NCERT Class 12 Biology Chapter 11 Principles and Process in Biotechnology

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NCERT Class 12 Biology Chapter 11 Principles and Process in Biotechnology

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Principles and Process in Biotechnology

Chapter: 11

BIOLOGY

UNIT – IV BIOTECHNOLOGY AND ITS APPLICATIONS

TEXT BOOK QUESTIONS ANSWERS

Q. 1. Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet). 

Ans:

Q. 2. Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.

Ans: Eco R I is isolated from Escherichia coli RY 13. It recognises the base sequence GAATTC in DNA duplex and cuts its strands between G and A. It produces sticky ends.

Q. 3. From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How Did you know?

Ans: DNA is bigger in molecular size because DNA polymers have million of nucleotides.

Q. 4. What would be the molar concentration of human DNA in a human cell? Consult your teacher.

Ans: Molar concentration of human DNAin a human diploid cell = Total no of human chromosome in human cell × 6.023 × 10²³ = 46 × 6.023 × 1023 = 2.77 × 10¹⁸ moles.

Q. 5. Do eukaryotic cells have restriction endonucleases? Justify your answer.

Ans: Eukaryotic cells do not have restriction endonucleases. Restriction enzymes are present in prokaryotes to prevent infection viruses by cutting viral DNA.

Q. 6. Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?

Ans. It is used in processing of large scale production (100-1000 liters) of culture. It Provides optimum growth conditions (temperature, pH, substrate, salts, vitamins,oxygen).

Q. 7. Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base pair rules.

Ans: Following sequences reads the same on the two strands in 5′ → 3 direction and 3’→ 5′ direction.

5′ ― GAATTC ― 3′

3′ ― CTTAAG ― 5′

Q. 8. Can you recall meiosis and indicate at what stage a recombinantDNA is made?

Ans: Recombinant DNA is made atPachytene stage in Prophase I of Meiosis I.

Q. 9. Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?

Ans: Insertional inactivation

(i) Recombinant DNA is inserted within the coding sequence of an enzyme, β- galactosidase which causes inactivation of the enzyme. This is called insertional inactivation.

(ii) Recombinants and non-recombinants can be differentiated on the basis of color production with chromogenic substrate.

(iii) Presence of inserted plasmid causes insertional inactivation of a galactosidase and recombinants colonies do not produce any color.

(iv) Non recombinant colonies [colonies without inserted plasmid] form blue coloured colonies.

Q. 10. Describe briefly the followings:

(a) Origin of replication.

Ans: Origin of replication: Ori is specific sequence of DNA bases which is responsible for initiating replication. 

(b) Bioreactors.

Ans: Bioreactors are vessels in which raw materials are biologically converted into specific products using microbes, plant, animal or human cells. It is used in processing of large scale production (100-1000 liters) of culture. It provides optimum growth conditions. (temperature, pH, substrate, salts, vitamins. oxygen). Most commonly used bioreactors are Stirred-tank reactor.

(c) Downstream processing.

Ans: Downstream processing: Separation and purification of the products of bioreactors is called downstream processing. The product is subjected to quality control testing and formulated with suitable preservatives.

Q. 11. Explain briefly:

(a) PCR.

Ans: PCR: Polymerase Chain Reaction is defined as DNA replication in vitro which results in amplification of specific sequences of DNA. It is used to generate DNA fragments for cloning or amplification of desirable gene. Thermostable DNA polymerase (Taq polymerase isolated from a bacterium, Thermus aquaticus) is used in PCR. Each cycle has three steps:

1. Denaturation.

2. Annealing.

3. Extension of primers.

All these steps are repeated many times to get several copies of desired DNA segment.

(b) Restriction enzymes and DNA.

Ans: Restriction enzymes and DNA: Restriction endonuclease binds to specific recognition nucleotide sequence called palindromic sequences of DNA and cut them. This leaves single stranded unpaired bases at cut ends on each strand known as sticky ends. Sticky ends form hydrogen bonds with their complementary cut strands and facilitate the action of the enzyme DNA ligase. Restriction endonuclease is used in genetic engineering to form recombinant DNA made of DNA from different sources/genomes.

(c) Chitinase.

Ans: Chitinase: Isolation of the Genetic Material (DNA) is done by treating fungal cells with enzyme chitinase to release DNA, RNA and proteins.

Q. 12. Discuss with your teacher and find out how to distinguish between:

(a) Plasmid DNA and Chromosomal DNA.

Ans: Plasmid DNA and Chromosomal DNA: Plasmid is self replicating circular extra chromosomal DNA molecule present in bacterial cell. Chromosomal DNA has double-helix structure made of two polynucleotide chains with backbone of sugar-phosphate groups and nitrogen bases project inside. The two chains have antiparallel polarity i.e. 5′ → 3′ in one and 3′ → 5′ in other chain.

(b) RNA and DNA.

Ans: RNA and DNA:

(c) Exonuclease and Endonuclease.

Ans: Exonuclease and endonucleases: Exonucleases remove nucleotides from terminal ends of DNA while Endonucleases make cuts at specific positions within the DNA.