RNA
RNA (Ribonucleic Acid)
1. Introduction
- RNA (Ribonucleic Acid) is a nucleic acid involved in coding, decoding, regulation, and expression of genes.
- It is essential for translating genetic information from DNA into proteins.
- Discovered in 1868 by Friedrich Miescher, similar to DNA but with distinct features.
2. Chemical Composition
- Made up of monomers called nucleotides.
- Each nucleotide consists of:
- A ribose sugar (a five-carbon sugar)
- A phosphate group
- A nitrogenous base (Adenine, Uracil, Cytosine, Guanine)
3. Types of RNA
- Messenger RNA (mRNA): Carries genetic information from DNA to the ribosomes for protein synthesis.
- Transfer RNA (tRNA): Brings amino acids to ribosomes during translation.
- Ribosomal RNA (rRNA): Forms the core of ribosomes and catalyzes protein synthesis.
- Other types: Small nuclear RNA (snRNA), microRNA (miRNA), and long non-coding RNA (lncRNA) involved in regulation and processing.
4. Structure of RNA
- Usually single-stranded.
- Composed of a chain of nucleotides.
- The sugar in RNA is ribose, which has an extra hydroxyl group (-OH) at the 2' carbon compared to DNA.
- Contains the nitrogenous base Uracil (U) instead of Thymine (T).
5. Nitrogenous Bases in RNA
- Adenine (A)
- Uracil (U)
- Cytosine (C)
- Guanine (G)
6. Functions of RNA
- Protein synthesis: mRNA, tRNA, and rRNA work together during translation.
- Gene regulation: microRNA and other non-coding RNAs regulate gene expression.
- Catalytic roles: Some RNA molecules (ribozymes) have enzymatic activity.
- Viral genomes: Many viruses use RNA as their genetic material.
7. RNA Synthesis (Transcription)
- DNA is transcribed into RNA by RNA polymerase.
- Occurs in the nucleus (in eukaryotic cells).
- The process involves:
- Initiation at promoter regions.
- Elongation of the RNA strand by addition of complementary ribonucleotides.
- Termination when the RNA transcript is complete.
8. RNA Processing (in Eukaryotes)
- Pre-mRNA undergoes modifications:
- Capping: Addition of a 5' cap.
- Polyadenylation: Addition of a poly-A tail at the 3' end.
- Splicing: Removal of introns and joining of exons.
9. Role in Protein Synthesis
- mRNA carries genetic information from DNA.
- tRNA transports amino acids to the ribosome.
- rRNA forms part of the ribosome's structure and catalyzes peptide bond tion
11. Viral RNA
- Many viruses (e.g., influenza, HIV) have RNA genomes.
- Can be single-stranded or double-stranded.
- Replicated and transcribed by viral enzymes.
12. RNA Technologies
- Reverse transcription: RNA can be reverse-transcribed into DNA (used in HIV research).
- RNA interference (RNAi): A process to silence gene expression.
- RNA sequencing: Determines the sequence of RNA molecules.
13. Importance of RNA
- Central in gene expression.
- Used in biotechnology, medicine, and research.
- Target for antiviral drugs and gene therapy.