Plasmids MCQ

A plasmid is a tiny extrachromosomal DNA molecule that can replicate independently of chromosomal DNA and is physically isolated from it. Plasmids are small circular double-stranded DNA molecules that are most typically found in bacteria; however, they can also be found in archaea and eukaryotic cells.

1. Maximum size of foreign DNA that can be inserted into a replacement vector is

1. 1. 25-30 kb
   2. 18-20 kb
   3. 20-25 kb
   4. 40-50 kb

Correct Option: C

Explanation:

The maximum size of foreign DNA that can be inserted into a replacement vector is between 20-25kb.

2. Which of the following is not true about phagemid?

1. 1. Contain functional origin of replication of the plasmid and λ phage
   2. May be propagated as a plasmid or as phage in appropriate strain
   3. Contain λ att site
   4. Can only be propagated as phage

Correct Option: A

Explanation:

The plasmid is a single circular extrachromosomal DNA which carries antibiotic-resistant genes and origin of replication i.e., the ability of autonomous replication and its size is smaller than chromosomal DNA. These characters of plasmid make it an ideal vector for recombinant DNA technology.

3. pBR 322 has/have which of the following selection marker(s)?

1. 1. Ampr
   2. Tetr
   3. Both (a) and (b
   4. Kanr

Correct Option: C

Explanation:

pBR322 contains two selectable markers, i.e. antibiotic resistance genes for ampicillin (ampR) and tetracycline (tetR).

4. A plasmid can be considered as a suitable cloning vector if

1. 1. it can be readily isolated from the cells
   2. it possesses a single restriction site for one or more restriction enzymes
   3. insertion of foreign DNA does not alter its replication properties
   4. All of the above

Correct Option: A

Explanation:

Plasmids are autonomously replicating circular extrachromosomal DNA. They are the standard cloning vectors and the ones most used. Most general plasmids may be used to clone DNA inserts of up to 15 kb in size.

5. Difference between λ gt 10 and λ gt 11 vectors is that

1. 1. λ gt 11 is an expression vector
   2. λ gt 10 is an expression vector
   3. λ gt 10 is a replacement vector
   4. λ gt 11 is a replacement vector

Correct Option: A

Explanation:

Difference between λ gt 10 and λ gt 11 vectors is that λ gt 11 is an expression vector.

6. λ ZAP vector is an example of

1. 1. phage
   2. phagemid
   3. cosmid
   4. plasmid

Correct Option: B

Explanation:

Lambda ZAP: a bacteriophage lambda expression vector with in vivo excision properties.

7. λ gt 10 and λ gt 11 vectors can propagate cloned fragments up to

1. 1. 6-7 kb
   2. 1-2 kb
   3. 40-44 kb
   4. 20-23 kb

Correct Option: A

Explanation:

λ gt 10 and λ gt 11 vectors can propagate cloned fragments up to 6-7kb.

8. Select the wrong statement about plasmids?

1. 1. It is extrachromosomal
   2. It is double stranded
   3. Its replication depends upon host cell
   4. It is closed and circular DNA

Correct Option: C

Explanation:

Plasmids replication does not depend upon the host cell.

9. Stuffer is

1. 1. the right arm of the vector DNA
   2. the left arm of the vector DNA
   3. central fragment of the vector DNA
   4. none of the above

Correct Option: C

Explanation:

Stuffer is called the central fragment of vector DNA.

10. Conjugative plasmids

1. 1. exhibit antibiotic resistance
   2. do not exhibit antibiotic resistance
   3. carry transfer genes called the tra genes
   4. do not carry transfer genes

Correct Option: A

Explanation:

Conjugative plasmids exhibit antibiotic resistance.

11. Plasmid incompatibility is

1. 1. inability of a plasmid to grow in the host
   2. inability of two different plasmids to coexist in the same host cell in the absence of selection pressure.
   3. both (a) and (b)
   4. none of the above

Correct Option: B

Explanation:

It is the inability of two different plasmids to coexist in the same host cell in the absence of selection pressure.

12. P1 cloning vector allow cloning of DNA of the length of

1. 1. 100 kbp
   2. 50 kbp
   3. 20 kbp
   4. 10 kbp

Correct Option: A

13. Charon 34 and Charon 35 can clone DNA upto

1. 1. 1-2 kb
   2. 6-7 kb
   3. 9-20 kb
   4. 30-35 kb

Correct Option: C

Charon 34 and Charon 35 can clone DNA upto 9-20kb.

14. Charon vectors are different from EMBL vectors because

1. 1. They have a more extensive range of restriction targets within their polylinkers.
   2. physical separation of lambda arm from central fragment is required
   3. both (a) and (b)
   4. physical separation of lambda arm from central fragment is not required

Correct Option: C

Explanation:

Charon vectors are different from EMBL vectors because they have a more extensive range of restriction targets within their polylinkers; physical separation of the lambda arm from the central fragment is required.

15. Cos site of the cosmids

1. 1. consists of 12 bases
   2. helps whole genome in circularization and ligation
   3. both (a) and (b)
   4. contains cleavage site

Correct Option: C

Explanation:

Cosmids are plasmids with cos, or cohesive ends, sites, which are sequences essential for the packaging of DNA into phage particles. A plasmid origin of DNA replication, at least one selectable marker, and helpful restriction endonuclease sites are all included in cosmids.

16. M 13 is an example of

1. 1. filamentous phage
   2. single stranded DNA vector
   3. both (a) and (b)
   4. plasmid

Correct Option: B

Explanation:

M 13 is an example of filamentous phage single stranded DNA vector bot.

17. Phagemid vectors are

1. 1. combination of plasmid and phage λ
   2. combination of phages and cosmid
   3. phages carrying properties of plasmids
   4. all of the above

Correct Option: A

Explanation:

A plasmid is a tiny extrachromosomal DNA molecule that can replicate independently of chromosomal DNA and is physically isolated from it. Plasmids are small circular double-stranded DNA molecules that are most typically found in bacteria; however, they can also be found in archaea and eukaryotic cells.

18. Single stranded vectors are useful

1. 1. for sequencing of cloned DNA
   2. for oligonucleotide directed mutagenesis
   3. for probe preparation
   4. all of the above

Correct Option: D

Explanation:

Single stranded vectors are useful for sequencing

19. Inserted DNA in λ gt 11 can be expressed as

1. 1. β-galactosidase fused protein
   2. free protein in the cytoplasm
   3. free protein that is secreted out
   4. all of the above

Correct Option: A

Explanation:

Inserted DNA in λ gt 11 can be expressed as β-galactosidase fused protein.