NUCLEIC ACIDS
Comparison between DNA and RNA
| DNA | RNA |
|---|---|
| Found mainly in the chromatin of the cell nucleus | Most of RNA (90%) is present in the cell cytoplasm and a little (10%) in the nucleolus. |
| 2. Never present in free state in cytoplasm | 2. May be present in free state. |
| 3. Normally double-stranded and rarely single-stranded. | 3. Normally single-stranded and rarely double-stranded. |
| 4. DNA has both ‘sense' and ‘antisense' strands. | 4. The sequence of an RNA molecule is the same as that of the ‘antisense' strand. |
| 5. Sugar moiety in DNA is 2′-deoxyribose (hence the nomenclature) which contains an H atom at C-2. | 5. Sugar moiety in RNA is ribose (hence the nomenclature) which contains a 2′-hydroxyl group. |
| 6. Sugars in DNA are in the C2′ - endo form. | 6. Sugars in RNA are in the C3′ - endo form. |
| 7. The common nitrogenous bases are adenine, guanine, cytosine and thymine (but not uracil). | 7. The common nitrogenous bases are adenine, guanine, cytosine and uracil (but not thymine) |
| 8. Base pairing is inevitable during which adenine pairs with thymine and guanine with cytosine. | 8. In case pairing takes place, adenine pairs with uracil and guanine with cytosine. |
| 9. The base ratios (A/T and G/C) are necessarily around one. | 9. It need not have complementary base ratios. |
| 10. Base pairing involves the entire length of DNA molecule. | 10. Base pairing takes place in only the helical regions of RNA molecule, which amount to roughly half (50%) of the entire RNA molecule. |
| 11. DNA contains only few unusual bases. | 11. RNA contains comparatively more unusual bases. |
| 12. DNA is of 3 types: | 12. RNA is of 5 types: |
| -----> filamentous (double helical or duplex), | -----> viral RNA, |
| -----> circular or | -----> mRNA and |
| -----> single-stranded. | -----> rRNA |
| -----> tRNA | |
| -----> double-stranded RNA. | |
| 13. It consists of a large number of nucleotides (up to 3-4 million) and has, therefore, high molecular weight. | 13. It consists of fewer nucleotides (up to 12,000) and has, therefore, low molecular weight. |
| 14. DNA is alkali-stable. | 14. RNA is alkali-labile. |
| 15. DNA stains blue with azureph thalate. | 15. RNA stains red with azureph thalate. |
| 16. DNA acts as a template for its synthesis. | 16. RNA does not act as a template for its synthesis. |
| 17. DNA on replication forms DNA and on transcription forms RNA. | 17. Usually RNA does not replicate or transcribe. |
| 18. During replicatin, exonuclease is needed. | 18. During biosynthesis, exonuclease is not needed. |
| 19. DNA undergoes mutation. | 19. RNA does not undergo mutation. |
| 20. DNA is the usual genetic material. | 20. RNA is the genetic material of some viruses only. |
| 21. DNA is stained green with a dye, pyronin. | 21. RNA is stained red with pyronin. |