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).

Accepted Answer

Recombinant proteins used in medical practice include:
1. Insulin - used for diabetes treatment.
2. Human Growth Hormone (HGH) - used for growth disorders.
3. Erythropoietin - used to treat anemia.
4. Tissue Plasminogen Activator (tPA) - used to dissolve blood clots.
5. Interferons - used for viral infections and cancer.
6. Factor VIII - used for hemophilia.
7. Monoclonal antibodies (e.g., Rituximab) - used in cancer and autoimmune diseases.
8. Vaccines (e.g., Hepatitis B vaccine) - used for immunization.
9. Granulocyte Colony Stimulating Factor (G-CSF) - used to stimulate white blood cell production.
10. Botulinum toxin - used for muscle spasticity and cosmetic treatments.
These proteins are produced by inserting the gene encoding the protein into host cells (like bacteria or yeast) and harvesting the protein for therapeutic use. — Recombinant proteins are produced by genetic engineering techniques where the gene coding for the desired protein is cloned into an expression system. These proteins are then purified and used as therapeutics to treat various diseases. The list above includes commonly used recombinant proteins and their medical applications.

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.

Accepted Answer

Example chart:

| Restriction Enzyme | Substrate DNA Sequence | Recognition Site | Cut Site | Product |
|--------------------|-----------------------|------------------|----------|---------|
| EcoRI              | 5' GAATTC 3'           | GAATTC           | Between G and A | Sticky ends with 5' overhangs |

Diagrammatic representation:

5' - G A A T T C - 3'
3' - C T T A A G - 5'

EcoRI cuts between G and A:

5' - G ↓ A A T T C - 3'
3' - C T T A A ↑ G - 5'

Resulting in sticky ends:

5' - G    3'
     A A T T C - 5'

This shows how the enzyme recognizes a specific palindromic sequence and cuts DNA producing sticky ends useful for cloning. — Restriction enzymes recognize specific palindromic sequences in DNA and cut at precise locations. The substrate DNA contains the recognition site. The enzyme cuts the DNA producing fragments with either sticky or blunt ends. This property is exploited in recombinant DNA technology.

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?

Accepted Answer

DNA molecules are generally much larger than enzymes in molecular size. For example, the human genome consists of billions of base pairs forming very large DNA molecules, whereas enzymes are proteins made up of a few hundred to a few thousand amino acids.

This is known because DNA molecules can be several million Daltons in size, while enzymes typically range from tens to hundreds of kilodaltons. Gel electrophoresis and molecular weight measurements confirm this size difference. — DNA molecules, especially chromosomal DNA, are very large polymers of nucleotides, whereas enzymes are comparatively smaller protein molecules. Experimental techniques such as gel electrophoresis and ultracentrifugation help determine molecular sizes, showing DNA is larger.

Question 4

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

Accepted Answer

The molar concentration of human DNA in a human cell can be estimated as follows:

- The human diploid genome size is approximately 6.4 billion base pairs.
- Molecular weight of 1 base pair ≈ 660 g/mol.
- Total molecular weight of DNA per cell = 6.4 × 10^9 bp × 660 g/mol = 4.224 × 10^12 g/mol.

Since this is per cell, to find molar concentration, one would need the volume of the nucleus or cell.

Assuming nuclear volume ~ 10^-12 L (1 picoliter),

Molar concentration = moles / volume

Number of moles of DNA per cell = (mass of DNA) / (molecular weight)

But since mass is not given, this is a conceptual question to be discussed with the teacher for precise calculation.

Hence, the molar concentration is very low but significant within the nucleus. — Calculating molar concentration requires knowledge of DNA amount and volume. The human genome size and base pair molecular weight help estimate DNA mass. Volume of the nucleus is needed to calculate concentration. This question encourages consultation and understanding of molecular biology concepts.

Question 5

Do eukaryotic cells have restriction endonucleases? Justify your answer.

Accepted Answer

Eukaryotic cells generally do not have restriction endonucleases like those found in bacteria. Restriction enzymes are part of bacterial defense mechanisms against invading viral DNA.

Eukaryotes have other mechanisms for DNA repair and defense but do not possess classical restriction endonucleases. Therefore, restriction enzymes are mostly bacterial in origin and are used as tools in molecular biology. — Restriction endonucleases evolved in bacteria to protect against phage infection by cutting foreign DNA. Eukaryotic cells have evolved different DNA repair and defense systems and do not have these enzymes naturally.

Question 6

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

Accepted Answer

Advantages of stirred tank bioreactors over shake flasks include:
- Controlled environment: temperature, pH, dissolved oxygen can be precisely regulated.
- Scalability: can be used for large scale production.
- Sterility: better control to prevent contamination.
- Automation: process parameters can be monitored and controlled automatically.
- Uniform nutrient distribution and oxygen transfer.
- Ability to add feed or remove products during fermentation.

These features make stirred tank bioreactors suitable for industrial scale bioprocessing compared to shake flasks which are limited to small scale and less control. — Stirred tank bioreactors provide a controlled and scalable environment for microbial or cell culture growth, unlike shake flasks which are simple and limited in control and volume. This allows for higher yields and reproducibility in biotechnological processes.

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.

Accepted Answer

Examples of palindromic DNA sequences:
1. GAATTC (EcoRI recognition site)
2. GGATCC (BamHI recognition site)
3. AAGCTT (HindIII recognition site)
4. GCGGCCGC (NotI recognition site)
5. CCGCGG (SacII recognition site)

A palindromic sequence reads the same 5' to 3' on one strand and 5' to 3' on the complementary strand.

Example created sequence:
5' - TTAATTAA - 3'
3' - AATTAATT - 5'

This sequence is palindromic because the complementary strand reads the same in the opposite direction. — Palindromic sequences are symmetrical sequences recognized by restriction enzymes. They are important in molecular cloning. Creating such sequences involves ensuring the sequence on one strand matches the complementary strand in reverse order.

Question 8

Can you recall meiosis and indicate at what stage a recombinant DNA is made?

Accepted Answer

Recombinant DNA is formed during Prophase I of meiosis, specifically in the pachytene stage.

During this stage, homologous chromosomes pair up and crossing over occurs where segments of DNA are exchanged between non-sister chromatids, resulting in genetic recombination.

This process increases genetic diversity in gametes. — Meiosis involves pairing of homologous chromosomes and exchange of genetic material (crossing over) during Prophase I. This recombination creates new allele combinations, which is the biological basis of recombinant DNA formation in meiosis.

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?

Accepted Answer

A reporter enzyme, such as β-galactosidase (lacZ) or Green Fluorescent Protein (GFP), can be used to monitor transformation by producing a detectable signal.

When foreign DNA is successfully introduced into host cells, the reporter gene is expressed, producing an enzyme or protein that can be easily detected (e.g., color change, fluorescence).

This allows researchers to visually confirm transformation events in addition to selecting transformed cells using selectable markers like antibiotic resistance. — Reporter enzymes provide a visual or measurable output indicating successful uptake and expression of foreign DNA. This complements selectable markers which only allow growth of transformed cells but do not provide direct evidence of gene expression.

Question 10

Describe briefly the following:
(a) Origin of replication
(b) Bioreactors
(c) Downstream processing

Accepted Answer

(a) Origin of replication: A specific sequence in a genome at which DNA replication begins. It is recognized by replication proteins to initiate DNA synthesis.

(b) Bioreactors: Vessels or containers designed to provide controlled environmental conditions for the growth of microorganisms or cells to produce biological products.

(c) Downstream processing: The series of operations involved in the recovery and purification of biosynthetic products, especially pharmaceuticals, from fermentation broth or cell cultures. — Each term is fundamental in biotechnology:
- Origin of replication is crucial for DNA replication.
- Bioreactors enable large scale culture growth.
- Downstream processing ensures product purity and quality.

Question 11

Explain briefly
(a) PCR
(b) Restriction enzymes and DNA
(c) Chitinase

Accepted Answer

(a) PCR (Polymerase Chain Reaction): A technique used to amplify specific DNA sequences exponentially using cycles of denaturation, annealing of primers, and extension by DNA polymerase.

(b) Restriction enzymes and DNA: Restriction enzymes are proteins that recognize specific palindromic sequences in DNA and cut the DNA at or near these sites, producing fragments useful in genetic engineering.

(c) Chitinase: An enzyme that breaks down chitin, a polysaccharide found in fungal cell walls and exoskeletons of insects, used in biocontrol and biotechnology. — These are key concepts:
- PCR allows DNA amplification.
- Restriction enzymes enable DNA manipulation.
- Chitinase has applications in agriculture and biotechnology.

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

Accepted Answer

(a) Plasmid DNA vs Chromosomal DNA:
- Plasmid DNA is circular, smaller, and extrachromosomal.
- Chromosomal DNA is linear (in eukaryotes), larger, and contains essential genes.

(b) RNA vs DNA:
- RNA is usually single-stranded, contains ribose sugar, and uracil instead of thymine.
- DNA is double-stranded, contains deoxyribose sugar, and thymine.

(c) Exonuclease vs Endonuclease:
- Exonucleases remove nucleotides from the ends of DNA strands.
- Endonucleases cut DNA at internal sites within the strand. — These distinctions are fundamental in molecular biology:
- Plasmids are extra-chromosomal genetic elements.
- RNA and DNA differ in structure and function.
- Nucleases differ in their cleavage sites on nucleic acids.

Question 13

Which of the following best defines biotechnology according to the European Federation of Biotechnology (EFB)?

Accepted Answer

The integration of natural sciences and organisms, cells, parts thereof, and molecular analogues for products and services — The European Federation of Biotechnology defines biotechnology as the integration of natural sciences and organisms, cells, parts thereof, and molecular analogues for products and services, encompassing both traditional and modern molecular biotechnology.

Question 14

Which two core techniques form the basis of modern biotechnology?

Accepted Answer

Genetic engineering and bioprocess engineering — Modern biotechnology primarily relies on genetic engineering, which alters genetic material to change organism traits, and bioprocess engineering, which maintains sterile conditions for large-scale production of biotechnological products.

Question 15

What is the role of the origin of replication in recombinant DNA technology?

Accepted Answer

It initiates replication allowing DNA multiplication — The origin of replication is a specific DNA sequence where replication begins, enabling the introduced alien DNA to replicate and be inherited in the host organism.

Ever since the days of Rene Descartes, the French philosopher

Ever since the days of Rene Descartes, the French philosopher — Study Notes

Introduction to Biotechnology

9.1 Principles of Biotechnology

9.2 Tools of Recombinant DNA Technology

Practice Questions — Ever since the days of Rene Descartes, the French philosopher

All 13 Chapters in Biology