Acidi nucleici_cromosomi_cariotipo

It seems like you've compiled a comprehensive set of notes on DNA, RNA, chromatin structure, and histone modifications. Here's a structured summary to help organize the key points: ### 1. **DNA Structure** - **Double Helix**: Composed of two strands with complementary base pairing (A-T, C-G). - **Single-Stranded DNA**: Typically forms a single helical structure. - **Palindromic Sequences**: Sequences that read the same forwards and backwards. ### 2. **RNA Structure** - **Types of RNA**: - Messenger RNA (mRNA) - Ribosomal RNA (rRNA) - Transfer RNA (tRNA) - Small Nuclear RNA (snRNA), Small Cajal Body RNA (scRNA), Small Nucleolar RNA (snoRNA), MicroRNA - **Base Pairing**: Uracil replaces Thymine in RNA. ### 3. **Compaction of DNA** - **Heterochromatin vs Euchromatin**: - Heterochromatin: Highly condensed, transcriptionally inactive. - Euchromatin: Less condensed, actively transcribed. - **Nucleosomes**: DNA wraps around histone proteins to form a bead-like structure. - **30nm Fiber**: Nucleosomes stack to form a 30nm fiber. ### 4. **Histone Structure and Modifications** - **Histones**: - H1, H2A, H2B, H3, H4 - Domains: Globular (H2A, H2B, H3, H4) and Tail (NH2- and COOH-terminal). - **Chromatin Modifications**: - Acetylation of Lysine residues. - Methylation of Lysine residues. - **Chromatin Remodeling**: Processes that alter the positioning and spacing of nucleosomes. ### 5. **Compaction Mechanisms** - **Isonucleosomes Interaction**: Hypothesis suggests interactions between isonucleosome tails help form higher-order structures. - **Phosphorylation Kinases and Phosphatases**: Enzymes involved in modifying histone modifications, affecting chromatin structure. ### 6. **Chromatin Remodeling** - **Multiprotein Complexes**: Use ATP hydrolysis to remodel nucleosomes. - **ATP-Dependent Chromatin Remodeling**: Processes that alter the position and spacing of nucleosomes or interactions between histones and DNA. ### 7. **DNA Packaging in Cells** - **Cell Types**: - Prokaryotes: DNA ~10 μm - Eukaryotes (Human): DNA ~1.7 m, organized into 46 chromosomes. - **N