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Q8:
Can you recall meiosis and indicate at what stage a recombinant DNA is made?
Solution :
Biological Context: Meiosis and Genetic Recombination
In biological systems, genetic recombination is a fundamental process where genetic material is exchanged between homologous chromosomes. To answer the question of when recombinant DNA is formed during meiosis, we must look at the specific stage of Prophase I.
Step 1: Stages of Meiosis I
Meiosis I consists of four primary phases: Prophase I, Metaphase I, Anaphase I, and Telophase I. Prophase I is further subdivided into five distinct stages based on morphological changes in chromosomes [Per the Cytological Theory of Meiosis]:
- Leptotene: Chromatin condenses into visible chromosomes.
- Zygotene: Pairing of homologous chromosomes occurs (synapsis) to form bivalents or tetrads.
- Pachytene: The stage where physical exchange of segments occurs.
- Diplotene: Dissolution of the synaptonemal complex begins; chiasmata become visible.
- Diakinesis: Terminalization of chiasmata.
Step 2: Identifying the Recombination Stage
Recombinant DNA, in the context of natural biological processes, is formed during the Pachytene stage of Prophase I. During this stage, the phenomenon known as Crossing Over takes place [Per the Genetic Theory of Recombination].
Mechanism of formation:
- Non-sister chromatids of homologous chromosomes break at specific points.
- The enzyme recombinase catalyzes the exchange of DNA segments between these non-sister chromatids.
- The result is a DNA molecule that contains a combination of alleles not present in either parent, effectively creating a recombinant DNA molecule.
Step 3: Visualization of Crossing Over
Comparison of Genetic States
| Stage | Chromosomal Configuration | Recombination Status |
|---|---|---|
| Zygotene | Synapsis (Pairing) | No |
| Pachytene | Crossing Over | Yes (Recombinant DNA formed) |
| Diplotene | Chiasmata visible | Completed |
Final Solution: Recombinant DNA is formed during the Pachytene stage of Prophase I of meiosis, during the process of crossing over where non-sister chromatids of homologous chromosomes exchange genetic segments mediated by the enzyme recombinase.
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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