This set of Genetic Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Lambda ZAP and Cosmids”.
1. Choose the correct statement for the lambda ZAP vector.
a) It is not based on bacteriophage lambda
b) It contains a region that can be excised in vivo
c) The excision leads to the formation of bluescript plasmids and it contains an initiator region only
d) The multiple cloning site is not flanked by the initiator and the terminator region
View Answer
Explanation: Lambda ZAP vector is based on the bacteriophage lambda. It contains a region that can be excised in vivo and leads to the formation of bluescript plasmids. This consists of multiple cloning site which is flanked by the initiator and the terminator region.
2. The initiator is recognized by which gene?
a) Gene I
b) Gene I and II
c) Only gene II
d) Gene III
View Answer
Explanation: The f1 initiator and terminator region flanks the multiple cloning site and the initiator region is recognized by gene II.
3. Choose the incorrect statement for the replication process.
a) The initiator site is nicked and replication of one strand is started
b) Replication takes place in both the directions
c) Replication continues through the bluescript
d) It is stopped at the terminator and then again a nick is made
View Answer
Explanation: The initiator site is nicked and the replication of one strand is initiated. Replication takes place in one direction only and continues through the bluescript. It is stopped at the terminator and then a nick is made again there.
4. Which of the following doesn’t takes place after replication?
a) The single stranded sequence is generated
b) It is circularized to form closed single stranded molecule
c) It may circularize or remain linear
d) The double stranded molecule can be synthesized by cellular DNA synthesis
View Answer
Explanation: As the replication takes place, a single stranded sequence is generated and it circularizes in vivo in order to form single stranded circular molecule. The double stranded molecule can be synthesized by cellular DNA synthesis.
5. Choose the correct statement for cosmids.
a) It can be regarded as lambda substitution vector
b) Less amount of phage DNA is deleted
c) Only cos packaging sites are left
d) It doesn’t contains a origin of replication
View Answer
Explanation: Cosmids can be regarded as lambda replacement vectors. More amount of phage DNA is deleted and only cos packaging sites are left. There are no coat protein genes left. It also contains an origin of replication.
6. Once cosmids are inside the E.coli cells, they don’t generate phage but are propagated as plasmids.
a) True
b) False
View Answer
Explanation: Once cosmids are inside the E. coli cells, they don’t generate more phage but are propagated as plasmids. It is so because no more coat protein genes are present and thus it can’t be packaged. They can’t give rise to plaques.
7. Which of the following is the correct method to check whether the DNA has entered into the cell or not in the case of cosmid?
a) If a transformation has taken place turbid plaques are formed
b) If a transformation has taken place clear plaques are formed
c) If a transformation has taken place, it can be confirmed via ampicillin resistance
d) If a transformation has taken place, it can be confirmed if forms plaques and is ampicillin resistant also
View Answer
Explanation: In the case of cosmid, transformation can be confirmed via counting the colonies containing ampicillin. As the plaques are not formed by cosmids, it can’t be used as a method to detect transformation.
8. Which size of the insert is accepted by the cosmids?
a) 10-20 kbp
b) 35-45 kbp
c) 50-60 kbp
d) 100-120 kbp
View Answer
Explanation: There is a minimum size limit on the insert which is accepted by the cosmids and it lies in the range of 35-45 kbp. They generally accept large size insert and it is beneficial for the construction of genomic libraries.
9. What happens once the cosmid enters the E. coli cells?
a) There is strict size selection inside E. coli cells
b) Partial deletion may take place
c) The tendency of deletion may is increased by using low copy number
d) The tendency of deletion can’t be altered
View Answer
Explanation: There is no size selection once the cosmid enters the E. coli cells. Because of it, partial deletion may take place. The tendency of deletion can be reduced by using a low copy number.
10. If colEI derived origin of replication is replaced by the origin of replication of F plasmid, it is called as:
a) phagemid
b) F cosmid
c) plasmid
d) fosmid
View Answer
Explanation: If colE1 derived origin of replication is replaced by the origin of replication of F plasmid it is known as fosmid. F plasmids are present in a low copy number.
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