Which of the following statements are not true regarding restriction endonucleases? A. They are called molecular scissors. B. These are the enzymes responsible for restricting the growth of bacteriophages in E. coli. C. They cut the DNA only at the centre of the palindromic sites. D. They remove nucleotides only from the ends of DNA fragments. E. They recognise specific palindromic base-pair sequences. Choose the answer from the options given below:

Let's review the statements about restriction endonucleases: - A is true: They are commonly known as molecular scissors. - B is true: They form part of the defense mechanism in bacteria (like E. coli) to restrict bacteriophage growth by cutting viral DNA. - C is false: They typically cut the DNA slightly away from the centre of the palindrome sites, but between the same two bases on the opposite strands, which creates sticky ends. - D is false: Removing nucleotides from the ends of DNA is the function of restriction **exonucleases**, not endonucleases. Endonucleases cut at specific positions *within* the DNA. - E is true: They do recognize specific palindromic nucleotide sequences. The statements that are NOT true are C and D. Endo = inside. Exo = outside (ends). Therefore, D is clearly false for an endonuclease. They create sticky ends by cutting off-center, making C false. Class 12 Biology: Biotechnology Principles and Processes

Which of the following statements are not true regarding restriction endonucleases? A. They are called molecular scissors. B. These are the enzymes responsible for restricting the growth of bacterioph

Let's review the statements about restriction endonucleases: - A is true: They are commonly known as molecular scissors. - B is true: They form part of the defense mechanism in bacteria (like E. coli) to restrict bacteriophage growth by cutting viral DNA. - C is false: They typically cut the DNA slightly away from the centre of the palindrome sites, but between the same two bases on the opposite strands, which creates sticky ends. - D is false: Removing nucleotides from the ends of DNA is the fu

Which of the following statements are not true regarding restriction endonucleases? A. They are called molecular scissors. B. These are the enzymes responsible for restricting the growth of bacteriophages in E. coli. C. They cut the DNA only at the centre of the palindromic sites. D. They remove nucleotides only from the ends of DNA fragments. E. They recognise specific palindromic base-pair sequences. Choose the answer from the options given below:

Let's review the statements about restriction endonucleases: - A is true: They are commonly known as molecular scissors. - B is true: They form part of the defense mechanism in bacteria (like E. coli) to restrict bacteriophage growth by cutting viral DNA. - C is false: They typically cut the DNA slightly away from the centre of the palindrome sites, but between the same two bases on the opposite strands, which creates sticky ends. - D is false: Removing nucleotides from the ends of DNA is the function of restriction **exonucleases**, not endonucleases. Endonucleases cut at specific positions *within* the DNA. - E is true: They do recognize specific palindromic nucleotide sequences. The statements that are NOT true are C and D. Endo = inside. Exo = outside (ends). Therefore, D is clearly false for an endonuclease. They create sticky ends by cutting off-center, making C false. Class 12 Biology: Biotechnology Principles and Processes

Which of the following statements are not true regarding restriction endonucleases? A. They are called molecular scissors. B. These are the enzymes responsible for restricting the growth of bacterioph

Let's review the statements about restriction endonucleases: - A is true: They are commonly known as molecular scissors. - B is true: They form part of the defense mechanism in bacteria (like E. coli) to restrict bacteriophage growth by cutting viral DNA. - C is false: They typically cut the DNA slightly away from the centre of the palindrome sites, but between the same two bases on the opposite strands, which creates sticky ends. - D is false: Removing nucleotides from the ends of DNA is the fu

Which of the following statements are not true regarding restriction endonucleases? A. They are called molecular…

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Q110 neet_2026_03_may_morning Cloning Vectors and Enzymes

Match List I with List II:

List-I	List-II
A. Genetically modified organism	(I) Agrobacterium tumefaciens
B. Thermostable DNA polymerase	(II) Bt cotton
C. Ti plasmid	(III) Thermus aquaticus
D. pBR322	(IV) Escherichia coli

Choose the correct answer from the options given below:

A. $A-II, B-I, C-IV, D-III$ $\text{A-II, B-I, C-IV, D-III}$
B. $A-I, B-IV, C-III, D-II$ $\text{A-I, B-IV, C-III, D-II}$
C. $A-II, B-III, C-I, D-IV$ $\text{A-II, B-III, C-I, D-IV}$
D. $A-I, B-II, C-IV, D-III$ $\text{A-I, B-II, C-IV, D-III}$

Solution

Core Logic

Genetically modified organism (A): Bt cotton is a famous transgenic (GMO) crop. (A-II)
Thermostable DNA polymerase (B): Taq polymerase, used in PCR, is isolated from the hot spring bacterium Thermus aquaticus. (B-III)
Ti plasmid (C): Tumor-inducing plasmid is extracted from the plant pathogen Agrobacterium tumefaciens. (C-I)
pBR322 (D): The classic, artificially engineered plasmid vector used in Escherichia coli. (D-IV)

Step 1: Final Conclusion

The exact mapping is A-II, B-III, C-I, D-IV.

Pattern Recognition

Matching Taq (Thermostable) with Thermus aquaticus (B-III) and Ti Plasmid with Agrobacterium (C-I) are the most direct routes to the answer.

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Class 12 Biology: Biotechnology Principles and Processes Class 12 Biology: Biotechnology and its Applications

Q119 neet_2026_03_may_morning Polymerase Chain Reaction

Identify the correct sequence of steps in each cycle of Polymerase Chain Reaction :

A. Denaturation → Annealing → Extension
B. Denaturation → Extension → Annealing
C. Extension → Annealing → Denaturation
D. Annealing → Denaturation → Extension

Solution

Core Logic

A single cycle of Polymerase Chain Reaction (PCR) consists of three main steps:

Denaturation: Heating the double-stranded DNA to separate the strands (around $94°C$ $94^{\circ}C$).
Annealing: Cooling the reaction so that primers can bind (anneal) to their complementary sequences on the single-stranded template DNA.
Extension: Taq polymerase synthesizes the new DNA strand by extending the primers.

Step 1: Final Conclusion

The correct sequence is Denaturation → Annealing → Extension.

Pattern Recognition

Acronym: DAE (Denaturation, Annealing, Extension).

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Class 12 Biology: Biotechnology Principles and Processes

Q120 neet_2026_03_may_morning Gel Electrophoresis

Which of the following statements are correct with respect to DNA separation, isolation and visualization? A. The cutting of DNA is done by molecular scissors. B. The DNA fragments separate according to their size in an agarose gel, upon electrophoresis. C. The separated DNA fragments can be seen without staining when exposed to UV light. D. The separated DNA fragments, when stained with ethidium bromide, can be seen in visible light. Choose the correct answer from the options given below :

A. A and D only
B. B and D only
C. B and C only
D. A and B only

Solution

Core Logic

Statement A is correct. DNA cutting is performed by restriction endonucleases, often referred to as molecular scissors.
Statement B is correct. During gel electrophoresis, DNA fragments (which are negatively charged) move towards the anode and separate strictly according to their size due to the sieving effect of the agarose gel.
Statement C is incorrect. Pure DNA fragments are invisible and cannot be seen under UV light without prior staining.
Statement D is incorrect. Even when stained with ethidium bromide, DNA fragments are invisible in visible (normal) light; they only fluoresce bright orange when exposed to UV radiation.

Step 1: Final Conclusion

Only statements A and B are correct.

Pattern Recognition

Visualizing DNA requires BOTH staining (Ethidium bromide) AND UV light. Statements C and D break this rule by missing one of the prerequisites.

Chapter Mix

Class 12 Biology: Biotechnology Principles and Processes

Q136 neet_2026_03_may_morning Cloning Vectors

Insertion of a foreign DNA at BamHI site in an E.coli cloning vector pBR322 results in the loss of antibiotic resistance towards:

A. Gentamycin
B. Ampicillin and tetracycline
C. Tetracycline
D. Ampicillin

Solution

Core Logic

The cloning vector pBR322 possesses two main antibiotic resistance genes: $ampR$ $amp^{R}$ (ampicillin resistance) and $tetR$ $tet^{R}$ (tetracycline resistance). The restriction site for BamHI is located directly within the $tetR$ $tet^{R}$ gene. If a foreign DNA is ligated at the BamHI site, insertional inactivation of the $tetR$ $tet^{R}$ gene occurs.

Step 1: Final Conclusion

Due to this insertional inactivation, the recombinant plasmid loses its resistance to tetracycline.

Pattern Recognition

BamHI and SalI are in the Tetracycline resistance gene. PvuI and PstI are in the Ampicillin resistance gene.

Chapter Mix

Class 12 Biology: Biotechnology Principles and Processes

Solution & Explanation

Core Logic

Step 1: Final Conclusion

Pattern Recognition

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