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Microbial Genetics
UNIT I
1Which base is found in RNA but not DNA ?
(1) uracil (2) adenine (3) thymine
2In the DNA Double Helix, complementary base pairs are held together by
(1) hydrogen bonds (2) N-glycosidic bonds (3) ionic bonds
3The three pyrimidine bases in DNA are
(1) cytosine,thymine&uracil (2) adenine,guanine &uracil(3) both
4A DNA strand has the sequence A-C-A-G-C-C-G-T-A. What would be its complementary
strand ?
(1) A-C-A-G-C-C-G-T-A (2) U-G-U-C-G-G-C-A-U (3) ) T-G-T-C-G-G-C-A-T
5The DNA molecules of different species differ in their
(1) phosphate backbone (2) sequence of bases (3) type of nucleotides
6The difference between DNA and RNA is
(1) The RNA sugar phosphate backbone contains ribose rather than deoxyribose (2) ) DNA
molecules are double stranded while RNA molecules are single stranded for the most part (3) All
of the above
7The number of hydrogen bonds that hold the Adenine - Thymine base pair together is :
(1) 2 (2) 4 (3) 3
8A nucleoside consists of
(1) a pentose sugar and a oxygen base (2) a pentose sugar and a nitrogeneous heterocyclic
base (3) a hexose sugar and a nitrogeneous heterocyclic base
9The unit within the nucleus that contains a protein complex (located at the center of the unit) of
two H2A, H2B, H3 and H4 histone proteins with DNA wrapped around the complex in two
turns, each turn consisting of about 80 base pairs is called a :
(1) ribosome (2) nucleosome (3) centrosome
10When Hershey and Chase differentially tagged the DNA and proteins of bacteriophages and
allowed them to infect bacteria, what did the viruses transfer to the bacteria?
(1) DNA (2) radioactive phosphorus (3) radioactive sulfur
11Meselson and Stahl proved that
(1) DNA replicates in a semiconservative manner. (2)DNA is the genetic material (3) DNA is
made from nucleotides
12DNA is made up of building blocks called
(1) Proteins (2) bases (3) nucleotides
13In Griffith’s experiments, a harmless variapathogenic when mixed with a heat-killed
pathogenic variant as a result of nt of S. pneumoniae became
(1) transformation (2) conjugation (3) transduction
14Which of the following is correct?
(1) A forms 2 hydrogen bonds with G; T forms 3 hydrogen bonds with C (2) ) A forms 3
hydrogen bonds with T; G forms 2 hydrogen bonds with C (3) ) A forms 2 hydrogen bonds with
T; G forms 3 hydrogen bonds with C
15Which of following RNA characteristically contains unusual purines and pyrimidmes?
(1) tRNA (2) mrna (3) rRNA
16The anticodon is a structure on
(1) tRNA (2) mRNA (3) Snrna
17In RNA, uracil pairs with
(1) adenine (2) thymine (3) cytosine
18RNA instability in alkaline solutions is due to
(1) ribose (2) adenine (3) uracil
19Two features of the tRNA molecule associated, in converting the triplet codon to an amino
acid, are
(1) in the T Loop and D stem and loop (2) in the anticodon loop and D stem loop (3) in the
anticodon loop and the 3' CCA end
20Which of the following is the smallest of the RNAs
(1) Messenger RNA (2) Transfer RNAs (3) Ribosomal RNAs
21The mRNA from which of the following would contain a poly-A tail?
(1) A restriction endonuclease from E. coli (2) Bacterial alpha-amylase (3) Human insulin
22What is the average size (in bp) of a mature t-RNA?
(1) 80 bp (2) 100 bp (3) Both
23What is the function of messenger RNA?
(1) It carries amino acids (2) It is a component of the ribosomes (3) It is a direct copy of a gene
5MARKS
1.
2.
3.
4.
5.
Describe the structure of DNA
Describe the structure and function of tRNA
Give an account on the enzymes involved in DNA replication
Write a critical note on bacterial chromosome
Explain briefly about the transcription in bacteria
8 MARKS
1. Prove that DNA is the genetic material with experimental evidences
2. Discuss in detail the models of DNA replication
UNIT II
Okazaki fragments are used to elongate
(1) the leading strand toward the replication fork (2) the lagging strand toward the replication
fork (3) the lagging strand away from the replication fork
2In replication of DNA, the helix is opened and untwisted by
(1) ribase (2) ligase (3) helicase
3DNA replication is called semiconservative because _______________ of the original duplex
appears in the duplex formed in replication.
(1) none (2) most (3) half
4During DNA replication in prokaryotes, synthesis begins on the circular chromosome
(1) always at the same place (2) at any stretch of DNA that is high in AT pairs (3) randomly on
the chromosome
5DNA replication rates in prokaryotes are approximately of the order of
(1) 10 bases per second (2) 1,00 bases per second (3)1,000 bases per second
6The synthesis of DNA by DNA polymerase occurs in the
(1) 3' to 5' direction (2) 5' to 5' direction (3) 5' to 3' direction
7DNA gyrase is inhibited by
(1) tetracycline (2) nalidixic acid (3) both (a) and (b)
8Which of the following statements on replication in E.coli is correct?
(1) It occurs in a unidirectional manner (2) It occurs in bidirectional manner (3) Always uses T7
DNA polymerase when infected by T7 phage
9In E.coli, which enzyme synthesizes the RNA primer for Okazaki fragments?
(1) DNA A (2) DNA C (3) DNA G
10The rolling circle method of reproduction is used in the reproduction of certain viruses.
(1) True (2) False (3) No
11Each individual zone of a chromosome replicates as a discrete section called
(1) telomere (2) euchromatin (3) replication unit
12_______________ join DNA fragments to the lagging strand.
(1) Ligases (2) Helicases (3) Centromeres
13Which statement about the elongation of the lagging strand during DNA replication is
(1) It is synthesized in a 3' --> 5' direction. (2) It progresses (grows) toward the replication
fork (3) It requires a short RNA primer to proceed.
14During semiconservative replication, the original double helix remains intact and a new
double helix forms.
(1) True (2) False (3) ...
15Experimentation has proven that DNA replicates _____
(1) semiconservatively (2) conservatively (3) dispersively
16DNA is _____ which means that the two template strands of DNA must unwind before they
can separate
(1) displaced (2) lagging (3) plectonemic
17Transient breaks made by _____ enable the strands of DNA to separate in the absence of helix
rotation.
(1) DNA topoisomerases (2) D-loops (3) 5? ? 3? exonucleases
18Which of the following is mismatched?
(1) Semiconservative replication: hybrid of original template plus new polynucleotide
strand (2) Displacement replication: D-loop (3) Linking number: the number of times one strand
crosses the other in a linear molecule
19Which of the following is false regarding rolling circle replication?
(1) The 5? end of the nicked polynucleotides is displaced as the 3? end extends (2) Rolling circle
replication is used to replicate animal mitochondria. (3) The product of rolling circle replication
is linear head-to-tail molecules
20Which of the following is not a characteristic of DNA-dependent DNA polymerases?
(1) The newly synthesized polynucleotide contains deoxyribonucleotide
subunits (2) Polymerization is always in the 5? ? 3? direction. (3) Bacterial DNA polymerase III
possesses 5? ? 3? exonuclease activity
21One of the differences between Type I and Type II topoisomerases is that _____
(1) "Type IA/IIA are linked to the free 5? end of the polynucleotide, while Type IB/IIB are
linked at the 3? end" (2) Type I is present in bacteria but not in eukaryotes(3) bacteria universally
possess Type IB and IIB
22Which molecule serves to destabilize the DNA helix in order to open it up, creating a
replication fork?
(1) DNA gyrase (2) DNA helicase (3) DNA polymerase
23The primer required for DNA synthesis is made by the following enzyme:
(1) DNA polymerase III (2) DNA polymerase I (3) Primase
5 MARK
1.
2.
3.
4.
5.
Differentite somatic and gemetic mutation
Write brief notes on specialized transduction
Describe about the griffth’s transformation experiment
What is meant by nuclease and how endonucleases and exonucleases differ
Write about Hershey and chase experiment
8 MARK
1. Write a detail account on Lac-operon
2. Give a detail account on the effect of mutagenes on nucleotides sequence
UNIT III
The transcribing enzyme is
(1) ligase (2) DNA polymerase (3) RNA polymerase
2Which molecule contains the genetic code?
(1) DNA (2) mRNA (3) tRNA
3Transcription occurs along a ____ template forming an mRNA in the ____ direction.
(1) 5' to 3'; 5' to 3' (2) 5' to 3'; 3' to 5' (3) 3' to 5'; 5' to 3'
4Which of the statements below is false?
(1) The genetic code is overlapping. (2) The genetic code is universal. (3) Degenerate codons
specify the same amino acids.
5The first mRNA codon to specify an amino acid is always
(1) TAC (2) UAA (3) AUG
6The amino acid sequence of a polypeptide chain comprises the ____ structure of the protein.
(1) primary (2) secondary (3) tertiary
7Of the ____ different possible codons, ____ specify amino acids and ____ signal stop.
(1) 20, 17, 3 (2) 180, 20, 60 (3) 64, 61, 3
8RNA contains which bases?
(1) adenine, thymine, guanine, cytosine, uracil (2) adenine, thymine, guanine,
cytosine (3) adenine, guanine, cytosine, uracil
9Which of the following statements is true regarding introns?
(1) Introns are the parts of mRNA that are translated (2)Introns have no function (3) Introns may
be involved in exon shuffling
10Which mode of information transfer usually does not occur?
(1) DNA to DNA (2) DNA to RNA (3) DNA to protein
11A geneticist isolates a gene for a specific trait under study. She also isolates the corresponding
mRNA. Upon comparison, the mRNA is found to contain 1,000 fewer bases than the DNA
sequence. Did the geneticist isolate the wrong DNA?
(1) yes, mRNA is made from a DNA template and should be the same length as the gene
sequence (2) yes, the mRNA should contain more bases than the DNA sequence because bases
flanking the gene are also transcribed (3) no, the final mRNA contains only exons, the introns
were removed
12The effort to decipher the genetic code was led by ____ who was awarded a Nobel Prize for
his work.
(1) Nirenberg (2) Lederberg (3) Watson
13A DNA strand with the sequence AACGTAACG is transcribed. What is the sequence of the
mRNA molecule synthesized?
(1) AACGTAACG (2) UUGCAUUGC (3) AACGUAACG
14What sequence on the template strand of DNA corresponds to the first amino acid inserted
into a protein?
(1) TAC (2) UAA (3) UAG
15Which of the following is an example of the degeneracy of the genetic code?
(1) a given amino acid has more than one codon (2)each codon specifies more than one amino
acid (3) the first two bases specify the amino acid
16The template strand of DNA for one gene may be the coding strand of DNA for another gene.
(1) True (2) False (3)
17Transcription and translation of a gene composed of 30 nucleotides would form a protein
containing no more than ___ amino acids.
(1) 10 (2) 12 (3) 15
18In the absence of tryptophan, the trp repressor is
(1) active and can bind to the operator (2) active and cannot bind to the operator (3) inactive and
cannot bind to the operator
19In the presence of tryptophan, tryptophan binds to the
(1) operator. (2) trp genes. (3) trp repressor
20In the presence of tryptophan, transcription of the trp operon is on
(1) True (2) False (3)
21An operon is a group of genes that is under the control of a singe operator site.
(1) True (2) False (3)
22____ regulate which genes or subsets of genes are transcribed in a particular cell type.
(1) transcription factors (2) chaperone proteins (3) RNA polymerases
23An antibiotic interferes with the ability of the ribosome to move. What affect would exposure
to this chemical have on a bacterial cell?
(1) protein synthesis will be affected (2) the protein synthesized will be shorter than
normal (3) no proteins will be produced
5 MARKS
1.
2.
3.
4.
5.
Write about the enzymes involved in transcription
Describe about SOS repair
Explain how do ultraviolet ray cause mutations in microorganisms
Write briefly about Fluctuation Test.
Describe the experimental detection covalently close circles of DNA
8 MARKS
1. Explain the process of bacterial conjugation
2. Discuss the process of transformation with experimental evidences.
UNIT IV
1
The mutation which will not affect the length of a protein is,
(1) nonsense mutation (2) missense mutation (3)frameshift mutation
2
Changes in which of the following characterizes mutations?
(1) Phenotype (2) Genotype (3) Both (a) and (b)
3
Which of the following(s) is/are steps in excision repair mechanisms?
(1) Excision (2) Incision (3) All of these
4
Which of the following mutations arise without exposure to external agents?
(1) Spontaneous mutations (2) Analogous mutations (3)Induced mutations
5
Due to which of the following DNA repair mechanisms, one is able to distinguish newly
synthesized DNA strands from older one?
(1) New strands do not contain cytosine bases (2) New strands are lower in molecular
size (3) Old strands are methylated while new strands are not
6
A nonsense mutation may result into
(1) an abnormal elongation of a polypeptide (2) a large deletion within the reading frame of
a gene (3) a premature termination of the synthesis of a polypeptide
7
Which of the following mutation affects only a single nucleotide?
(1) Aerial mutation (2) Site mutation (3) Point mutation
8
When mutations involve vital functions so that the mutants are nonviable, it is a
(1) nonsense mutation (2) lethal mutation (3) none of these
9
A mutagen is defined as
(1) an enzyme that repairs mutations (2) a chemical or physical agent that induces
mutations (3) an inhibitor of gene modification
A nonsense mutation introduced into the DNA sequence of a gene may
10 (1) cause premature termination of the mRNA (2) shorten the length of the protein encoded
by the gene (3) have no effect on the transcript or protein made
11
Which of these mechanisms for thymine dimers repair lead to mutations?
(1) Excision repair (2) SOS repair (3) Never leads to mutation
12
Frame shift mutation may occur as a result of
(1) formation of a thymine-dimer (2) deamination of cytosine to uracil (3) none of the above
13
Thymine dimers are directly repaired with the help of visible light by process known as
(1) phosphorylation (2) excision repair (3)Photoreactivation
14
Which of the following bacterial genome was sequenced first?
(1) E. coli (2) S. pneumoniae (3) H. influenzae
15
which of the following biomolecule has self repair mechanisms
(1) DNA,RNA & Protein (2) DNA & RNA (3) DNA only
16
which of the following chemicals induce depurination
(1) methyl ethane sulphonate (2) nitrosoguanidine (3) all of these
which of the following mechanism of DNA polymerase helps in preventing error during
17 DNA replication
(1) rechecking (2) proof checking (3) proof reading
18
The proteins involved in mismatch repair are
(1) MutS (2) MutH (3) all of these
19
which of the following dimer formation is most common
(1) thymidine dimer (2) cytidine dimer (3) both a and b
20
Dimer repair mechanism
(1) excision repair (2) recombinational repair (3) all of these
Thymine dimer are often corrected by light induced repair mechanism.The enzyme involved
21 inn the process is
(1) Photolyase (2) photoligase (3) DNA glycosylase
22
which of the following is dark repair
(1) nucleotide excision repair (2) base excision repair (3)both a and b
Recombinational repair is often due to
(1) incorporation of many incorrect nucleotides by DNA polymerase (2) many cytidine
23
dimer and associated large gaps in a strand (3) many thymidine dimer formation and
associated large gaps in a strand
24
DNA glycosylase is an enzyme involved in base excision repair.The function is
(1) addition of correct base (2) addition of correct nucleotide(3) removal of incorrect base
25
DNA repair mechanism is absent in
(1) nuclear genome (2) mitochondrial genome (3)chloroplast genome
5 MARKS
1.
2.
3.
4.
5.
Describe about excision repair
Give an account on spontaneous mutation
Write an account of back mutation
Explain the phage mediated genetic recombination in bacteria
Draw and explain the structure of Trna
8MARKS
1. Define mutation write an account of different kind of mutation encounted in bacteria
2. Write briefly on the methods used for producing auxotrophic mutants in bacteria
UNIT V
1. The transfer of genetic material between bacteria in direct physical contact is called
(1) conjugation (2) transformation (3) transduction
2. The transfer of a naked fragment of DNA between bacteria is called
(1) conjugation (2) transformation (3) transduction
3. The transport of bacterial DNA to other bacteria via bacteriaphages is called
(1) conjugation (2) transformation (3) transduction
4. This type of recombination commonly occurs between a pair of homologous DNA sequences
(1) general recombination (2) site-specific recombination (3) replicative recombination
5. This type of recombination does not require homologous sequences and is important for the
integration of viral genomes into bacterial chromosomes
(1) general recombination (2) site-specific recombination (3) replicative recombination
6. This type of recombination does not require homologous sequences and is utilized by mobile
genetic elements that move about chromosomes
(1) general recombination (2) site-specific recombination (3) replicative recombination
7. Horizontal transfer can best be described as:
(1) the transmission of genetic information from parent to offspring (2) the transmission of
genetic information from one independent, mature organism to another (3) the synthesis of RNA
from a DNA template
8. Plasmids can best be described as:
(1) small, circular DNA molecules that can exist independently of chromosomes commonly
found in bacteria (2) a complex membrane structure that covers the chromosome of bacteria (3)
another name for a chloroplast
9. The name of the process in which plasmids can be eliminated from a cell is:
(1) fixing (2) breaking (3) curing
10. F factor plasmids play a major role in what bacterial process?
(1) transduction (2) replication (3) conjugation
11. This type of plasmid carries genes encoding enzymes that degrade substances such as
aromatic compounds, pesticides or sugar
(1) metabolic plasmid (2) virulence plasmid (3) F factors
12. Mobile genetic elements that carry the genes required for integration into host chromosomes
(1) plasmids (2) transposons (3) replicon
13. The tranposase gene encodes an enzyme that
(1) facilitates general recombination (2) facilitates viral replication within a genome (3)
facilitates site-specific integration of transposable elements.
14. Composite transposons are formed when
(1) an IS element integrates into a plasmid (2) a small deletion occurs in the transposase gene of
an IS element (3) two IS elements integrate into a chromosome with only a small distance
between separating them
15. Which of the following are true in regards to F+ x F- mating events?
(1) DNA is transferred from F+ to F- cells (2) DNA is transferred from F- to F+ cells (3) o DNA
is transferred because F- cells are unable to perform conjugation
16. A bacterial cell that is able to take up naked DNA is said to be
(1) competent (2) liable (3) infected
17. The relationship between a virus and host where no new viral particles are produces and the
viral genome is replicated along with host chromosome
(1) lysogeny (2) lysis (3) transformation
18. Interrupted mating experiments are used to determine what information?
(1) DNA nucleotide sequences (2) levels of DNA homology (3) bacterial genome maps
19. Which of the following can be used as a tool by microbial genetisists?
(1) plasmids (2) bacteriophage (3) all of the above
20. In which type of transduction does the transducing particle carry only specific portions of the
bacterial genome?
(1) general transduction (2) abortive transduction (3) specialized transduction
21. Recombination of virus genomes occurs
(1) by transformation (2) by transduction (3) when two viruses with homologous chromosomes
infect a host cell simultaneously
22. These are bacterial proteins that destroy other bacteria
(1) viruses (2) transposable elements (3) bacteriocins
23. A replicon is
(1) a DNA molecule that is able to replicate and be maintained (2) the enzyme responsible for
transposition (3) DNA molecule that encodes pili for conjugation
24. The type of recombination that commonly occurs between a pair of homologous DNA
sequences is,
(1) general recombination (2) replicative recombination (3) site-specific recombination
5 MARKS
1. Discuss in detail about protein synthesis in prokaryotes
2. Write about the structure of bacteri chromosome and how the genes arranged on the
bacterial chromosome
3. What are the different type of mutation discuss any two of them in detail
4. Write an essay on conjugation in bacteria
5. Explain in detail about the structure and type of bacterial transposons
8 MARKS
1. Define competence in relation to transformation. How do you differentiate between
natural and artificial transformation occurring in bacteria
2. Draw a scheme for making the cell of Escherichia coli to be competent and for taking up
foreign DNA for transformation