biology : class12 Restriction Endonucleases : DNA Isolation, Restriction Enzymes, Vector, Ligation, Host Cell : Recombinant DNA Technology MCQ Questions and Answers
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Restriction Endonucleases
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MCQ Questions
1. What is the primary function of a restriction endonuclease?
A.
To cut DNA at specific recognition sites
B.
To join two DNA fragments
C.
To make RNA from DNA
D.
To copy the entire DNA molecule
Correct Answer:
To cut DNA at specific recognition sites
Explanation:
Restriction endonucleases recognize specific DNA sequences and cut the DNA at or near those sites.
2. Restriction endonucleases are naturally produced by which organisms?
A.
Bacteria
B.
Viruses only
C.
Plants only
D.
Animals only
Correct Answer:
Bacteria
Explanation:
Restriction endonucleases are bacterial enzymes that help protect bacteria from foreign DNA, such as viral DNA.
3. The specific DNA sequence recognized by a restriction endonuclease is called a:
A.
Recognition sequence
B.
Start codon
C.
Promoter sequence
D.
Terminator sequence
Correct Answer:
Recognition sequence
Explanation:
A restriction endonuclease identifies and binds to a particular DNA sequence known as its recognition sequence.
4. Which type of DNA sequence is commonly recognized by restriction endonucleases?
A.
Palindromic sequence
B.
Random sequence
C.
Only a protein-coding sequence
D.
Only a repeated RNA sequence
Correct Answer:
Palindromic sequence
Explanation:
Many restriction endonucleases recognize palindromic DNA sequences, which read the same in the 5′ to 3′ direction on both strands.
5. Which restriction endonuclease is commonly used to recognize the sequence GAATTC?
A.
EcoRI
B.
HindIII
C.
BamHI
D.
PstI
Correct Answer:
EcoRI
Explanation:
EcoRI recognizes the palindromic sequence GAATTC and cuts DNA within this recognition site.
6. What type of DNA ends are produced when a restriction endonuclease makes staggered cuts?
A.
Sticky ends
B.
Blunt ends only
C.
Circular ends
D.
Protein ends
Correct Answer:
Sticky ends
Explanation:
Staggered cuts create short single-stranded overhangs called sticky ends.
7. What type of ends are produced when both DNA strands are cut at the same position?
A.
Blunt ends
B.
Sticky ends
C.
Looped ends
D.
Branched ends
Correct Answer:
Blunt ends
Explanation:
A restriction endonuclease produces blunt ends when it cuts both DNA strands at the same position.
8. The name EcoRI is derived mainly from the bacterium Escherichia coli and its:
A.
Strain and enzyme order
B.
Cell size and shape
C.
Nutritional requirement and age
D.
DNA length and base composition
Correct Answer:
Strain and enzyme order
Explanation:
In EcoRI, E refers to Escherichia, co refers to coli, and RI indicates the bacterial strain and the order in which the enzyme was identified.
9. Restriction endonucleases cut DNA by breaking which bonds in the DNA backbone?
A.
Phosphodiester bonds
B.
Peptide bonds
C.
Hydrogen bonds in proteins
D.
Glycosidic bonds in amino acids
Correct Answer:
Phosphodiester bonds
Explanation:
Restriction endonucleases cleave the phosphodiester bonds that connect nucleotides in the DNA backbone.
10. What is the meaning of the term 'restriction' in restriction endonuclease?
A.
Restriction of foreign DNA in a bacterial cell
B.
Restriction of protein synthesis in animals
C.
Restriction of RNA formation in plants
D.
Restriction of cell division in fungi
Correct Answer:
Restriction of foreign DNA in a bacterial cell
Explanation:
These enzymes restrict the growth of certain bacteriophages by cutting their foreign DNA inside bacterial cells.
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