The first recombinant DNA molecule was constructed by linking a gene for antibiotic resistance with a native plasmid of which bacterium?

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

• Escherichia coli
• Salmonella typhimurium
• Agrobacterium tumifaciens
• Thermus aquaticus
Correct Option: B  [ Salmonella typhimurium ]

Remark: The construction used a native plasmid of Salmonella typhimurium.

Stanley Cohen and Herbert Boyer accomplished the construction of the first artificial recombinant DNA molecule in:

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

• 1963
• 1969
• 1972
• 1980
Correct Option: C  [ 1972 ]

Remark: Cohen and Boyer accomplished the construction of the first recombinant DNA in 1972.

The capability of cutting DNA at specific locations became possible with the discovery of the so-called:

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

• Molecular magnets
• Molecular scissors (restriction enzymes)
• DNA ligase
• DNA polymerase
Correct Option: B  [ Molecular scissors (restriction enzymes) ]

Remark: Restriction enzymes are known as ‘molecular scissors’.

Plasmid DNA acts as a _________ to transfer the piece of alien DNA attached to it into the host organism.

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

• Enzyme
• Marker
• Vector
• Substrate
Correct Option: C  [ Vector ]

Remark: Plasmid DNA acts as a vector to transfer the piece of DNA attached to it, similar to how a mosquito transfers a malarial parasite.

Which enzyme was necessary to link the antibiotic resistance gene with the plasmid vector by joining the cut DNA ends?

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

• Restriction endonuclease
• DNA ligase
• DNA polymerase
• Ribonuclease
Correct Option: B  [ DNA ligase ]

Remark: DNA ligase acts on cut DNA molecules and joins their ends, enabling the linking of the gene with the vector.

A new combination of circular autonomously replicating DNA created *in vitro* by joining cut DNA molecules is known as:

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

• Transposon
• Phage DNA
• Recombinant DNA
• Host DNA
Correct Option: C  [ Recombinant DNA ]

Remark: This new combination, created in vitro, is known as recombinant DNA.

What is the first basic step in genetically modifying an organism?

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

• Isolation of the host
• Ligation of DNA
• Identification of DNA with desirable genes
• PCR amplification
Correct Option: C  [ Identification of DNA with desirable genes ]

Remark: The first basic step is the identification of DNA with desirable genes.

The final basic step in genetically modifying an organism is maintenance of introduced DNA in the host and transfer of the DNA to its _________.

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

• Culture medium
• Progeny
• Cytoplasm
• Bioreactor
Correct Option: B  [ Progeny ]

Remark: The introduced DNA must be maintained in the host and transferred to its progeny.

Besides restriction enzymes, polymerase enzymes, and ligases, the key tools of recombinant DNA technology include vectors and the:

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

• Seaweed matrix
• Thermostable protein
• Host organism
• Chromogenic substrate
Correct Option: C  [ Host organism ]

Remark: The key tools are restriction enzymes, polymerase enzymes, ligases, vectors and the host organism.

In 1963, two enzymes were isolated responsible for restricting bacteriophage growth in *E. coli*. One cut DNA, and the other:

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

• Repaired DNA damage
• Added methyl groups to DNA
• Degraded proteins
• Synthesized RNA
Correct Option: B  [ Added methyl groups to DNA ]

Remark: One of these added methyl groups to DNA, while the other cut DNA (restriction endonuclease).