DNA vs RNA: Comprehensive Comparison
| Feature | DNA | RNA |
|---|---|---|
| Full name | Deoxyribonucleic acid | Ribonucleic acid |
| Sugar | 2'-Deoxyribose | Ribose |
| Bases | A, T, G, C | A, U, G, C |
| Base T is replaced by | — | Uracil (U) |
| Strands | Double-stranded (usually) | Single-stranded (usually) |
| Helix type | B-form (physiological) | A-form (dsRNA) |
| Location | Nucleus (mainly), mitochondria | Nucleus + cytoplasm |
| Length | Very long (millions of bp) | Much shorter |
| Stability | More stable (no 2'-OH) | Less stable (2'-OH) |
| Function | Genetic information storage | Protein synthesis (mRNA, tRNA, rRNA) |
| Replication | Semi-conservative, by DNA pol | Transcribed from DNA by RNA pol |
Three RNA Types (NEET essential):
-
mRNA (messenger RNA):
- Carries genetic code from nucleus to ribosome
- Contains codons (triplet sequences specifying amino acids)
- Eukaryote modifications: 5' cap (7-methylguanosine) + 3' poly-A tail + splicing
-
tRNA (transfer RNA):
- Cloverleaf secondary structure (four loops)
- Anticodon loop: complementary + antiparallel to mRNA codon
- 3'-CCA end: attachment site for specific amino acid
- L-shaped in 3D (tertiary structure)
-
rRNA (ribosomal RNA):
- Most abundant RNA type (~80% of total cellular RNA)
- Structural + catalytic component of ribosomes
- Peptidyl transferase activity is rRNA-based (ribozyme)
- Prokaryote ribosome: 70S (50S + 30S); Eukaryote: 80S (60S + 40S)