Foreign DNA is ligated at the BamHI site of pBR322, and E. coli is transformed with the mix. Colonies are then tested on ampicillin and on tetracycline plates. Which ones carry the recombinant plasmid?

Those growing on ampicillin but not on tetracycline

Those growing on both ampicillin and tetracycline

Those growing on neither ampicillin nor tetracycline

Those growing on tetracycline but not on ampicillin

Biotechnology: Principles and Processes

27 NEET-UG practice questions on Biotechnology: Principles and Processes, part of Zoology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
Arrange these steps of DNA isolation from bacteria in the correct order. A. Add chilled ethanol to precipitate DNA B. Treat the cells with lysozyme C. Treat the lysate with protease and ribonuclease D. Spool out the fine threads of DNA
1. AB, C, A, D
2. BC, B, A, D
3. CB, A, C, D
4. DB, C, D, A
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Answer: A · B, C, A, D
The wall is broken first to release the contents. Protein and RNA are then removed with enzymes. Chilled ethanol precipitates the purified DNA, which is removed as fine threads by spooling.
- B: Enzymes cannot reach the contents until the wall is opened.
- C: Purification comes before ethanol precipitation.
- D: Threads can be spooled only after ethanol precipitation.
Remember this
DNA precipitates in chilled ethanol as fine threads; protease and ribonuclease remove the proteins and RNA bound or mixed with it.
Question 2 · Hard
Foreign DNA is ligated at the BamHI site of pBR322, and E. coli is transformed with the mix. Colonies are then tested on ampicillin and on tetracycline plates. Which ones carry the recombinant plasmid?
1. AThose growing on both ampicillin and tetracycline
2. BThose growing on ampicillin but not on tetracycline
3. CThose growing on neither ampicillin nor tetracycline
4. DThose growing on tetracycline but not on ampicillin
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Answer: B · Those growing on ampicillin but not on tetracycline
The insert inactivates tetR but leaves ampR intact, so recombinants grow on ampicillin but die on tetracycline. Colonies growing on both have the plasmid with no insert. Cells with no plasmid grow on neither.
- A: This describes a transformant with the plasmid but no insert.
- C: This describes a cell that took up no plasmid.
- D: This describes an insert at PvuI or PstI in ampR, not at BamHI.
Remember this
Recombinant at BamHI: amp-resistant, tet-sensitive. Non-recombinant plasmid: resistant to both. Non-transformant: resistant to neither.
Question 3 · Medium
A linear DNA molecule and a circular plasmid each carry four recognition sites for one restriction enzyme. On complete digestion, how many fragments does each give?
1. ALinear 4, plasmid 5
2. BLinear 4, plasmid 4
3. CLinear 5, plasmid 4
4. DLinear 5, plasmid 5
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Answer: C · Linear 5, plasmid 4
Each cut in a linear molecule adds a fragment, so n cuts give n + 1 pieces: 5. A circle has no ends: the first cut only opens it, so n cuts give n pieces: 4.
- A: This reverses the rule for linear and circular molecules.
- B: This forgets that linear DNA gains one extra piece.
- D: This forgets that a circle's first cut only opens it.
Remember this
Linear DNA with n sites gives n + 1 fragments; circular DNA with n sites gives n fragments.
Question 4 · Medium
Read these statements on colour selection using β-galactosidase. A. Inserting foreign DNA in the coding sequence raises β-galactosidase activity. B. Colonies carrying an insert give no colour on a chromogenic substrate. C. Colonies without an insert give blue colour on a chromogenic substrate. D. Colour selection needs no chromogenic substrate. Choose the correct option.
1. AA and B only
2. BC and D only
3. CB and C only
4. DB, C and D only
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Answer: C · B and C only
An insert within the β-galactosidase coding sequence inactivates the enzyme, so A is false. Without the enzyme there is no colour (B), while plasmids without an insert give blue colonies (C). D is false as the colour comes from a chromogenic substrate.
- A: This includes A, which reverses the effect of insertion.
- B: This includes D, which ignores the need for the substrate.
- D: This adds D, which is false because the substrate is essential.
Remember this
Blue colony means no insert; colourless colony means recombinant; this avoids plating simultaneously on two antibiotics.
Question 5 · Easy
In the enzyme name EcoRI, the letter R stands for the
1. ASpecies of the bacterium
2. BGenus of the bacterium
3. COrder of isolation
4. DStrain of the bacterium
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Answer: D · Strain of the bacterium
The first letter of the name comes from the genus and the next two from the species. R comes from the strain, RY13 of E. coli, and the Roman numeral gives the order of isolation.
- A: The species gives the next two letters, co.
- B: The genus gives the first letter, E.
- C: Order of isolation is shown by the Roman numeral.
Remember this
Eco = Escherichia coli, R = strain RY13, I = first enzyme isolated from that strain.
Question 6 · Easy
Agarose, used as the matrix for separating DNA fragments, is a natural polymer obtained from
1. AFungal hyphae
2. BSea weeds
3. CBacterial cell walls
4. DAnimal cartilage
Answer and explanation in LearnFree account
Question 7 · Hard
A 6 kb circular plasmid has one EcoRI site and one BamHI site, with 2 kb between them along the shorter arc. It is digested completely with both enzymes and run on agarose. What is seen?
1. A2 kb and 4 kb bands, with the 2 kb band farther from the well
2. B3 kb and 3 kb fragments, running together as one band
3. COne 6 kb band only, since the plasmid stays in one piece
4. D2 kb and 4 kb bands, with the 4 kb band farther from the well
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Question 8 · Easy
During a PCR, the enzyme that survives repeated heating to denature DNA comes from which bacterium?
1. ABacillus thuringiensis
2. BThermus aquaticus
3. CEscherichia coli
4. DAgrobacterium tumefaciens
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Question 9 · Medium
Assertion A: Ligating foreign DNA at the BamHI site of pBR322 makes the recombinant lose ampicillin resistance. Reason R: Inserting foreign DNA within a gene can inactivate that gene. Choose the correct answer.
1. ABoth A and R are correct but R is not the correct explanation of A
2. BBoth A and R are correct and R is the correct explanation of A
3. CA is not correct but R is correct
4. DA is correct but R is not correct
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Question 10 · Medium
In a continuous culture system, used medium is drained from one side while fresh medium is added from the other. What is the purpose?
1. AKeeping cells in stationary phase so that they stop dividing
2. BAvoiding the need for any oxygen supply to the culture
3. CKeeping cells in their most active log phase for higher yield
4. DRemoving the recombinant plasmid from the growing culture
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Question 11 · Hard
Applying the palindrome rule for restriction sites, in which sequence does the top strand read the same as its partner strand, each read in the 5′→3′ direction?
1. A5′-GGTTGG-3′
2. B5′-GATTAG-3′
3. C5′-GGTACC-3′
4. D5′-ACGACG-3′
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Question 12 · Medium
Match List-I with List-II. List-I (method) A. Micro-injection B. Biolistics C. Disarmed pathogen vector D. Heat shock List-II (description) I. High-velocity gold or tungsten particles coated with DNA, suited to plants II. DNA placed directly into the nucleus of an animal cell III. Bacterial cells held briefly at 42°C after calcium treatment IV. Allowed to infect a cell and so transfers recombinant DNA to it
1. AA-I, B-II, C-IV, D-III
2. BA-IV, B-I, C-II, D-III
3. CA-II, B-I, C-IV, D-III
4. DA-II, B-I, C-III, D-IV
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Question 13 · Hard
A vector was cut with EcoRI and an insert with BamHI, then both were mixed with DNA ligase, yet no recombinant formed. What is the most direct reason?
1. AEcoRI always destroys the origin of replication of the vector
2. BDNA ligase can join only the blunt ends that exonucleases leave behind
3. CThese two enzymes cut only one strand of the DNA double helix
4. DThe overhanging single-stranded ends of vector and insert are not complementary
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Question 14 · Medium
Three molecules of template DNA are amplified in a PCR, and every cycle exactly doubles the DNA. How many molecules are present after 6 cycles?
1. A64
2. B192
3. C18
4. D96
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Question 15 · Medium
Given below are two statements: Statement I: Exonucleases make cuts at specific positions within the DNA. Statement II: A restriction endonuclease cuts each strand of the double helix at specific points in its sugar-phosphate backbone. Choose the correct answer.
1. ABoth Statement I and Statement II are correct
2. BStatement I is incorrect but Statement II is correct
3. CBoth Statement I and Statement II are incorrect
4. DStatement I is correct but Statement II is incorrect
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Question 16 · Easy
After agarose gel electrophoresis, DNA appears as bright orange bands on exposure to UV radiation. Which stain was used?
1. AAcetocarmine
2. BSafranin
3. CMethylene blue
4. DEthidium bromide
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Question 17 · Medium
Arrange these steps of a recombinant DNA experiment in the correct order. A. Select host cells that took up the recombinant plasmid B. Cut the gene source and vector with one restriction enzyme C. Join the insert to the vector with DNA ligase D. Introduce the recombinant DNA into competent host cells
1. AC, B, D, A
2. BB, C, A, D
3. CB, D, C, A
4. DB, C, D, A
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Question 18 · Easy
Which of these is NOT a selectable marker useful for E. coli transformation?
1. AThe rop gene
2. BAmpicillin-resistance gene
3. CKanamycin-resistance gene
4. DTetracycline-resistance gene
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Question 19 · Medium
Match List-I with List-II. List-I (enzyme) A. Restriction endonuclease B. DNA ligase C. Lysozyme D. Ribonuclease List-II (role in a DNA experiment) I. Joins DNA fragments II. Breaks the bacterial cell wall III. Cuts DNA at a specific sequence IV. Removes RNA from the preparation
1. AA-I, B-III, C-II, D-IV
2. BA-III, B-I, C-IV, D-II
3. CA-III, B-II, C-I, D-IV
4. DA-III, B-I, C-II, D-IV
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Question 20 · Medium
Given below are two statements: Statement I: Treating bacterial cells with a divalent cation such as calcium improves the efficiency with which DNA enters through pores in the wall. Statement II: Recombinant DNA can be forced into such cells by incubating them on ice, placing them briefly at 42°C and returning them to ice. Choose the correct answer.
1. ABoth Statement I and Statement II are incorrect
2. BBoth Statement I and Statement II are correct
3. CStatement I is incorrect but Statement II is correct
4. DStatement I is correct but Statement II is incorrect
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Question 21 · Medium
Read these statements on the cloning vector pBR322. A. ori is the site normally used for ligating foreign DNA. B. rop codes for proteins involved in replication of the plasmid. C. PvuI and PstI sites lie within the ampicillin-resistance gene. D. BamHI and SalI sites lie within the tetracycline-resistance gene. Choose the correct option.
1. AB, C and D only
2. BB and C only
3. CA, C and D only
4. DA, B and C only
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Question 22 · Easy
A DNA isolation protocol begins with fungal cells. Which enzyme is added to break the cell wall?
1. ARibonuclease
2. BChitinase
3. CLysozyme
4. DCellulase
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Question 23 · Medium
Match List-I with List-II. List-I (part of a stirred-tank bioreactor) A. Stirrer B. Sparger C. Foam breaker D. Sampling port List-II (function) I. Lets small culture volumes be withdrawn periodically II. Delivers sterile air bubbles into the culture III. Gives even mixing and oxygen availability IV. Keeps froth from building up above the broth
1. AA-II, B-III, C-IV, D-I
2. BA-III, B-II, C-IV, D-I
3. CA-IV, B-II, C-III, D-I
4. DA-III, B-II, C-I, D-IV
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Question 24 · Easy
The temperature record of a PCR run is plotted. During which marked segment does Taq polymerase extend the primers?
Figure: MedExams
1. ASegment Q
2. BSegment P
3. CSegment R
4. DSegment S
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Question 25 · Hard
A linear DNA of 12 kb has one EcoRI site and one BamHI site. It is digested with each enzyme alone and with both, and the fragments are run on the gel shown. How far apart are the two sites?
Figure: MedExams
1. A3 kb
2. B2 kb
3. C4 kb
4. D7 kb
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Study Zoology

Biotechnology: Principles and Processes

Arrange these steps of DNA isolation from bacteria in the correct order. A. Add chilled ethanol to precipitate DNA B. Treat the cells with lysozyme C. Treat the lysate with protease and ribonuclease D. Spool out the fine threads of DNA

Foreign DNA is ligated at the BamHI site of pBR322, and E. coli is transformed with the mix. Colonies are then tested on ampicillin and on tetracycline plates. Which ones carry the recombinant plasmid?

A linear DNA molecule and a circular plasmid each carry four recognition sites for one restriction enzyme. On complete digestion, how many fragments does each give?

In the enzyme name EcoRI, the letter R stands for the

Agarose, used as the matrix for separating DNA fragments, is a natural polymer obtained from

A 6 kb circular plasmid has one EcoRI site and one BamHI site, with 2 kb between them along the shorter arc. It is digested completely with both enzymes and run on agarose. What is seen?

During a PCR, the enzyme that survives repeated heating to denature DNA comes from which bacterium?

Assertion A: Ligating foreign DNA at the BamHI site of pBR322 makes the recombinant lose ampicillin resistance. Reason R: Inserting foreign DNA within a gene can inactivate that gene. Choose the correct answer.

In a continuous culture system, used medium is drained from one side while fresh medium is added from the other. What is the purpose?

Applying the palindrome rule for restriction sites, in which sequence does the top strand read the same as its partner strand, each read in the 5′→3′ direction?

A vector was cut with EcoRI and an insert with BamHI, then both were mixed with DNA ligase, yet no recombinant formed. What is the most direct reason?

Three molecules of template DNA are amplified in a PCR, and every cycle exactly doubles the DNA. How many molecules are present after 6 cycles?

Given below are two statements: Statement I: Exonucleases make cuts at specific positions within the DNA. Statement II: A restriction endonuclease cuts each strand of the double helix at specific points in its sugar-phosphate backbone. Choose the correct answer.

After agarose gel electrophoresis, DNA appears as bright orange bands on exposure to UV radiation. Which stain was used?

Which of these is NOT a selectable marker useful for E. coli transformation?

Match List-I with List-II. List-I (enzyme) A. Restriction endonuclease B. DNA ligase C. Lysozyme D. Ribonuclease List-II (role in a DNA experiment) I. Joins DNA fragments II. Breaks the bacterial cell wall III. Cuts DNA at a specific sequence IV. Removes RNA from the preparation

A DNA isolation protocol begins with fungal cells. Which enzyme is added to break the cell wall?

The temperature record of a PCR run is plotted. During which marked segment does Taq polymerase extend the primers?

A linear DNA of 12 kb has one EcoRI site and one BamHI site. It is digested with each enzyme alone and with both, and the fragments are run on the gel shown. How far apart are the two sites?