Pharmaceutical Biotechnology Quiz on “Genetic Recombination – Conjugation”.
1. By whose experiment evidence of the existence of conjugation was established?
a) Robert Hook
b) Albert Einstein
c) Thomas Bill and Jimmy Bill
d) Joshua Lederberg and Edward Tatum
Answer: d
Clarification: The evidence for conjugation was discovered by the experiment of Joshua Lederberg and Edward Tatum in the year 1946. They found out genetic material can be transferred by direct cell to cell contact.
2. By whose experiment conjugation was proved?
a) Robert Hook
b) Bernard Davis
c) Thomas Bill and Jimmy Bill
d) Joshua Lederberg and Edward Tatum
Answer: b
Clarification: Lederberg and Tatum did not prove the facts of conjugation. The evidence for conjugation was provided by Berners Davis. He proved the fact that physical contact of cells was necessary for gene transfer. It was in the year 1950.
3. Which one of the following is true?
a) The F plasmid encodes the factor which is transferred from one cell to another
b) The factor encoded by the F plasmid is called as Filamentous (F) factor
c) It is transferred from one cell to another by filament
d) The bacteria must belong to the same species to carry out the conjugation
Answer: a
Clarification: F plasmid encodes the factor called Fertility or F factor. It is transferred from one cell to another by the sex pilus. It is present in E. coli and for the conjugation to take place; bacteria can also belong to different species.
4. Which of the following made it easier to conclude that physical contact of the cells was necessary for conjugation in Davis experiment?
a) Filter
b) U – tube
c) Separate medium for different strains of bacterium
d) Distant species of bacterium
Answer: a
Clarification: After 4 hours of incubation in the medium within u tube Davis found that since the bacteria were not allowed for direct contact they could not exchange genetic material. It was the fritted glass filter that allowed the passage of the media but not the bacteria.
5. Who releases the plasmid encoded proteins required for adhering.
a) Donor cell
b) Recipient cell
c) F+ cell
d) F- cell
Answer: a
Clarification: Few transfer genes are required for gene transfer in this system. It doesn’t incorporate a sex pilus for plasmid transfer. Donor and recipient cells adhere to each other using specialised plasmid encoded protein released by the donor cell.
6. Sex pilus is not required for plasmid transfer.
a) True
b) False
Answer: a
Clarification: Self transmissible plasmids are present in gram positive bacteria. Few transfer genes are required for gene transfer in this system. It doesn’t incorporate a sex pilus for plasmid transfer.
7. Conjugation can’t take place between ___________
a) F- and F+
b) F’ and F-
c) HFR and F-
d) HFR and F+
Answer: d
Clarification: For conjugation to take place one bacterium must have the F plasmid and others should lack it. HFR has the components of F plasmid within its genome so it can’t mate with another F+.
8. Which one of the following do not have a self-transmissible plasmid?
a) E. colli
b) Streptococcus
c) Bacillus
d) Enterococcus
Answer: a
Clarification: Self transmissible plasmid are only present on gram positive bacteria such as Bacillus, Streptococcus, Enterococcus, Staphylococcus, and Streptomyces. For these organisms the sex pilus is not required for plasmid transfer.
9. Which one of the following gets transferred during Hfr conjugation?
a) F factor
b) F- factor
c) Donor DNA
d) Donor plasmid
Answer: c
Clarification: In Hfr conjugation the donor DNA gets replicated by rolling circle method and transferred from the Hfr to the F- cell through the connected pillus. The fragmented donor DNA gets incorporated into the recipient’s chromosome.
10. In conjugation of F+ cell and F– cell the recipient will be F–.
a) True
b) False
Answer: b
Clarification: In F+ and F– mating the F factor is replicated by rolling cycle replication and taken up by the recipient cell. Thus the recipient cell becomes F+ not F–. Due to the replication and transfer of F factor both the bacteria become F+.
11. What is the order of the gene where columns are for different HFR and values denote time?
a) Azi, Lac, Gal, Ton
b) Lac, Gal, Azi, Ton
c) Gal, Lac, Ton, Azi
d) Tob, Azi, Lac, Gal
Answer: b
Clarification: The HFR can be produced by incorporation of the plasmid within the DNA at different positions. So here in two cases, the position is different. Considering the relative time of entry, we can see a pattern which agrees with option 2. It can be in either orientation.
12. Conjugation between F+ and F– cell results in _______________
a) Two F– cells
b) F–cell becomes F+
c) F– cell remains F– cell with a little DNA from F+ cell
d) Remains the same without any change
Answer: b
Clarification: Conjugation occurs between positive and negative F cells. The donor cell will have pilus and this pilus will attach to the recipient cell thus bringing the two cell together. The F plasmid will be an episome.
13. What is the unidirectional transfer of genetic material from the donor to the recipient is termed?
a) Conjugation
b) Recombination
c) Transduction
d) Transformation
Answer: a
Clarification: Transfer of genetic material from a donor bacterium to recipient bacterium by a cell to cell contact is termed as conjugation. The donor bacterium has a DNA sequence with the Fertility factor.
14. What genetic information (DNA) does an F-plasmid contain?
a) Chromosomal DNA
b) Non-chromosomal DNA with regulatory genes
c) DNA that codes for proteins to produce pili
d) B and C
Answer: d
Clarification: F-plasmids contain genetic information that is not present in the bacterial chromosomes, although they can be integrated with the chromosomes.
15. In conjugation of HFr cell with F– cell the recipient ______________
a) Stays F–
b) Become F+
c) Become HFr
d) Become F’
Answer: a
Clarification: Since entire plasmid cannot transfer the recipient remains F–. Hfr cell can transfer a portion of the bacterial genome. The bacterium receiving the genes do not become F+.