotide having a 3'-OH

    • All of the above are correct

    Correct Answer
    A. The DNA polymerases require a preexisting strand with a nucleotide having a 3'-OH
  • 45. 

    Which E. coli ENZYME has the GREATEST FREQUENCY of incorporating the INCORRECT NUCLEOTIDE into is nucleic acid POLYMER?

    • RNA polymerase

    • DNA polymerase I

    • DNA polymerase III

    • KLENOW fragment from DNA polymerase I

    Correct Answer
    A. RNA polymerase
  • 46. 

    E. coli DNA polymerase I has all of the following characteristics EXCEPT:

    • A 3'-5' EXONUCLEASE activity

    • A 5'-3' DNA polymerase activity

    • A 5'-3' EXONUCLEASE activity ON A SECOND subunit in the polymerase

    • MODEST processivity (20 nucleotides)

    Correct Answer
    A. A 5'-3' EXONUCLEASE activity ON A SECOND subunit in the polymerase
  • 47. 

    The TUS protein is a type of

    • Gyrase

    • Helicase

    • Primase

    • CONTRAhelicase

    Correct Answer
    A. CONTRAhelicase
  • 48. 

    A GENE is a DNA SEQUENCE that encodes for:

    • A protein

    • RRNA

    • T-RNA

    • All of the above

    Correct Answer
    A. All of the above
  • 49. 

    Which E. coli enzyme has the greatest frequency of incorporating the incorrect nucleotide into its nucleic acid polymer?

    • RNA polymerase

    • DNA polymerase I

    • DNA polymerase III

    • Klenow fragment from DNA polymerase I

    Correct Answer
    A. RNA polymerase

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