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: 10 recombinant proteins used in medical practice along with their therapeutic value are as follows:
| Protein |
Therapeutic Value |
| Growth Hormone |
Promoting growth in an individual |
| Human Insulin |
Treatment for type I diabetes mellitus |
| Erythropoietin |
Treatment of anaemia during renal failure |
| Follicle-stimulating hormone |
Stimulation of ovarian follicle growth |
| Interferon α |
Treatment of chronic Hepatitis C |
| Insulin-like growth factor |
Dwarfism |
| Tissue Plasminogen Activator |
Thrombosis |
| Blood clotting Factor VIII |
Haemophilia |
| DNase I |
Treatment of cystic fibrosis |
| Interferon β |
Treatment of multiple sclerosis |
Q. 2) What would be the molar concentration of human DNA in a human cell? Consult your teacher.
Ans: Molar concentration is the concentration measured by the number of moles of solute per litre of solution. The number of moles of human DNA in a human diploid cell will be calculated as follows:
Total number of chromosomes × 6.023 × 1023
= 46 × 6.023 × 1023
= 2.77 × 1025 moles
However, since the volume of solute in each cell varies depending upon the shape, size and type, one cannot calculate the molar concentration of DNA in each human cell.
Q. 3) Do eukaryotic cells have restriction endonucleases? Justify your answer.
Ans: No, eukaryotic cells do not have restriction endonucleases.
Justification: Restriction endonucleases are enzymes present in bacteria that restrict the growth of bacteriophages by cutting DNA at or near a specific recognition nucleotide sequence called restriction site. They act as self-defence mechanisms of bacteria. The bacterial host DNA is protected due to modifications like methylation.
Eukaryotic cells have other endonucleases such as topoisomerase which help in releasing the tension of supercoiled DNA during replication.
Q. 4) Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
Ans: Besides better aeration and mixing properties, the advantages of stirred tank bioreactors are:
- Air or oxygen can be bubbled in a controlled manner.
- Foam control system breaks excess foam.
- Temperature control system maintains desired temperature.
- pH control system maintains desired pH.
- Sampling ports allow periodic testing.
Q. 5) Write 5 examples of palindromic DNA sequence by following base pair rules.
Ans: Some examples of palindromic DNA sequences are:
1. EcoRI
5’ – GAATTC – 3’
3’ – CTTAAG – 5’
2. BamHI
5’ – GGATCC – 3’
3’ – CCTAGG – 5’
3. HindIII
5’ – AAGCTT – 3’
3’ – TTCGAA – 5’
4. PstI
5’ – CTGCAG – 3’
3’ – GACGTC – 5’
5. EcoRV
5’ – GATATC – 3’
3’ – CTATAG – 5’
Q. 6) Can you recall meiosis and indicate at what stage a recombinant DNA is made?
Ans: Crossing over occurs during the pachytene stage of Prophase I of meiosis I. Hence, recombinant DNA is formed during the pachytene stage.
Q. 7) Can you think about how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA?
Ans: Reporter genes confer identifiable properties in transformed cells. β-galactosidase is commonly used. Recombinant cells form white colonies due to insertional inactivation, whereas non-recombinant cells form blue colonies.
Q. 8) Describe briefly:
1. Origin of replication: A specific DNA sequence where replication begins. Foreign DNA linked to it can replicate inside host cells.
2. Bioreactors: Large vessels used for mass production of recombinant proteins under controlled conditions.
3. Downstream processing: Recovery, purification and quality control of biosynthetic products.
Q. 9) Explain briefly:
1. PCR: Polymerase Chain Reaction amplifies DNA using Taq polymerase through denaturation, annealing and extension steps.
2. Restriction enzymes: Enzymes that cut DNA at specific recognition sequences.
3. Chitinase: Enzyme used to digest fungal cell walls.
Q. 10) Distinguish between:
a. Plasmid DNA and Chromosomal DNA
Plasmid DNA is extra-chromosomal and circular, while chromosomal DNA is the main genetic material.
b. RNA and DNA
RNA has ribose and uracil; DNA has deoxyribose and thymine.
c. Exonuclease and Endonuclease
Exonucleases cut DNA from ends; endonucleases cut within the DNA.
Q. 11) Are enzymes bigger or DNA bigger in molecular size? How did you know?
Ans: DNA is bigger in molecular size because it stores entire genetic information coding for many proteins.
Q. 12) Make a chart showing restriction enzyme action.
Ans: (Diagram-based answer as given in NCERT)