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Q12(b):
Discuss with your teacher and find out how to distinguish between (b) RNA and DNA
Solution :
Step 1: Chemical Composition and Structural Basis
The fundamental distinction between Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) lies in the composition of their pentose sugar and nitrogenous bases. [Per the central dogma of molecular biology and nucleotide chemistry]:
- DNA: Comprises a 2'-deoxyribose sugar, where the hydroxyl group (-OH) is absent at the 2' position. It utilizes the pyrimidine base Thymine ($T$).
- RNA: Comprises a ribose sugar, possessing a hydroxyl group (-OH) at the 2' position. It replaces Thymine with the pyrimidine base Uracil ($U$).
Step 2: Comparative Analysis of Structural Conformation
| Characteristic | DNA | RNA |
|---|---|---|
| Sugar | 2'-Deoxyribose | Ribose |
| Pyrimidine Bases | Cytosine, Thymine | Cytosine, Uracil |
| Strandedness | Typically double-stranded (Double Helix) | Typically single-stranded |
| Stability | Highly stable (due to deoxyribose and $B$-form geometry) | Unstable (the 2'-OH group promotes alkaline hydrolysis) |
Step 3: Visual Representation of Nucleotide Differences
Step 4: Functional and Evolutionary Implications
The structural disparity described in Step 1 governs the biological utility of the molecules:
- Information Storage: DNA serves as the long-term genetic repository. The absence of the 2'-OH group renders DNA chemically inert and resistant to nucleophilic attack, facilitating stable inheritance [Per the Principle of Chemical Stability].
- Information Expression: RNA acts as an intermediary (mRNA), adapter (tRNA), or catalytic molecule (rRNA). The 2'-OH group facilitates the dynamic structural folding and reactivity necessary for protein synthesis and enzymatic activity (ribozymes).
Step 5: Diagnostic Distinctions
To distinguish these molecules in a laboratory setting:
- Alkaline Hydrolysis: RNA is rapidly degraded in an alkaline environment due to the reactive 2'-hydroxyl group, whereas DNA remains intact.
- Spectral Analysis: Both absorb UV light at $260 \, nm$, but their specific denaturation kinetics ($T_m$ values) differ significantly depending on the buffer and strand complementarity.
Final Solution: DNA and RNA are distinguished by the presence of a 2'-deoxyribose versus ribose sugar, the substitution of Thymine for Uracil in RNA, and a higher relative chemical stability in DNA due to the absence of the 2'-OH group, which makes DNA the primary stable genetic archive and RNA a versatile, transient functional molecule.
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(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(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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