2nd PUC Biology Question and Answer: Biotechnology : Principles And Processes
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Karnataka 2nd PUC Biology Textbook Answers—Reflections Chapter 11
Biotechnology : Principles And Processes Questions and Answers, Notes, and Summary
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Question and Answer:
Question 1.
Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
Answer:
The following are recombinant proteins used in medical practice and their therapeutic applications:
- OKT-3 (Muromonab-CD3) – Used for the reversal of acute kidney transplantation rejection.
- ReoPro (Abciximab) – Used for the prevention of blood clots during coronary artery procedures.
- Tissue Plasminogen Activator (tPA) – Used for dissolving blood clots in patients with acute myocardial infarction and stroke.
- Asparaginase – Used for the treatment of certain types of cancer, especially acute lymphoblastic leukemia.
- DNase (Dornase alfa) – Used in the treatment of cystic fibrosis to reduce mucus viscosity.
- Insulin (Human recombinant insulin) – Used in the management of diabetes mellitus.
- Blood Clotting Factor VIII – Used for treating Haemophilia A (Factor VIII deficiency).
- Blood Clotting Factor IX – Used for treating Haemophilia B (Factor IX deficiency).
- Hepatitis B Vaccine (Recombinant HBsAg) – Used for the prevention of Hepatitis B infection.
- Platelet-Derived Growth Factor (PDGF) – Used for diabetic ulcers and wound healing as it promotes tissue repair.
Question 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.
Question 3.
From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
Answer:
DNA is bigger in molecular size than enzymes.
Explanation:
- Enzymes are proteins made up of a few hundred to a few thousand amino acids.
- DNA molecules are much larger, made up of millions of nucleotides.
- For example, the DNA molecule in a single human cell is about 2 meters long when stretched out.
- The difference in size can also be observed through techniques like gel electrophoresis, where DNA fragments move slower than smaller protein molecules (enzymes).
Hence, DNA is much larger than enzymes in molecular size.
Question 4.
What would be the molar concentration of human DNA in a human cell? Consult your teacher.
Answer:
Molar concentration is the ratio of the number of moles of solute in a solution to the volume of the solution (in liters).
- The average weight of a DNA base pair = 650 daltons
(1 dalton = 1.67 × 10⁻²⁴ grams) - The molecular weight of a double-stranded DNA molecule =
Total number of base pairs × 650 daltons - The human genome is 3.3 × 10⁹ base pairs in length.
Therefore,
Weight of human genome = 3.3 × 10⁹ bp × 650 Da
= 3.59 × 10⁻¹² grams
Hence, the molar concentration of DNA in a human cell can be calculated accordingly using the relation:
Since the cell volume varies, the exact molar concentration is extremely low, approximately in the nanomolar (10⁻⁹ M) range.
Question 5.
Do eukaryotic cells have restriction endonucleases? Justify your answer.
Answer:
The stirred tank bioreactor facilitates the mixing and oxygen availability. It controls the temperature and pH inside the bioreactor.
Question 6.
Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
Answer:
Shake flasks are used for growing and mixing the desired materials on a small scale in laboratories.
In contrast, bioreactors are vessels in which raw materials are biologically converted into specific products by microbes, plant or animal cells, or their enzymes.
Bioreactors are used for large-scale production of biomass or cell products under aseptic conditions. They can process large volumes (about 100–1000 litres) of culture.
A bioreactor provides optimal growth conditions such as suitable temperature, pH, substrate, salts, vitamins, and oxygen to achieve the desired product.
The most commonly used bioreactors are of the stirred-tank type.
Advantages of stirred-tank bioreactors over shake flasks:
- Equipped with an agitator system for proper mixing of contents.
- Have an oxygen delivery system to ensure adequate oxygen supply.
- Include a foam control system to manage foam formation.
- Have temperature and pH control systems for maintaining ideal growth conditions.
- Provide a sampling port to withdraw small volumes of culture periodically without contamination.
Question 7.
Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
Answer:
Question 8.
Can you recall meiosis and indicate at what stage a recombinant DNA is made?
Answer:
Meiosis I – Pachytene – When recombination nodule appears after synaptonemal complex formation.
Question 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?
Answer:
A selectable marker helps to identify and eliminate non-transformed host cells, allowing only the transformed cells containing foreign DNA to grow.
In addition to this, a reporter gene (or reporter enzyme) is used to visually or biochemically monitor the success of transformation. It expresses a detectable product (like colour, fluorescence, or luminescence), which indicates the presence and activity of the inserted foreign DNA. Thus, it provides a direct and observable confirmation of transformation along with the selectable marker.
Describe briefly the following:
(a) Origin of replication (Ori):
It is a specific sequence on the plasmid DNA where replication begins. Any DNA segment linked to this sequence can replicate within the host cell. This property is used to produce multiple copies of a desired DNA fragment within the host.
(b) Bioreactors:
Bioreactors are vessels that provide a controlled environment for biological processes, where microorganisms, plant, or animal cells synthesize desired products such as enzymes, proteins, or vaccines. Large-scale production is done using stirred-tank bioreactors, which maintain optimal conditions for growth and product formation through proper aeration, mixing, temperature, and pH control.
(c) Downstream processing:
After the product is synthesized in the bioreactor, it undergoes several steps to become a usable final product. These include separation, purification, quality control testing, and preservation. Downstream processing ensures that the final product meets required purity and safety standards before marketing.
Question 10.
Describe briefly the following:
(a) Origin of replication
(b) Bioreactors
(c) Downstream processing
(a) Origin of replication (Ori):
It is a specific sequence on the plasmid DNA where replication begins. Any DNA segment attached to this site can replicate within the host cell. This property allows scientists to make multiple copies of the desired DNA fragment within the host organism.
(b) Bioreactors:
Bioreactors are large vessels that provide a controlled environment for biological reactions, where microorganisms, plant, or animal cells produce desired products such as enzymes, proteins, or vaccines. They maintain optimal conditions like temperature, pH, aeration, and mixing for large-scale production.
(c) Downstream processing:
After the product is formed in the bioreactor, it must be separated, purified, and processed before it can be marketed. These steps—collectively known as downstream processing—also include quality control testing and storage in suitable conditions to ensure product safety and effectiveness.
Question 11.
Explain briefly
(a) PCR
(b) Restriction enzymes and DNA
(c) Chitinase
(a) PCR (Polymerase Chain Reaction):
PCR is a technique used to amplify a specific segment of DNA, producing millions of identical copies from a small DNA sample. It involves three main steps — denaturation, annealing, and extension — which are repeated in cycles using a thermostable enzyme called Taq polymerase. This method is widely used in genetic research, forensics, and medical diagnostics.
(b) Restriction enzymes and DNA:
Restriction enzymes (restriction endonucleases) are molecular scissors that cut DNA at specific sequences known as recognition sites. These enzymes help in creating recombinant DNA by cutting both vector and foreign DNA at the same site, allowing them to join and form a new DNA molecule.
(c) Chitinase:
Chitinase is an enzyme that breaks down chitin, a major component of fungal cell walls. In genetic engineering, chitinase is used to isolate DNA from fungal cells by degrading the chitin barrier, allowing easy extraction of cellular contents.
Question 12.
Discuss with your teacher and find out how to distinguish between
(a) Plasmid DNA and Chromosomal DNA
(b) RNA and DNA
(c) Exonuclease and Endonuclease
(a) Plasmid DNA and Chromosomal DNA:
Feature | Plasmid DNA | Chromosomal DNA |
Structure | Circular and double-stranded | Linear and double-stranded |
Location | Found in the cytoplasm of bacteria | Found in the nucleus (in eukaryotes) or nucleoid (in prokaryotes) |
Function | Carries non-essential but beneficial genes (e.g., antibiotic resistance) | Contains essential genes necessary for the organism’s survival |
Replication | Replicates independently of the chromosomal DNA | Replicates during cell division |
Size | Small in size | Large in size |
(b) RNA and DNA:
Feature | RNA | DNA |
Sugar | Ribose | Deoxyribose |
Bases | Adenine (A), Uracil (U), Cytosine (C), Guanine (G) | Adenine (A), Thymine (T), Cytosine (C), Guanine (G) |
Strands | Usually single-stranded | Double-stranded |
Stability | Less stable | More stable |
Function | Helps in protein synthesis and gene expression | Stores genetic information |
(c) Exonuclease and Endonuclease:
Feature | Exonuclease | Endonuclease |
Action Site | Removes nucleotides from the ends of DNA strands | Cuts DNA at specific internal sites within the strand |
Type of Cut | Sequentially from ends (5’ or 3’) | Within the sequence at specific recognition sites |
Example | Exonuclease I | EcoRI, HindIII |
Use in Biotechnology | Used in DNA repair and degradation | Used in gene cloning and recombinant DNA formation |
Additional Questions and Answers
Question 1.
What are cloning vectors? Give examples.
Answer:
Cloning vectors are DNA molecules that carry a foreign DNA fragment into a host cell where it can replicate.
Examples include plasmids, bacteriophages (λ phage), and cosmids.
An ideal cloning vector must have:
- Origin of replication (Ori)
- Selectable marker genes
- Cloning sites for restriction enzymes
Question 2.
What is recombinant DNA technology?
Answer:
Recombinant DNA technology involves joining together DNA molecules from two different sources and inserting them into a host organism to produce new genetic combinations that are of value in research, medicine, and industry.
Question 3.
Name the enzymes used in recombinant DNA technology and mention their functions.
Answer:
- Restriction enzymes – Cut DNA at specific sites.
- Ligases – Join DNA fragments together.
- Polymerases – Synthesize DNA or RNA strands.
- Reverse transcriptase – Synthesizes DNA from RNA.
- Chitinase – Breaks down fungal cell walls to extract DNA.
Question 16.
What is a selectable marker? Why is it used in cloning?
Answer:
A selectable marker is a gene introduced into a cell that confers a trait suitable for artificial selection.
Example: Ampicillin resistance (ampR) and tetracycline resistance (tetR) genes in plasmid pBR322.
They help in identifying the transformed cells from the non-transformed ones.
Question 17.
What is the role of calcium ions in bacterial transformation?
Answer:
Calcium ions help in making the bacterial cell membrane permeable, allowing the uptake of recombinant DNA into E. coli cells.
Question 18.
What is gel electrophoresis and what is its purpose?
Answer:
Gel electrophoresis is a technique used to separate DNA fragments based on their size and charge by applying an electric current through agarose gel.
Smaller fragments move faster toward the positive electrode.
Question 19.
What are the basic steps involved in genetic engineering?
Answer:
- Isolation of genetic material (DNA)
- Cutting of DNA at specific locations using restriction enzymes
- Ligation of DNA into vector
- Insertion of recombinant DNA into host
- Selection and screening of transformed cells
- Expression and purification of desired product
Question 20.
What is the role of plasmids in genetic engineering?
Answer:
Plasmids act as vectors to transfer foreign genes into host organisms, ensuring replication and expression of the inserted gene.