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Multiple choice question for engineering

Set 1

1. Which of the following involves remarkable capacity of short segment of DNA to move from one place to another?
a) DNA transposition
b) DNA replication
c) Translation
d) Transcription

View Answer

Answer: a [Reason:] A short segment of DNA with the remarkable capacity to move from one location in a chromosome to another.

2. Which of the following process occurs between DNA molecules of very similar sequences?
a) Homologous genetic recombination
b) Site specific recombination
c) Non-homologous recombination
d) Replicative recombination

View Answer

Answer: a [Reason:] Non-homologous recombination occurs in regions where no large –scale sequence similarity is apparent. Site-specific recombination occurs between particular short sequences present on otherwise dissimilar parental molecules. Replicative recombination generates a new copy of the transposable element at a new location of DNA.

3. Which of the following process occurs in regions where no large –scale sequence similarity is apparent?
a) Homologous genetic recombination
b) Site specific recombination
c) Non-homologous recombination
d) Replicative recombination

View Answer

Answer: c [Reason:] Site-specific recombination occurs between particular short sequences present on otherwise dissimilar parental molecules. Replicative recombination generates a new copy of the transposable element at a new location of DNA. Homologous genetic recombination occurs between DNA molecules of very similar sequences.

4. Which of the following process generates a new copy of the transposable element at a new location of DNA?
a) Homologous genetic recombination
b) Site specific recombination
c) Non-homologous recombination
d) Replicative recombination

View Answer

Answer: d [Reason:] Homologous genetic recombination occurs between DNA molecules of very similar sequences. Site-specific recombination occurs between particular short sequences present on otherwise dissimilar parental molecules. Non-homologous recombination occurs in regions where no large –scale sequence similarity is apparent.

5. Which of the following occurs between particular short sequences present on otherwise dissimilar parental molecules?
a) Homologous genetic recombination
b) Site specific recombination
c) Non-homologous recombination
d) Replicative recombination

View Answer

Answer: b [Reason:] Homologous genetic recombination occurs between DNA molecules of very similar sequences. Non-homologous recombination occurs in regions where no large –scale sequence similarity is apparent. Replicative recombination generates a new copy of the transposable element at a new location of DNA.

6. Which of the following promotes branch migration at higher rates than does Rec-A?
a) Rec-B
b) Rec-C
c) Rec-D
d) Ruv-A and Ruv-B

View Answer

Answer: d [Reason:] Ruv-A and Ruv-B proteins form a complex that binds to Holliday intermediates, displays Rec-A protein and promotes branch migration at higher rates than does Rec-A.

7. Which of the following is called a resolvase?
a) Ruv-C
b) Ruv-A
c) Ruv-B
d) Rec-A

View Answer

Answer: a [Reason:] Nucleases that specifically cleave Holliday intermediates are often called resolvases, the Ruv-C protein is one of at least two such nucleases in E. coli.

8. Which of the following does not code for an enzyme having both helicase and nuclease activity?
a) Rec-A
b) Rec-B
c) Rec-C
d) Rec-D

View Answer

Answer: a [Reason:] In E. coli, rec-B, rec-C and rec-D genes encode the Rec-BCD enzyme, which has both helicase and nuclease activities.

9. The sequences of the recombination sites recognized by site-specific recombinases are
a) Partially asymmetric
b) Partially symmetric
c) Symmetric
d) Palindromic

View Answer

Answer: a [Reason:] The sequences of the recombination sites recognized by site-specific recombinases are partially asymmetric (non-palindromic).

10. Which of the following contain only the sequences required for transposition and the genes for proteins that promote the process?
a) Insertion sequences
b) Complex transposons
c) Transposons
d) Chromosomes

View Answer

Answer: a [Reason:] Complex transposons contain one or more genes in addition to those needed for transposition.

Set 2

1. If the mutation has a negligible effect on the function of a gene, it is known as a
a) Silent mutation
b) Frame shift mutation
c) Substitution mutation
d) Insertion mutation

View Answer

Answer: a [Reason:] Mutations can involve the replacement of one base pair with another (substitution mutation) or the addition or deletion of one or more base pairs (insertion or deletion mutations).

2. Which of the following mechanisms will remove uracil and incorporate the correct base?
a) Direct repair
b) Base excision repair
c) Mismatch repair
d) Nucleotide excision repair

View Answer

Answer: b [Reason:] Base excision repair is responsible for removing small, non-helix-distorting base lesions from genome.

3. Which of the following has the self-repairing mechanisms?
a) DNA and RNA
b) DNA, RNA and protein
c) Only DNA
d) DNA and proteins

View Answer

Answer: c [Reason:] Only DNA has the self-repairing mechanism.

4. The function of enzyme involved in base excision repair is
a) Addition of correct base
b) Addition of correct nucleotide
c) Removal of incorrect base
d) Removal of phosphodiester bond

View Answer

Answer: c [Reason:] DNA glycosylases are responsible for the removal of incorrect base in base excision repair.

5. The DNA polymerase involved in base excision repair is
a) DNA polymerase α
b) DNA polymerase β
c) DNA polymerase σ
d) DNA polymerase γ

View Answer

Answer: b [Reason:] DNA polymerase β is involved in base excision repair.

6. An alteration in a nucleotide sequence that changes a triplet coding for an amino acid into a termination codon is
a) Nonsense mutation
b) Mutagenesis
c) Mutation
d) Mutagen

View Answer

Answer: a [Reason:] Nonsense mutation (point mutation) results in a premature stop codon.

7. A point mutation that replaces a purine with another purine, or a pyrimidine with another pyramidine
a) Nonsense mutation
b) Silent mutation
c) Transition mutation
d) Transversion

View Answer

Answer: c [Reason:] Nonsense mutation (point mutation) results in a premature stop codon. Transversion refers to substitution of a purine for a pyrimidine or vice-versa. If the mutation has a negligible effect on the function of a gene, it is known as a silent mutation.

8. The enzyme of E.coli is a nuclease that initiates the repair of double stranded DNA breaks by homologous recombination
a) DNA glycosylase
b) DNA ligase
c) DNA polymerase
d) RNA polymerase

View Answer

Answer: a [Reason:] DNA glycosylase catalyzes the first step of base excision repair in DNA.

9. Recombinational repair is often due to
a) Incorporation of many incorrect nucleotides by DNA pol
b) Many cystidine dimer and associated large gaps in a strand
c) Many thymidine dimer formation and associated large gaps in a strand
d) All of these

View Answer

Answer: c [Reason:] Recombinational repair is often due to many thymidine dimer formations and associated large gaps in a strand.

10. The enzyme photolyase is used in what method of repair?
a) Base excision
b) Photo reactivation
c) Nucleotide excision
d) None of these

View Answer

Answer: b [Reason:] They repair the damage caused by exposure to ultraviolet light. It is used in photo reactivation mechanism.

Set 3

1. A codon contains how many nucleotides
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: c [Reason:] A codon is a triplet of nucleotides that codes for a specific amino acid.

2. The initiation codon is
a) AUG
b) UAA
c) UAG
d) UGA

View Answer

Answer: a [Reason:] UAA, UAG and UGA are termination codons.

3. The termination codon is not
a) AUG
b) UAA
c) UAG
d) UGA

View Answer

Answer: a [Reason:] AUG is an initiation codon.

4. How many t-RNAs are required to translate all 61 codons?
a) 31
b) 32
c) 30
d) 29

View Answer

Answer: b [Reason:] A minimum of 32 t-RNAs are required to translate all 61 codons.

5. Which position of a codon is said to wobble?
a) First
b) Second
c) Third
d) Fourth

View Answer

Answer: c [Reason:] The third position in each codon is much less specific than the first and second and is said to wobble.

6. In which of the following cases the first base of anticodon pairs with only one codon?
a) When the first base of anticodon is A or C
b) When the first base of anticodon is A or G
c) When the first base of anticodon is inosine
d) When the first base of anticodon is G or U

View Answer

Answer: a [Reason:] When the first base of the anticodon is C or A, base pairing is specific and only one codon is recognized by that t-RNA.

7. In which of the following cases the first base of anticodon pairs with two codons?
a) When the first base of anticodon is A or C
b) When the first base of anticodon is A or G
c) When the first base of anticodon is inosine
d) When the first base of anticodon is G or U

View Answer

Answer: d [Reason:] When the first base of the anticodon is G or U, base pairing is less specific and two different codons may be read.

8. In which of the following cases the first base of anticodon pairs with three codons?
a) When the first base of anticodon is A or C
b) When the first base of anticodon is A or G
c) When the first base of anticodon is inosine
d) When the first base of anticodon is G or U

View Answer

Answer: c [Reason:] When inosine is the first nucleotide of an anticodon, three different codons can be recognized.

9. The genetic code translated the language of
a) Proteins into that of RNA
b) Amino acids into that of RNA
c) RNA into that of proteins
d) RNA into that of DNA

View Answer

Answer: c [Reason:] The overall process of mRNA-guided protein synthesis is often referred to simply as translation.

10. Wobble hypothesis was first proposed by
a) Nirenberg
b) Watson and Crick
c) Watson
d) Crick

View Answer

Answer: d [Reason:] Crick proposed a set of four relationships called the wobble hypothesis.

Set 4

1. CAP is
a) Catabolite gene activator protein
b) Catabolite gene repressor protein
c) Anabolite gene activator protein
d) Anabolite gene repressor protein

View Answer

Answer: a [Reason:] cAMP receptor protein or CRP is sometimes called CAP, catabolite gene activator protein.

2. Trp repressor is a
a) Homodimer
b) Homotrimer
c) Heterodimer
d) Heterotrimer

View Answer

Answer: a [Reason:] Trp repressor is formed by two identical molecules, each subunit containing 107 amino acid residues.

3. Attenuator sequences base-pair to form a stem-and-loop structure rich in
a) A = T
b) G ≡ C
c) A = C
d) G = C

View Answer

Answer: b [Reason:] Attenuator sequences base-pair to form a G≡C rich stem-and-loop structure closely followed by a series of U residues.

4. Which of the following regulatory sequence allows transcription to continue?
a) Sequence 1
b) Sequence 2
c) Sequence 3
d) Sequence 4

View Answer

Answer: b [Reason:] Regulatory sequence 1 is crucial for a tryptophan sensitive mechanism. Sequence 2 is an alternative complement for sequence 3. Sequence 4 is for attenuating transcription.

5. Formation of the attenuator stem-and-loop structure depends on the events that occur during translation of
a) Regulatory sequence 1
b) Regulatory sequence 2
c) Regulatory sequence 3
d) Regulatory sequence 4

View Answer

Answer: a [Reason:] Formation of the attenuator stem-and-loop structure depends on the events that occur during translation of regulatory sequence 1, which encodes a leader peptide.

6. Which of the following takes place when tryptophan levels are low?
a) Ribosomes quickly translates sequence 1
b) Sequence 2 is blocked before sequence 3 is transcribed
c) Ribosomes pauses at the Try codons in sequence 1
d) Attenuation at the attenuator structure formed by sequences of 3 and 4

View Answer

Answer: c [Reason:] a, b and d take place when tryptophan levels are high.

7. Which of the following takes place when tryptophan levels are high?
a) Attenuation at the attenuator structure formed by sequences of 3 and 4
b) Ribosomes pauses at the Try codons in sequence 1
c) Formation of paired structure between 2 and 3 sequences prevents attenuation
d) 2:3 structures, unlike the 3:4 attenuator, does not prevent transcription

View Answer

Answer: a [Reason:] b, c and d take place when tryptophan levels are low.

8. Whose interaction with Lex-A facilitates the repressor’s self-cleavage reaction?
a) Rec-A
b) Rec-B
c) Rec-C
d) Rec-D

View Answer

Answer: a [Reason:] This type of function of Rec-A is called co-protease activity.

9. When DNA segment is in one orientation
a) The gene for FljB and gene encoding FljA are expressed
b) The gene for FliC are expressed
c) The gene for FljB and gene encoding FljA are not expressed
d) The gene for FljB and gene encoding FljC are not expressed

View Answer

Answer: a Expression: When DNA segment is in one orientation, the gene for FljB and gene encoding FljA are expressed; the repressor shuts down expression of the gene for FliC.

10. Which of the following encodes recombinase?
a) fliC
b) fljB
c) hin
d) fljA

View Answer

Answer: c [Reason:] The hin gene encodes the recombinase that catalyzes the inversion of the DNA segment containing fljB promoter and the hin gene.

Set 5

1. Which of the following is not an example of housekeeping genes?
a) RNA polymerase
b) r-RNA genes
c) Beta galactosidase
d) Enzymes required for basic metabolic pathways common to most cells

View Answer

Answer: c [Reason:] Enzymes required for basic metabolic pathways common to most cells are housekeeping genes; RNA polymerase and r-RNA genes are the examples.

2. Lactose utilization by E. coli requires
a) Lac-Z
b) Lac-A
c) Lac-Y
d) Lac-l

View Answer

Answer: c [Reason:] Lactose utilization by E. coli requires lac-Y.

3. The lactose repressor is encoded by
a) Lac-l
b) Lac-A
c) Lac-Y
d) Lac-Z

View Answer

Answer: a [Reason:] Lac-l encodes lactose repressor.

4. Where does a repressor bind an operon?
a) Operator
b) Promoter
c) Inducer
d) Catabolite activator site

View Answer

Answer: a [Reason:] Repressor binds an operon at operator.

5. Lac repressor dissociates from its operator when the repressor binds to
a) Heat shock module
b) Promoter
c) Inducer
d) Catabolite activator site

View Answer

Answer: c [Reason:] The Lac repressor dissociates from its operator when the repressor binds to its inducer, allolactose.

6. The lac repressor has which of the following DNA-binding motif?
a) Helix-turn-helix
b) Zinc finger
c) Homeodomain
d) Leucine zipper

View Answer

Answer: a [Reason:] The lac repressor has helix-turn-helix DNA-binding motif.

7. Which of the following are the structural motifs that mediate protein-protein interactions?
a) Leucine zipper and basic helix-loop-helix
b) Homeodomain
c) Zinc finger
d) Helix-turn-helix

View Answer

Answer: a [Reason:] Regulatory proteins contain domains not only for DNA binding but also for protein-protein interactions. Homeodomain, zinc finger and helix-turn-helix are DNA-binding domains.

8. If lactose and glucose are provided in the growth medium of a culture of E. coli
a) Lactose operon is not transcribed
b) Lactose metabolism is favored
c) Both lactose and glucose are metabolized at same rate
d) Adenylate cyclase is activated

View Answer

Answer: a [Reason:] If lactose and glucose are provided in the growth medium of a culture of E. coli lactose operon is not transcribed.

9. Which of the following is not required for the expression of genes in the lactose operon?
a) lacl gene product
b) cAMP
c) Allolactose
d) Adenylate cyclase

View Answer

Answer: a [Reason:] cAMP, allolactose and adenylate cyclase are required for the expression of genes in the lactose operon.

10. Which out of the following is not an example of inducible operon?
a) Lactose operon
b) Galactose operon
c) Maltose operon
d) Tryptophan operon

View Answer

Answer: d [Reason:] Lactose operon, galactose operon and maltose operon are the examples of inducible operon.