Molecular evolution

Molecular evolution is the change in DNA, RNA, and protein sequences across generations. Comparing these sequences reveals genetic divergence and the history of life.

Mutation: A heritable change in genetic material, arising through DNA replication errors or other molecular processes. Mutations introduce new sequence variants for evolutionary forces to act on.
DNA: A molecule that stores hereditary information in sequences of four nucleotide bases. DNA sequences provide the most widely analyzed record of molecular change.
Molecular phylogenetics: The reconstruction of evolutionary relationships using molecular sequence data. It turns sequence comparisons into hypotheses about lineage relationships.
Neutral theory of molecular evolution: The theory that most molecular substitutions are selectively neutral and become fixed mainly through genetic drift. It explains many molecular changes without requiring adaptive explanations.
Emile Zuckerkandl: A biochemist who helped establish comparative protein sequences as evidence for evolutionary relationships. His work with Linus Pauling helped frame molecular evolution as a research program.
Natural selection: Differential survival and reproduction that cause heritable traits to become more or less common in a population. Selection changes sequence frequencies when variants affect reproductive success.
RNA: A nucleic acid that functions in gene expression, regulation, catalysis, and hereditary systems. RNA genomes and transcripts also accumulate evolutionary sequence changes.
Phylogenetic tree: A branching diagram representing hypothesized evolutionary relationships among organisms or genes. Trees summarize the divergences inferred from molecular sequences.
Nearly neutral theory: An evolutionary theory in which weakly selected mutations can behave nearly neutrally, depending on population size. It qualifies strict neutrality by linking weak selection to demographic context.
Linus Pauling: An American chemist whose work included pioneering comparisons of protein sequences and molecular disease. His hemoglobin research showed how molecular differences could illuminate evolution.

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