This set of Vector Biology Question Bank focuses on “Bacteriophages – 2”.
1. What is the function of a tail of the head-and-tail lambda phage?
a) Stabilization of phage DNA
b) Attachment of phage
c) Release of replicative enzymes
d) Helps in motility
Explanation: The DNA is contained in the polyhedral head structure and the tail serves to attach the phage to the bacterial surface and to inject the DNA into the cell.
2. How are genes arranged in a lysogenic phage (for example a lambda phage)?
b) In clusters
c) On opposite ends
d) Similar genes at distant positions
Explanation: Genes related in terms of function are clustered together in the genome. Clustering is profoundly important for controlling the expression of the lambda genome as it allows genes to be switched on and off rather than individually.
3. Circularization of the injected linear phage DNA molecule is facilitated by which of the following?
a) Polyhedral head
b) Cos sites
c) Phage tail
d) Capsid proteins
Explanation: The lambda cohesive ends are called the cos sites and they play different roles during the infection cycle. They allow the linear DNA molecule that is injected into the cell to be circularized, which is a necessary prerequisite for insertion into the bacterial genome.
4. By which mechanism does the replication of new lambda DNA molecules are produced in the host bacterium?
a) Rolling Circle Mechanism
b) DNA Polymerase Binding
c) The same mechanism as that of host
d) Replication fork propagation
Explanation: A large number of new lambda DNA molecules are produced by the rolling circle mechanism of replication, in which a continuous DNA strand is rolled off the template molecule.
5. M13 filamentous phage DNA molecule is smaller than the head-and-tail lambda phage.
Explanation: M13 DNA molecule is much smaller than the lambda DNA molecule, being only 6407 nucleotides in length. It is circular and consists entirely of single stranded DNA.
6. Which of these is not a feature associated with M13 phage?
a) Doesn’t need genes for insertion into host genome
b) Capsid constructed of multiple copies of 3 genes
c) Simpler infection cycle than lambda
d) Capsid constructed of 15 different proteins
Explanation: The small size of M13 DNA molecule means that it has a room for fewer genes and this is possible because the M13 capsid is constructed from multiple copies of just 3 proteins (3 genes) whereas synthesis of lambda phage capsid involves 15 different proteins.
7. How does an injection of a filamentous phage (example- M13) DNA into the host bacterium occur?
a) Via pilus
b) Surface attachment
Explanation: Injection of an M13 DNA molecule into an E.coli occurs via pilus, the structure that connects two cells during sexual conjugation. Once inside the cell, single stranded molecule acts as the template for synthesis of the complementary strand.
8. Replicative form (RF) refers to what part of the M13 bacteriophage?
a) M13 genome
b) Restriction sites
c) Endonuclease activity
d) Replication phase
Explanation: The double-stranded form of M13 genome is known as the Replicative form, which behaves much like a plasmid; this is what makes it an attractive cloning vector.
9. Phage display technique makes use of which of the following vectors?
c) 2 micron circle
Explanation: M13 vectors are used for phage display, a technique for identifying genes whose protein products interact with one another. M13 is also used in DNA sequencing and in vitro mutagenesis.
10. Which of the following is a positive regulatory gene on the lambda phage genome?
Explanation: Except for the two positive regulatory genes N and Q, all functionally related genes are clustered together on the phage lambda genome map.
Sanfoundry Global Education & Learning Series – Vector Biology & Gene Manipulation.
To practice Vector Biology Question Bank, here is complete set of 1000+ Multiple Choice Questions and Answers.