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Q10(a):
Describe briefly the following:
(a) Origin of replication
Solution :
1. Conceptual Definition: Origin of Replication (ori)
The Origin of Replication ($ori$) is a specific DNA sequence located within the genome where the process of DNA replication is initiated. This sequence acts as a recognition site for the assembly of the replication machinery, known as the replisome, which includes enzymes such as DNA helicase and DNA polymerase [Per the Watson-Crick Model of DNA replication].
2. Biochemical and Functional Properties
The $ori$ sequence is characterized by several critical features that facilitate the separation of the DNA double helix:
- Sequence Specificity: It is typically rich in Adenine-Thymine ($A=T$) base pairs. Since $A=T$ base pairs are held together by only two hydrogen bonds (compared to three in $G \equiv C$), they require less energy to destabilize and melt [Per the principles of thermodynamic stability of DNA].
- Initiator Protein Binding: The site serves as the docking station for initiator proteins (e.g., DnaA in E. coli), which induce the local unwinding of the DNA strands to create a replication bubble.
- Control of Copy Number: The $ori$ is the primary determinant of the plasmid copy number in recombinant DNA technology. If a foreign DNA fragment is ligated to a vector, that vector must possess a functional $ori$ to ensure the autonomous replication of the recombinant DNA within the host cell.
3. Visual Representation: The Replication Bubble
4. Role in Biotechnology
In the context of genetic engineering, the $ori$ is an indispensable vector component. Its functional requirements include:
| Feature | Biological Implication |
|---|---|
| Autonomous Replication | Allows the plasmid to replicate independently of the host chromosomal DNA. |
| Copy Number Control | Determines how many copies of the gene of interest are produced per host cell, directly affecting the yield of the target protein or DNA product. |
Final Solution: The Origin of Replication ($ori$) is a specific nucleotide sequence that serves as the mandatory starting point for DNA replication; it facilitates the localized unwinding of DNA and controls the copy number of recombinant plasmids within a host cell, making it an essential prerequisite for successful cloning and gene expression.
More Questions from Class 12 Biology Biotechnology: Principles and Processes EXERCISES
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q1: Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).
- Q2: 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.
- Q2: 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.
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q3: From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q4: What would be the molar concentration of human DNA in a human cell? Consult your teacher.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q5: Do eukaryotic cells have restriction endonucleases? Justify your answer.
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q6: Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q7: Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q8: Can you recall meiosis and indicate at what stage a recombinant DNA is made?
- Q9: 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?
- Q9: 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?
- Q10(a): Describe briefly the following: (a) Origin of replication
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(b): Describe briefly the following: (b) Bioreactors
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q10(c): Describe briefly the following: (c) Downstream processing
- Q11(a): Explain briefly (a) PCR
- Q11(a): Explain briefly (a) PCR
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(b): Explain briefly (b) Restriction enzymes and DNA
- Q11(c): Explain briefly (c) Chitinase
- Q11(c): Explain briefly (c) Chitinase
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(a): Discuss with your teacher and find out how to distinguish between (a) Plasmid DNA and Chromosomal DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(b): Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
- Q12(c): Discuss with your teacher and find out how to distinguish between (c) Exonuclease and Endonuclease
CBSE Solutions for Class 12 Biology Biotechnology: Principles and Processes
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Human Health and Disease
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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