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• Chromatin (intro) — Chromatin is the DNA–protein complex that packages eukaryotic genomes and helps regulate gene access.
• Chromatin structure (intermediate) — Chromatin structure describes how DNA and histones are organized from nucleosomes to higher-order domains.
• Chromatin function (intermediate) — Chromatin functions in packaging the genome, regulating access for transcription, and supporting replication and repair.
• Chromatin organization (intermediate) — Chromatin organization describes spatial and regional patterns of genome packaging in the nucleus.
• Chromatin compaction (intermediate) — Chromatin compaction is the folding of DNA–protein fibers into denser forms, culminating in mitotic chromosomes.
• Chromatin accessibility (intermediate) — Chromatin accessibility describes how easily proteins can contact DNA within packaged chromatin.
• Chromatin remodeling (advanced) — Chromatin remodeling uses specialized complexes to slide, eject, or restructure nucleosomes and change DNA access.
• Chromatin and the cell cycle (intermediate) — Chromatin organization changes across the cell cycle, from accessible interphase forms to condensed mitotic chromosomes.
• DNA (intro) — DNA stores genetic information as a sequence of nucleotide bases in a double helix.
• DNA structure (intro) — DNA structure features a sugar-phosphate backbone and complementary base pairs forming a double helix.
• DNA replication (intermediate) — DNA replication copies the genome by using each strand as a template for a new complementary strand.
• DNA packaging (intro) — DNA packaging describes how long DNA molecules are folded with proteins to fit and function in cells.
• DNA base pairing (intro) — DNA base pairing pairs A with T and G with C, enabling complementary strands and accurate copying.
• Double helix (intro) — The double helix is the twisted-ladder structure of two complementary DNA strands.
• DNA mutation (intermediate) — A DNA mutation is a change in DNA sequence that can alter RNA and protein products or regulatory sites.
• DNA repair (intermediate) — DNA repair pathways detect and correct DNA damage or replication errors to protect genome integrity.
• Gene (intro) — A gene is a DNA segment that contains information for a functional product, typically an RNA or protein.
• Gene expression (intro) — Gene expression uses information in a gene to make a functional RNA or protein product.
• Gene regulation (intermediate) — Gene regulation controls when, where, and how much gene products are made.
• Promoter (intro) — A promoter is a regulatory DNA region where transcription machinery assembles to start transcription.
• Enhancer (intermediate) — An enhancer is a regulatory DNA element that increases transcription of a target gene, often from a distance.
• Transcription factor (intermediate) — Transcription factors are proteins that bind specific DNA sequences to activate or repress transcription.
• Coding DNA (intro) — Coding DNA is sequence that specifies the amino-acid sequence of a protein via codons in mRNA.
• Noncoding DNA (intro) — Noncoding DNA does not specify protein amino-acid sequence but includes many functional regulatory and structural elements.
• Genome (intro) — A genome is the complete genetic material of an organism or cell type under study.
• Genomics (intermediate) — Genomics is the study of genomes using sequencing, comparison, and large-scale functional analysis.
• Histones (intro) — Histones are the core packaging proteins of chromatin that form the nucleosome octamer.
• Histone H1 (intermediate) — Histone H1 is a linker histone that binds linker DNA and helps stabilize higher-order chromatin folding.
• Histone H2A (intermediate) — Histone H2A is a core histone that pairs with H2B in the nucleosome octamer.
• Histone H2B (intermediate) — Histone H2B is a core histone that pairs with H2A in the nucleosome octamer.
• Histone H3 (intermediate) — Histone H3 is a core histone central to the nucleosome and rich in regulatory tail modifications.
• Histone H4 (intermediate) — Histone H4 is a highly conserved core histone that forms a tetramer with H3 in the nucleosome.
• Histone modification (intermediate) — Histone modifications are chemical marks on histone proteins that help regulate chromatin behavior.
• Histone acetylation (intermediate) — Histone acetylation adds acetyl groups to lysines and often correlates with more accessible, active chromatin.
• Histone methylation (intermediate) — Histone methylation adds methyl groups to residues such as lysine; outcomes depend on site and context.
• Nucleosome (intro) — The nucleosome is the basic repeating unit of chromatin: DNA wrapped around a histone octamer.
• Nucleosome structure (intermediate) — Nucleosome structure details the histone octamer, wrapped DNA, and protruding histone tails.
• Nucleosome positioning (advanced) — Nucleosome positioning refers to where nucleosomes sit along DNA and how that placement affects access to sequences.
• Linker DNA (intro) — Linker DNA is the DNA segment connecting adjacent nucleosomes in a chromatin array.
• Euchromatin (intermediate) — Euchromatin is generally less compact, more accessible chromatin often enriched for active genes.

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