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Assertion (A):
Stirred-tank bioreactors are preferred over small volume cultures for protein production.
Reason (R):
Small volume cultures cannot yield appreciable quantities of products, while bioreactors handle large volumes (100–1000 litres) and optimize growth conditions.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
Micro-injection is the method used for introducing alien DNA into plant cells by bombarding them with high velocity micro-particles.
Reason (R):
Biolistics, or gene gun, is a method where recombinant DNA is directly injected into the nucleus of an animal cell.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
The construction of the first recombinant DNA involved linking an antibiotic resistance gene with a native plasmid of Salmonella typhimurium.
Reason (R):
When this recombinant DNA was transferred into Escherichia coli, it replicated using the new host’s DNA polymerase enzyme and made multiple copies (cloning).
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
For effective creation of a recombinant DNA molecule, the vector DNA and the source DNA should normally be cut with the same restriction enzyme.
Reason (R):
Cutting both DNAs with the same restriction enzyme ensures that the resultant fragments have compatible sticky ends, which facilitates the action of DNA ligase.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
The procedure for forcing recombinant DNA into competent bacterial cells involves incubating the cells on ice, followed by a brief exposure to $42^circ ext{C}$ (heat shock), and then placing them back on ice.
Reason (R):
This heat shock procedure is necessary because DNA is a hydrophobic molecule, and this chemical manipulation helps it pass through the cell membranes.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
A DNA palindrome is a sequence of base pairs that reads the same on the two strands when the orientation of reading is kept the same (e.g., $5'\ o 3'$).
Reason (R):
The word "MALAYALAM" is used as an example because it demonstrates how a word palindrome reads the same when read both forward and backward.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
Restriction enzymes are generally classified into exonucleases and endonucleases based on where they cut the DNA strand.
Reason (R):
Endonucleases remove nucleotides from the ends of the DNA, while exonucleases make cuts at specific positions within the DNA.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
If any protein encoding gene is expressed in a heterologous host, the resulting protein is called a recombinant protein.
Reason (R):
Small volume cultures in the laboratory are generally capable of yielding appreciable quantities of the desired recombinant product, making bioreactors unnecessary for scale-up.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
Continuous culture systems are employed for large-scale production in bioreactors.
Reason (R):
This type of culturing method maintains the cells in their physiologically most active log/exponential phase, leading to higher yields of desired protein.
[Biotechnology-Principles-and-Processes] [class-xii ]
Assertion (A):
The two core techniques that enabled the birth of modern biotechnology are genetic engineering and bioprocess engineering.
Reason (R):
Biotechnology products have brought qualitative improvement in health and food production.
[Biotechnology-Principles-and-Processes] [class-xii ]
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