The enzyme that cuts DNA, isolated in 1963, was called a restriction:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Exonuclease
• Endonuclease
• Ligase
• Polymerase
Correct Option: B  [ Endonuclease ]

Remark: The enzyme that cut DNA was called restriction endonuclease.

The first restriction endonuclease whose functioning depended on a specific DNA nucleotide sequence, isolated and characterized in 1968, was:

[Biotechnology-Principles-and-Processes] [class-xii ]

• EcoRI
• BamH I
• Hind II
• Sal I
Correct Option: C  [ Hind II ]

Remark: Hind II was the first restriction endonuclease characterized to depend on a specific DNA sequence.

Hind II always cut DNA molecules by recognising a specific sequence of how many base pairs?

[Biotechnology-Principles-and-Processes] [class-xii ]

• Four
• Five
• Six
• Eight
Correct Option: C  [ Six ]

Remark: Hind II recognizes a specific sequence of six base pairs.

How many restriction enzymes have been isolated from over 230 strains of bacteria today?

[Biotechnology-Principles-and-Processes] [class-xii ]

• Exactly 230
• Less than 500
• More than 900
• Exactly 1200
Correct Option: C  [ More than 900 ]

Remark: We know more than 900 restriction enzymes that have been isolated from over 230 strains of bacteria.

In the convention for naming restriction enzymes (e.g., *EcoRI*), the first letter comes from the:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Species
• Genus
• Strain
• Order
Correct Option: B  [ Genus ]

Remark: The first letter comes from the genus (E from Escherichia).

In the convention for naming restriction enzymes (e.g., *EcoRI*), the second two letters come from the:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Genus
• Species
• Strain
• Order
Correct Option: B  [ Species ]

Remark: The second two letters come from the species (co from coli).

In the restriction enzyme name *EcoRI*, the letter ‘R’ is derived from the name of the bacterial:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Gene region
• Species name
• Strain name
• Plasmid type
Correct Option: C  [ Strain name ]

Remark: The letter ‘R’ is derived from the name of the strain (RY 13).

The Roman numbers following the names of restriction enzymes indicate the:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Activity level
• Molecular size
• Order in which the enzymes were isolated
• Recognition site length
Correct Option: C  [ Order in which the enzymes were isolated ]

Remark: Roman numbers indicate the order in which the enzymes were isolated from that strain of bacteria.

Restriction enzymes belong to a larger class of enzymes called:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Polymerases
• Nucleases
• Ligases
• Proteases
Correct Option: B  [ Nucleases ]

Remark: Restriction enzymes belong to the larger class of enzymes called nucleases.

Exonucleases function by removing nucleotides from:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Specific positions within the DNA
• The ends of the DNA
• Specific restriction sites
• RNA molecules only
Correct Option: B  [ The ends of the DNA ]

Remark: Exonucleases remove nucleotides from the ends of the DNA.