CBSE Questions for Class 12 Medical Biology Biotechnology: Principles And Processes Quiz 12 - MCQExams.com

• A restriction enzyme restriction endonuclease is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites.
• Methylase is an enzyme that adds a methyl group to the adenine of the sequence 5'-GATC-3' in newly synthesized DNA.
• Hence A is a restriction endonuclease and B is a methylase in structure labelled A and B respectively
• So the correct answer is 'A is a restriction endonuclease and B is a methylase'.

• Restriction enzymes cut foreign DNA, such as viral DNA, into fragments.
• Bacteria protect their own DNA by modifying bases, usually by methylation, at the recognition sites.
  
• Hence,  the bacteria protects its own genome from degradation by restriction endonucleases by Site-specific methylation of its own DNA.
• So, the correct answer is 'Site-specific methylation of its own DNA'.

• pBR322 is a plasmid and widely used E. coli cloning vector. 
• pBR322 contains the ampR gene, encoding the ampicillin resistance protein, the tetR gene, encoding the tetracycline resistance protein, and the rop gene, encoding a restrictor of plasmid copy number. 
• The plasmid has unique restriction sites for over forty restriction enzymes. 
• 11 of these 40 sites lie within the tetR gene. 
• There are 2 sites for restriction enzymes HindIII and ClaI within the promoter of the tetR gene. 
• There are 6 key restriction sites inside the ampR gene. 

• Several chemicals have been used to induce protoplast fusion.
• Sodium nitrate (NaN03), polyethene glycol (PEG), Calcium ions (Ca2+), Polyvinyl alcohol etc. are the most commonly used protoplast fusion inducing agents which are commonly known as chemical fusogens. 
• Hence, PEG is used for Fusing of protoplasts.
•  So, the correct answer is 'Fusing of protoplasts'.

$$\textbf{Correct answer: C}$$ 

$$\textbf{Option (C):}$$ 

$$\bullet$$ Some unarmed pathogen vectors like the plasmids of certain pathogenic bacteria are directly used in the transfer of recombinant DNA into the host cell. 

$$\bullet$$ They act as suitable vectors for gene cloning or the expression of the gene. 

$$\bullet$$ Restriction enzymes are used to create DNA fragments and not in DNA isolation. The separation of DNA from other macromolecules in the cell does not take place in the presence of restriction enzymes. 

$$\bullet$$ Restriction enzymes are used to create cuts in the DNA at specific recognition sites where the enzyme binds with the DNA. 

$$\bullet$$ Downstream processing is the process of separating the recombinant DNA from other macromolecules. 

$$\bullet$$ The main idea behind downstream processing is for the purification of products. In this case, the purified form of recombinant DNA can be collected separating from the other macromolecules. 

$$\bullet$$ The first transgenic cow named Rosie produced milk enriched with alpha-lactalbumin. 

$$\bullet$$ The first cloned sheep is named Dolly, which was cloned using a nuclear transfer technique. 

$$\bullet$$ Therefore both statements B and D are incorrect.

Hence, the correct answer is option (C).

• Transformation is the transfer of genetic material from one bacterial strain to another without establishing physical contact. 
• Transduction is the transfer of genetic material from one strain to other via viral particles. The virus infects bacteria and released viral particles carry part of the bacterial genetic material which is then transferred to the next host bacterium. 
• Electroporation is the method of direct gene transfer by applying a pulse of high voltage to protoplasts/cells/ tissues to make transient pores in the plasma membrane which serve to uptake the foreign DNA. 
• Conjugation is the transfer of genetic material between two bacterial strains via the conjugation tube. 
• DNA replication is semiconservative in which a DNA strand serves as a template for the synthesis of a new strand and produces two new DNA molecules, each with one new strand and one parental strand; it is not a method of gene transfer. 

• Molecular techniques are at present powerful and valuable tools for assessing the genetic stability among in vitro micropropagated plants. 
• Random amplified polymorphic DNA (RAPD) is a polymerase chain reaction (PCR) based technique widely used for the determination of the genetic fidelity of in vitro regenerated plantlets. 
• RAPD does not require prior sequence information, use a small amount of DNA, and are easy to use, thus considered to be suitable techniques for assessment of genetic fidelity of in vitro regenerated plantlets. 
• So, the correct answer is option A.

• Restriction enzymes cut double-stranded DNA at specific locations based on the pattern of bases found at those locations.
• These enzymes predictably cut both strands because the sequences they recognize are palindromic. 
• Palindrome is a segment of double-stranded DNA in which the nucleotide sequence of one strand reads in reverse order to that of the complementary strand. 
   So, the correct answer is 'Palindromic nucleotide sequence'

• Antibiotic resistance genes are commonly found on plasmids, which are small extrachromosomal elements commonly found in bacteria. 
• Plasmids can commonly move from one bacterial cell to another by a mechanism known as conjugation, which involves cell‐to‐cell contact followed by the transfer of a copy of plasmid DNA from a donor to a recipient.