NCERT Solutions

• Source: Escherichia coli RY 13.
• Substrate DNA: Double stranded DNA containing the palindrome sequence GAATTC.
• Recognition Site:
  5′ – G A A T T C – 3′
  3′ – C T T A A G – 5′
• Cutting Site: Between G and A on both strands.
• Product: DNA fragments with Sticky Ends (overhanging single strands).

DNA is bigger than enzymes in molecular size.

• Enzymes are proteins made of amino acids. An average protein consists of a few hundred to a few thousand amino acids.
• DNA is a polymer of nucleotides. Even a small DNA molecule (like a plasmid) has thousands of base pairs. Genomic DNA has millions to billions of base pairs (e.g., Human DNA has \(3.3 \times 10^9\) bp).
• The molecular weight of DNA is significantly higher than that of proteins.

• Total number of chromosomes in a human cell (diploid) = 46.
• Total number of base pairs \(\approx 6.6 \times 10^9\).
• Molar concentration varies based on the volume of the cell/nucleus. If we consider the molar mass of 1 bp \(\approx 660\) g/mol, the molar concentration of DNA is extremely low in terms of Molarity, but high in terms of mass/volume within the nucleus.

No, eukaryotic cells typically do not have restriction endonucleases.

• Restriction endonucleases are part of the bacterial defense system (Restriction-Modification System) to destroy foreign viral DNA (bacteriophages).
• Eukaryotic cells have different defense mechanisms (like immune systems, RNA interference) and do not methylated their own DNA in the specific patterns required to protect against their own restriction enzymes.

• Volume: Bioreactors handle large volumes (100-1000 liters) compared to small volumes in shake flasks.
• Control Systems: They have automated control systems for Temperature, pH, and Foam regulation.
• Continuous Culture: They allow for continuous addition of nutrients and withdrawal of products (Continuous culture system), maintaining cells in the exponential phase.
• Sampling Port: Allows withdrawing small volumes of culture periodically for testing without contaminating the whole batch.

A palindrome in DNA is a sequence of base pairs that reads the same on the two strands when orientation of reading is kept the same (e.g., 5′ \(\to\) 3′).

Recombinant DNA is naturally formed during Meiosis I.

• Stage: Pachytene stage of Prophase I.
• Process: Crossing Over occurs between non-sister chromatids of homologous chromosomes. This exchange of genetic material results in recombination.

• A Reporter Enzyme (like \(\beta\)-galactosidase encoded by lacZ gene) produces a visible change (usually color) when the substrate is present.
• Insertional Inactivation: If foreign DNA is inserted within the coding sequence of the reporter enzyme, the enzyme is inactivated.
• Monitoring:
  • Non-recombinants: Enzyme is active. Colonies appear Blue in presence of chromogenic substrate (X-gal).
  • Recombinants: Enzyme is inactive (Insertional Inactivation). Colonies appear White.
• This allows easy differentiation of recombinant colonies from non-recombinant ones.

It is a specific DNA sequence where replication initiates. Any piece of DNA linked to this sequence can be made to replicate within the host cells. It also controls the copy number of the linked DNA.

Large vessels (100-1000 litres) used for the biological conversion of raw materials into specific products (enzymes, proteins) using microbial, plant, or animal cells. They provide optimal conditions (temp, pH, substrate, salts, vitamins, oxygen) for growth.

The series of processes a product undergoes after the biosynthetic stage (fermentation) before it is marketed. It includes Separation and Purification. The product is then formulated with preservatives and undergoes clinical trials.

A technique to amplify a specific DNA sequence in vitro. Steps:

1. Denaturation: Heating (94°C) to separate DNA strands.
2. Annealing: Primers bind to complementary sequences (54°C).
3. Extension: Taq polymerase extends the primers using nucleotides (72°C).

Restriction enzymes (Molecular Scissors) cut DNA at specific palindromic sequences. They create sticky ends which facilitate the joining of foreign DNA with vector DNA using DNA ligase.

An enzyme used to break down the cell wall of Fungi (which is made of Chitin) to isolate DNA during the process of genetic engineering.