Biochemistry MCQ Quiz Hub

1. The binding of lac repressor to DNA could be considered to be analogous to.
competitive inhibition of an enzyme
mixed-type inhibition of an enzyme
uncompetitive inhibition of an enzyme
allosteric effects in enzyme regulation

2. Rho-dependent termination of transcription in E. coli
requires ATP
requires about 50 nucleotides of uncomplexed mRNA
both (a) and (b)
removes mRNA and holoenzyme from the DNA

3. Enhancers are regions that
bind RNA polymerase
are adjacent to the TATA box
are CAT box binding proteins
modulate transcription

4. Transcription by E. coli polymerase occurs in
four phases known as initiation, propagation, elongation and termination
three phases known as initiation, elongation and termination
two phases known as initiation and termination
none of the above

5. Which of the following is necessary for transcription to occur?
DNA molecule
RNA polymerase
DNA polymerase
Both DNA & RNA polymerase

6. Multiple copies of 5S genes, located at a chromosomal site distinct from the other rRNA genes
are transcribed by rRNA polymerase III and the 5S rRNA
are transcribed by rRNA polymerase II
are transcribed by rRNA polymerase I and the 5S rRNA
are transcribed by DNA polymerase I

7. Each tRNA molecule has a cloverleaf secondary structure consisting of
three stem loops
two stem loops
four stem loops
either (a) or (b)

8. What is a promoter?
A specific sequence of DNA to which a catabolic repressor binds
A specific sequence of DNA to which RNA polymerase binds
A specific DNA sequence to which a restriction endonuclease binds
None of the above

9. The function of the sigma factor of RNA polymerase is to
assure that transcription begins at the proper point
assure that transcription ends at the proper point
assure that translation begins at the proper point
assure that translation ends at the proper point

10. In both eukaryotes and prokaryotes, a promoter region that is rich in AT bases is called as
CATT
Shine Dalgarno region
TATA box
SV40 region

11. The RNA polymerases that transcribe bacterial DNA are
multisubunit enzymes
only active inside the cell
interchangable with DNA polymerases
highly glycosylated in their active forms

12. Immediately after transcription
a methylated guanine cap is added to the 51 end of the transcript
a methylated guanine cap is added to the 31 end of the transcript
both (a) and (b)
a poly adenylation signal is added

13. Transcription factors are
promoters
proteins which bind to DNA and regulate transcription
TATA boxes
CATT boxes

14. The major function of RNA polymerase's sigma factor is
recognition of the translational stop sequence
recognition of the transcriptional start sequence
recognition of the transcriptional stop sequence
recognition of the translational start sequence

15. Most transcripts of protein coding genes are cleaved
at the 3' end just after a poly adenylation signal
at the 3' end just before a poly adenylation signal
at the 5' end immediately after a poly adenylation signal
at the 5' end immediately before a poly adenylation signal

16. RNA is synthesized on a DNA template in a process called __________ , which utilizes the enzyme __________
translation, RNA polymerase
transcription, DNA polymerase
transcription, RNA polymerase
replication, DNA polymerase

17. The closed complex at bacterial promoters is
in equilibrium with free RNA polymerase and the promoter
not affected by promoter mutations
bound more tightly when repressors are present
not affected by activator proteins

18. Transcription begins
at the start codon
upstream from the start codon
downstream from the start codon
none of these

19. Transcription results in
an amino acid chain
messenger RNA
complementary DNA
Okazaki fragments

20. RNA polymerase holoenzyme initiates transcription which involves
recognition of the -10 sequence and -35 sequence
recognition of the -10 sequence only
recognition of the -35 sequence only
none of the above

21. The transcriptional regulatory proteins in eukaryotes which induce transcription usually have
at least two distinct domains of protein structure, a DNA binding domain and an activation domain
at least two distinct domains of protein structure and a DNA binding domain
at least one distinct domains of protein structure, a DNA binding domain and an activation domain
none of these

22. In prokaryotes, transcription is
terminated by the stop codon
terminated by a protein called rho
terminated by a poly A sequence
terminated by a start codon

23. In eukaryotes, there are three different RNA polymerases. The RNA polymerase responsible for transcription of mRNA is
RNA polymerase I
. RNA polymerase II
RNA polymerase III
none of these

24. The nucleons of eukaryotic cell has
RNA polymerase I
RNA polymerase II
RNA polymerase III
all of these

25. Upstream regions which are essential for correct transcription are called
enhancers
start codons
promoters
transcription factors

26. Transcription of each set of rRNA genes by RNA polymerasel produces
a single 45S rRNA precursor molecule
a single 5S rRNA precursor molecule
a single 18S rRNA precursor molecule
a single 28S rRNA precursor molecule

27. The regions of a gene located at -10 and -35, with respect to the start of transcription, are termed
start codons.
oriC regions.
Shine Dalgarno sequences.
promoters.

28. Which of the following conditions would cause the release of the lac repressor protein from the lac operator site on DNA?
Presence of glucose in the growth media
Presence of lactose in the growth media
Presence of IPTG (isopropyl thiogalactoside) in the growth media
Both (b) and (c)

29. Beta pleated sheets are examples of protein's
primary structure
secondary structure
tertiary structure
quaternary structure

30. BRACl, an inherited form of breast cancer, regulates cell division by
binding to a DNA sequence
complexing with cyclins
binding to the cell outer membrane
binding to the protein RAD 51 which repairs DNA damage

31. Metastasis involves
ability of cells to dissolve cellular matrix
metalloprotein levels
decreased levels of proteins that regulate metalloproteins
all of the above

32. Signal sequences are part of a protein that
signal folding of the protein
signal the protein synthesis on the ribosomes is ended
transport proteins to other sites within the cell
refold proteins in prion-associated diseases

33. Individuals with PKU disease are mentally retarded unless
phenylalanine in the diet is restricted
tyrosine in the diet is restricted
homogentisic acid in the diet is restricted
none of the above

34. Marfan's syndrome is thought to be a mutation affecting
hemoglobin synthesis
collagen synthesis
metabolism of homogentisic acid
insufficient thyroid production

35. Cyclins are proteins that
regulate ability of cells to invade tissue
regulate passage from one stage of cell division to another
regulate apoptosis of damaged cells
none of the above

36. Over 50% of common cancers are associated with damage to a protein, p53. This protein
is a cyclin
is a tumor supressor
is an oncogene
regulates apoptosis

37. Protein folding is
automatic, mediated by the protein itself
mediated by other proteins called chaperones
mediated by the ribosomes
none of the above

38. Sickle cell disease is due to
a mutation in the beta chain of Hb
a mutation in the alpha chain of Hb
infection with a parasite
none of the above

39. The four subunits of the hemoglobin (Hb) gene represent protein's
primary structure
secondary structure
tertiary structure
quaternary structure

40. A mutation in the tip binding site of the repressor would result in
constitutive trp operon expression
inducible trp operon expression
no operon expression
none of the above

41. The first protein complex to bind to the TATA box is
transcription factor IIA
transcription factor IIB
transcription factor IID
all of these

42. Which of the following is not part of the lac operon?
I
O
P
none of these

43. The lac operon is transcribed in which segments?
1
2
3
4

44. A frameshift mutation occurs in the sigma subunit gene transcribed as part of SPOl early genes. What will be the immediate result?
Early genes will not be translated
Middle genes will not be transcribed
The bacterial host will lyse immediately
Infection will proceed as usual

45. In the presence of high levels of tryptophan
attenuator allows transcription of trp structural genes
attenuator propogates transcription
attenuator terminates transcription
none of the above

46. Tubulin is regulated by
binding of tubulin to tubulin mRNA
splicing of the tubulin transcript
binding of tubulin to the tubulin translational product
binding of tubulin to DNA

47. Transcription factors are
regions of DNA in the promoter area
regions of DNA in the enhancer area
any protein which binds to DNA
proteins which bind DNAand initiate transcription

48. Genes which need to be coordinately regulated but are not in operons may be regulated by
common transcription factor binding domains
TATA boxes
CAAT regions
GC regions

49. What are genes?
The functional unit of inheritance
A fragment of DNA
A portion of a chromosome
All of the above

50. Which of the following is not a transcription factor?
Helix-turn-helix proteins
Zinc finger proteins
Leucine zipper proteins
Steroid hormones

51. Enhancers differ from promoters in that
they initiate transcription
they are adjacent to the start codon
their orientation can be inverted without effect
they are restricted to a specific gene

52. Methylated gene are
active
silent
dynamic
either (a) or (b)

53. Which of the following occur in the presence of glucose?
lac Z gene expression is increased
cAMP increases
Binding of CAP-cAMP complex to the promoter area decreases
none of the above

54. Sex hormones activate transcription of specific genes by
binding to a transcription factor
binding to RNA polymerase
binding to DNA enhancer region
binding to DNA promoter region

55. The lac operon is translated into __________ proteins.
1
2
3
4

56. In the presence of tryptophan in the cell, the repressor is __________
bound to tryptophan
bound to DNA
bound to both DNA and tryptophan
bound to neither tryptophan nor DNA

57. Catabolite activating protein exerts __________ control on transcription of the lac operon genes.
positive
negative
may be positive or negative
none of these

58. DNA is methylated at
AC sequences
TATA sequences
CAAT sequences
CG sequences

59. Why are several structural genes regulated as a unit in bacteria?
An accident of evolution
It allows coordinating regulation of genes with a common function
The bacteria chromosome is so small; many different genes must be controlled by the same promoter
none of the above

60. Alternate splicing of RNA transcripts is a mechanism to regulate
tubulin
tachykinins
DNA methylation
leucine zippers

61. The viruses that can achieve neoplastic transformation are called
DNA tumor viruses
RNA tumor viruses
retroviruses HIV
none of these

62. For gene transfer to be effective, transforming DNA must be.
incorporated into the bacterial chromosome
incorporated into a viral genome
free in the bacterial cytoplasm
none of the above

63. Double stranded DNA denaturation with specified limit of temperature is
reversible reaction
irreversible reaction
either (a) or (b)
none of these

64. From a single molecule of DNA, PCR can make
one additional copy
hundreds of copies
thousands of copies
millions of copies

65. Genomic libraries are made from
genomic DNA of an organism
genomic RNA of an organism
genomic cDNA of an organism
genomic mRNA of an organism

66. Bacteriophages are
cells in the blood that eat bacteria
a class of bacteria
bacterial viruses
none of the above

67. Specialized transduction occurs when
the bacteriophage incorporates randomly in the bacterial chromosome
the bacteriophage never incorporates into the bacterial chromosome
the bacteriophage always incorporates at the same position in the bacterial chromosome
none of the above

68. PCR is used
to diagnose genetic diseases
to solve crimes
to study gene function
all of these

69. To clone into a plasmid vector, both the plasmid and the foreign DNA are cut
with the same restriction enzyme and mixed together
with different restriction enzyme and mixed together
with the combination of enzymes and then seperated
with the combination of enzymes and mixed together