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Interview MCQ Set 1

1. Which of the following zones have considerable rooted vegetation?
a) littoral zone
b) limnetic zone
c) profundal zone
d) benthic zone

View Answer

Answer: a [Reason:] There is usually a fairly large littoral zone along the shore which has considerable rooted vegetation and includes regions where light penetrates to the bottom.

2. Which of the following layer is composed of soft mud or ooze?
a) Photic zone
b) Limnetic zone
c) Benthic zone
d) Profundal zone

View Answer

Answer: c [Reason:] The benthic region is composed of soft mud or ooze at the bottom.Profundal region exists at much greater depths of the water body whereas littoral zone is present along the shore.

3. In which of the following seasons does the nutrient concentration falls at a drastically lower level?
a) Winter
b) Spring
c) Summer
d) Autumn

View Answer

Answer: c [Reason:] Occurrence of algal blooms during the spring and autumn results in lowering the nutrient concentration during summers.

4. Rapidly expanding urbanization makes it difficult to generalize upon typical microbial flora of streams.
a) True
b) False

View Answer

Answer: a [Reason:] The drastic environmental changes in streams and rivers created by rapidly expanding urbanization on the one hand and changes in farming practices on the other make it impossible to generalize upon typical or characteristic microbial flora.

5. The coastal adjunct of the marine ecosystem is __________________
a) stream
b) estuary
c) river
d) lake

View Answer

Answer: b [Reason:] An estuary is the coastal adjunct of the marine ecosystem. It is a semi-enclosed coastal body of water which has a free connection with the open sea.

6. The Chesapeake Bay, one of the world’s major estuarine system serves as the receiving basin for how many rivers?
a) 4
b) 6
c) 3
d) 9

View Answer

Answer: d [Reason:] The Chesapeake Bay, one of the world’s major estuarine system serves as the receiving basin for nine major rivers, draining much of southern New York State,Pennsylvania, Maryland and Virginia.

7. In regions of the estuary that are nutritionally poor, it is more likely to find which of the following organisms?
a) coliforms
b) appendaged bacteria
c) viruses
d) fecal streptococci

View Answer

Answer: b [Reason:] In regions of the estuary that are nutritionally poor, one is likely to find the budding and/or the appendaged bacteria, in addition to pseudomonads.

8. The characteristic color of the Red Sea is associated with heavy blooms of __________________
a) diatoms
b) cyanobacteria
c) dinoflagellates
d) chlamydomonads

View Answer

Answer: b [Reason:] The characteristic color of the Red Sea is associated with heavy blooms of a cyanobacterium, Oscillatoria erythraea, which contains the pigments phycoerythrin and phycocyanin.

9. Aquatic bacteria tend to be Gram-negative.
a) True
b) False

View Answer

Answer: a [Reason:] In general, aquatic bacteria tend to be Gram-negative. It is thought that the Gram-negative envelope provides a structure better suited to support life in nutritionally dilute aquatic environments than the Gram-positive cell wall.

10. Which of the following genus of bacteria is not found in fresh waters?
a) Pseudomonas
b) Flavobacterium
c) Aeromonas
d) Vibrio

View Answer

Answer: d [Reason:] Species of the following genera are commonly found in freshwater: Pseudomonas, Flavobacterium, Aeromonas and Alcaligenes. Vibrio are found in marine or estuarine waters.

Interview MCQ Set 2

1. The first demonstration of recombination in bacteria was achieved by _______________
a) Lederberg and Tatum
b) Luria and Delbruck
c) Joshua and Lederberg
d) Luria and Tatum

View Answer

Answer: a [Reason:] The first demonstration of recombination in bacteria was achieved by Lederberg and Tatum in 1946 in a brilliant and remarkable experiment that opened the door to a whole new world of microbiology.

2. Mating between species is necessary for recombination to take place.
a) True
b) False

View Answer

Answer: a [Reason:] In a regular cycle of sexual reproduction, there is an opportunity for different mutants of a species to mate with each other and produce new individuals with new combinations of mutations, i.e., to produce recombinants.

3. Which type of E.coli strain was chosen to prove the experiment of conjugation?
a) prototrophs
b) auxotrophs
c) polyauxotrophs
d) autotrophs

View Answer

Answer: c [Reason:] When Lederberg and Tatum did their experiments, they used polyauxotrophs (mutants with more than one nutritional requirement) so that back mutation to the wild type does not occur.

4. In conjugation only small fragments of the bacterial chromosome are transferred.
a) True
b) False

View Answer

Answer: b [Reason:] In conjugation it is possible for large segments of the chromosome, and in special cases the entire chromosome to be transferred.

5. What is the shape of DNA in the male cells of E.coli?
a) linear
b) supercoiled
c) circular
d) relaxed

View Answer

Answer: c [Reason:] Male cells contain a small circular piece of DNA, which is in the cytoplasm and not part of chromosome.

6. Which of the following cells of E.coli are referred to as F—?
a) Male cells
b) Female cells
c) Both male and female cells
d) Neither male nor female cells

View Answer

Answer: b [Reason:] Female cells lack the sex factor or F factor (fertility factor) and are labeled as F. They are recipient cells.

7. What is the frequency of formation of recombinants in a F+ X F cross?
a) 100
b) 40
c) 10
d) 1

View Answer

Answer: d [Reason:] The formation of recombinants in a F+ X F cross occurs at a low frequency— about one recombinant per 104 to 105 cells.

8. The F factor DNA is sufficient to specify how many genes?
a) 2
b) 10
c) 40
d) 100

View Answer

Answer: c [Reason:] The F factor DNA is only sufficient to specify about 40 genes which control sex-factor replication and synthesis of sex pili.

9. Which of the following is true for an Hfr X F— cross?
a) frequency of recombination high,transfer of F factor low
b) frequency of recombination high,transfer of F factor high
c) frequency of recombination low,transfer of F factor high
d) frequency of recombination low,transfer of F factor low

View Answer

Answer: a [Reason:] In an Hfr X F— cross, the frequency of recombination is high and the transfer of F factor is low as here the F factor of the Hfr is rarely transferred during recombination.

10. Which of the following can be used as a measure to construct a linkage map of the Hfr chromosome?
a) frequency of recombination
b) time of entry
c) locus of mutation
d) transfer of F factor

View Answer

Answer: b [Reason:] Each gene enters the F— cell at a characteristic time, and a linkage map of the Hfr chromosome can be constructed using time of entry as a measure.

11. The Hfr chromosome is transferred to the F— cell in a _____________ fashion.
a) circular
b) coiled
c) dimer
d) linear

View Answer

Answer: d [Reason:] The Hfr chromosome is transferred to the F— cell in a linear fashion even though it is a circular chromosome.

12. How much time is required to inject a copy of the whole Hfr E.coli genome?
a) 24 hrs
b) 30 mins
c) 100 mins
d) 48 hrs

View Answer

Answer: c [Reason:] It takes about 100 min to inject a copy of the whole Hfr E.coli genome (i.e., the chromosome and the integrated F factor.

Interview MCQ Set 3

1. The transfer of genes from one cell to another by a bacteriophage is known as __________________
a) Recombination
b) Conjugation
c) Transduction
d) Transformation

View Answer

Answer: c [Reason:] In bacteria, genetic recombination results from three types of gene transfer among which transfer of genes from one cell to another by a bacteriophage is known as transduction.

2. Genetic recombination occurs between homologous chromosomes.
a) True
b) False

View Answer

Answer: a [Reason:] Genetic recombination is the formation of a new genotype by reassortment of genes following an exchange of genetic material between two different chromosomes which have similar genes at corresponding sites. These are called homologous chromosomes and are from different individuals.

3. Bacterial recombination causes transformation of the recipient cell to _______________
a) donor cell
b) merozygote
c) zygote
d) recipient cell

View Answer

Answer: b [Reason:] The recipient cell becomes a merozygote, a zygote that is a partial diploid and then recombination can take place.

4. Transfer of genes between cells that are in physical contact with one another is known as transformation.
a) True
b) False

View Answer

Answer: b [Reason:] Transfer of genes between cells that are in physical contact with one another is known as conjugation.

5. Which of the enzymes are used to cut the recipient DNA?
a) endonuclease
b) exonuclease
c) ligases
d) polymerase

View Answer

Answer: a [Reason:] Endonuclease acts on the recipient DNA causing nicks and excision of a fragment of DNA to be replaced by donor DNA.

6. The transfer of naked DNA from one cell to another is referred to as _______________
a) Transduction
b) Lysogeny
c) Transformation
d) Conjugation

View Answer

Answer: c [Reason:] The transfer of cell-free or ‘naked’ DNA from one cell to another is called transformation.

7. The cell in which the F factor carries along with it some chromosomal genes are known as ____________
a) F+ cell
b) F— cell
c) F’ cell
d) F’’’ cell

View Answer

Answer: c [Reason:] Sometimes the F factor carries along with it some chromosomal genes and is termed as F’ factor, and the cell in which this has occurred is called an F’ cell.

8. What are bacteriocins?
a) proteins
b) toxins
c) plasmid
d) sex factor

View Answer

Answer: a [Reason:] Bacteriocins are proteins that kill the same or closely related species of bacteria and are formed by bacteriocinogenic factors.

Interview MCQ Set 4

1. How much time is taken by the new DNA to make whole phage particles?
a) 24 hours
b) 60 mins
c) 2 mins
d) 10-20 mins

View Answer

Answer: d [Reason:] Within 10 to 20 minutes, depending on the phage, the new DNA combines with the new proteins to make whole phage particles, which are released by destruction of the cell wall and lysis of the cell.

2. When viral genome can become integrated into the bacterial genome they are known as ____________
a) temperate phage
b) prophage
c) bacteriophage
d) episome

View Answer

Answer: b [Reason:] When viral genome can become integrated into the bacterial genome they are known as prophages. They carry DNA that can behave as a kind of episome in bacteria.

3. Bacteriophages inject their nucleic acid into the bacterium.
a) True
b) False

View Answer

Answer: a [Reason:] Bacteriophages inject their nucleic acid usually DNA into the bacterium where it replicates rapidly and also directs the synthesis of new phage proteins.

4. Which of the following role is performed by a bacteriophage in transduction?
a) vector
b) donor
c) recipient
d) episome

View Answer

Answer: a [Reason:] Bacterial transduction is the transfer by a bacteriophage, serving as a vector, of a portion of DNA from one bacterium (donor) to another (a recipient).

5. The viral DNA may be incorporated into the phage head during phage assembly.
a) True
b) False

View Answer

Answer: b [Reason:] Any part of the bacterial chromosome may be incorporated into the phage head during phage assembly and is usually not associated with any viral DNA.

6. What is the frequency of defective phage particles in progeny phage produced?
a) 100
b) 10-1
c) 10-5
d) 1000

View Answer

Answer: c [Reason:] The frequency of such defective phage particles is about 10-5 to 10-7 of the progeny phage produced.

7. Fragments transferred by a bacteriophage contains how many genes?
a) 20
b) 50
c) 1
d) 100

View Answer

Answer: d [Reason:] Generalized transduction provides a means for mapping bacterial genes, since the fragments transferred by a bacteriophage are often large enough to contain 100s of genes.

8. What is the correct order when coliphage P1 is grown in a thr+ leu+ aziR host is used to infect a thr- leu- azi- recipient bacterial cell?
a) thr+ leu+ aziR
b) thr leu+ aziR
c) thr+ leu aziR
d) thr leu aziR

View Answer

Answer: a [Reason:] When coliphage P1 is grown in a thr+ leu+ aziR host is used to infect a thr leu azi recipient bacterial cell then if Leu+ recombinants are selected, about 50 percent of these are also AzR.

9. How many percent of thr+ transducing phages also carry leu+?
a) 10%
b) 5%
c) 3%
d) 15%

View Answer

Answer: c [Reason:] Only 3% of thr+ transducing phages also carry leu+ shows that these two genes are so far apart that they are rarely included at the same time in a DNA fragment that goes into the P1 head.

10. When the phage transduces only those bacterial genes adjacent to the prophage in the bacterial chromosome then it is known as?
a) generalized transduction
b) specialized transduction
c) restricted transduction
d) conjugation

View Answer

Answer: c [Reason:] When the phage transduces only those bacterial genes adjacent to the prophage in the bacterial chromosome then it is known as restricted transduction.

Interview MCQ Set 5

1. What are the characteristics of rough pneumococci strain?
a) noncapsulated and pathogenic
b) noncapsulated and nonpathogenic
c) capsulated and pathogenic
d) capsulated and nonpathogenic

View Answer

Answer: b [Reason:] Griffith injected mice with a few rough (noncapsulated and nonpathogenic) pneumococci and a large number of heat-killed smooth cells.

2. In Griffith’s experiment which of the following strains of pneumococci was isolated from dead mice?
a) live rough cells
b) dead rough cells
c) live smooth cells
d) dead smooth cells

View Answer

Answer: c [Reason:] When Griffith injected mice with a mixture of a few rough and a large number of heat-killed smooth cells of pneumococci, then the mice subsequently died of pneumonia, and live smooth cells were isolated from their blood.

3. Which of the following things was identified as the transforming principle?
a) DNA
b) RNA
c) Proteins
d) Carbohydrates

View Answer

Answer: a [Reason:] Griffith showed in his experiment that DNA was the transforming principle that transformed the living rough bacteria into pathogenic smooth ones.

4. We require cell-free DNA for transformation to take place.
a) True
b) False

View Answer

Answer: a [Reason:] Transformation is the process whereby cell-free or naked DNA containing a limited amount of genetic information is transferred from one bacterial cell to another.

5. What should be the minimum weight of DNA that is required for successful transformation?
a) 1000 daltons
b) 100,000 daltons
c) 300,000 daltons
d) 8 million daltons

View Answer

Answer: c [Reason:] Molecular weights of DNA in the range of 300,000 to 8 million daltons have been shown to result in successful transformation.

6. How many DNA molecules are transferred after each transformation?
a) 2
b) 1
c) 50
d) infinite

View Answer

Answer: b [Reason:] Each transformation results from the transfer of a single DNA molecule of double-stranded DNA.

7. Which of the following enzymes acts on the DNA after its entry into the cell?
a) ligases
b) endonucleases
c) deoxyribonucleases
d) exonucleases

View Answer

Answer: c [Reason:] After DNA entry into a cell, one strand is immediately degraded by deoxyribonucleases, while the other strand undergoes base pairing with a homologous portion of the recipient cell chromosome.

8. Which among the following species have not been transformed?
a) Bacillus
b) Neisseria
c) Rhizobium
d) Aspergillus

View Answer

Answer: d [Reason:] Bacterial species that have been transformed include, besides Streptococcus pneumoniae, those in the genera Bacillus, Haemophilus, Neisseria, and Rhizobium.

9. In which phase of growth does the recipient cell takes up the donor DNA?
a) lag phase
b) early logarithmic phage
c) late logarithmic phage
d) stationary phage

View Answer

Answer: c [Reason:] Conditions suitable for uptake of donor DNA into recipient cells occur only during the late logarithmic phase of growth.

10. The DNA uptake process does not require any energy.
a) True
b) False

View Answer

Answer: b [Reason:] The uptake process has been found to be an energy-requiring mechanism because it can be inhibited by agents that interfere with energy metabolism.