A DNA palindrome reads the same on the two strands when the orientation of reading is kept the same, typically in the:

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

• 3' $\rightarrow$ 5' direction only
• 5' $\rightarrow$ 3' direction
• Reverse direction only
• Complementary direction
Correct Option: B  [ 5' $\rightarrow$ 3' direction ]

Remark: The palindrome in DNA is a sequence that reads same on the two strands when orientation of reading is kept the same (e.g., 5' $\rightarrow$ 3' direction).

The stickiness of the ends produced by restriction enzymes is crucial because it facilitates the action of which enzyme?

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

• DNA polymerase
• DNA ligase
• Ribonuclease
• Protease
Correct Option: B  [ DNA ligase ]

Remark: The stickiness of the ends facilitates the action of the enzyme DNA ligase to join the fragments.

The recombinant vector molecule cannot normally be created unless one cuts the vector and the source DNA with:

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

• Different restriction enzymes
• The same restriction enzyme
• Only exonucleases
• Random enzymes
Correct Option: B  [ The same restriction enzyme ]

Remark: Normally, one must cut the vector and the source DNA with the same restriction enzyme.

A high copy number plasmid vector would be preferred if the desired outcome is to recover:

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

• Fewer copies of the target DNA
• Many copies of the target DNA
• Only purified protein
• A stable, non-replicating molecule
Correct Option: B  [ Many copies of the target DNA ]

Remark: If one wants to recover many copies, the vector origin should support high copy number.

In selection using antibiotic resistance genes, the purpose of using normal *E. coli* cells (which lack resistance) is that they are useful for identifying:

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

• Recombinants
• Non-transformants
• Mutants
• Transformants
Correct Option: D  [ Transformants ]

Remark: Normal E. coli cells do not carry resistance, allowing selection of cells that have been successfully transformed (picked up the plasmid).

In the vector pBR322, the letter ‘rop’ codes for proteins involved in the:

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

• Ligation of alien DNA
• Selection process
• Replication of the plasmid
• Insertional inactivation
Correct Option: C  [ Replication of the plasmid ]

Remark: rop codes for the proteins involved in the replication of the plasmid.

The inactivation of the $\beta$-galactosidase gene in chromogenic selection is caused by the insertion of:

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

• The selectable marker
• Alien DNA
• The origin of replication
• A promoter sequence
Correct Option: B  [ Alien DNA ]

Remark: The gene is inactivated because recombinant DNA (alien DNA) is inserted within its coding sequence.

The bacterial cells must be made ‘competent’ before transformation by treating them with a divalent cation such as calcium, which primarily increases the efficiency with which DNA enters the bacteria through:

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

• Cytoplasmic fusion
• Pores in its cell wall
• Endocytosis
• Active transport mechanisms
Correct Option: B  [ Pores in its cell wall ]

Remark: Calcium increases the efficiency with which DNA enters the bacterium through pores in its cell wall.

The micro-particles used in biolistics (gene gun) methods for bombarding plant cells are coated with DNA and typically made of gold or:

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

• Platinum
• Silver
• Tungsten
• Copper
Correct Option: C  [ Tungsten ]

Remark: Cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA.

The last method mentioned for introducing alien DNA into host cells involves using ‘disarmed _________’ vectors, which infect the cell and transfer the recombinant DNA.

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

• Fungi
• Protozoa
• Pathogen
• Bacterial
Correct Option: C  [ Pathogen ]

Remark: The last method uses ‘disarmed pathogen’ vectors.