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Q8:
Can you recall meiosis and indicate at what stage a recombinant DNA is made?
Solution :
Theoretical Foundation of Recombinant DNA Formation
Recombinant DNA (rDNA) technology involves the artificial manipulation of genetic material to combine DNA sequences from different biological sources. To address the question of "at what stage" recombination occurs in a natural biological sense—specifically regarding meiosis—we must differentiate between natural genetic recombination (crossing over) and artificial recombinant DNA technology (laboratory-based cloning).
Step 1: Defining Meiotic Recombination (Natural Process)
In biological systems, natural recombination occurs during Prophase I of meiosis, specifically within the Pachytene stage. This process involves the physical exchange of genetic material between non-sister chromatids of homologous chromosomes.
- Leptotene: Chromosomes condense.
- Zygotene: Synapsis occurs; formation of the synaptonemal complex.
- Pachytene: Crossing over occurs [Per the Law of Independent Assortment and Linkage studies].
- Diplotene: Dissolution of the synaptonemal complex, revealing chiasmata.
- Diakinesis: Terminalization of chiasmata.
Step 2: Recombinant DNA Technology (Laboratory Process)
Unlike natural meiotic recombination, laboratory-produced rDNA does not occur within a cell's division cycle. Instead, it is an in vitro biochemical process. The construction of rDNA involves the following sequential logical steps:
| Stage | Process | Mechanism |
|---|---|---|
| 1. Cleavage | Isolation of gene of interest and vector | [Utilizing Restriction Endonucleases at specific palindromic sequences] |
| 2. Ligation | Joining of DNA fragments | [Utilizing DNA Ligase to form phosphodiester bonds] |
| 3. Insertion | Transformation into host | [Per the principles of Horizontal Gene Transfer] |
Step 3: Critical Analytical Comparison
The distinction between the two is categorical:
- Meiotic Recombination: Occurs during the Pachytene stage of Prophase I. It involves the breakage and reunion of endogenous chromosomal DNA to ensure genetic diversity [Per the biological principle of Genetic Variation].
- rDNA Formation: Occurs in a laboratory environment, independent of the cell cycle. It uses in vitro enzymes to create novel sequences not found in nature.
Conclusion on Recombination Stages
While meiotic recombination (natural) is restricted to the Pachytene phase of Prophase I, Recombinant DNA (artificial) is created through in vitro enzymatic manipulation before introduction into a living host organism. One should not conflate the crossing-over event of meiosis with the molecular cloning procedures used in Biotechnology.
Final Solution: Natural genetic recombination occurs during the Pachytene stage of Prophase I in meiosis, whereas recombinant DNA technology is an in vitro process performed in a laboratory setting using restriction enzymes and DNA ligases.
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?
- 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(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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