Biology

A codon is a three-nucleotide sequence that specifies an amino acid or a termination signal during protein synthesis.

Collagen is the most abundant structural protein in animals, forming triple helices that give tissues tensile strength.

The complement system is a regulated network of immune proteins that marks targets for removal, promotes inflammation, and damages susceptible microbial membranes.

A photosynthetic adaptation that separates initial carbon capture at night from daytime carbon assimilation, often reducing water loss.

CRISPR is a microbial genetic defense system whose RNA-guided machinery has been adapted for genome editing, gene regulation, and molecular detection.

Cryo-electron microscopy images rapidly frozen specimens with electron beams to reveal molecular structures and cellular organization in three dimensions.

Cyanobacteria are oxygen-producing photosynthetic bacteria that shape aquatic ecosystems, nutrient cycles, and the evolutionary history of life.

The study of chromosome structure, number, and behavior and their relationships to inheritance, variation, and disease.

A cytokine is a signaling protein that coordinates immune responses and regulates cell activation, growth, differentiation, and survival.

Cytokinesis is the physical division of a cell’s cytoplasm into daughter cells, coordinated with chromosome segregation through mechanisms that differ among organisms.

The cytoskeleton is a dynamic network of protein filaments that organizes cells, provides mechanical support, and enables movement, intracellular transport, and division.

A dendritic cell is an immune cell that presents antigens to T cells, linking pathogen detection with adaptive immunity and contributing to immune tolerance.

Extinct Asian archaic humans closely related to Neanderthals, identified through molecular evidence and ancestral to part of the modern human genome.

DNA is the hereditary nucleic acid whose sequence stores biological information and whose replication, expression, and modification underpin cellular life.

DNA ligases are enzymes that seal breaks in DNA strands, supporting replication, repair, and laboratory DNA assembly.

DNA methylation is a chemical modification of DNA bases that influences genome regulation, cellular identity, and protection against foreign DNA.

DNA mismatch repair corrects replication-associated base-pairing errors and small insertion–deletion loops, preserving genome stability.

DNA polymerases are enzymes that synthesize DNA, supporting genome replication, DNA repair, and laboratory methods such as amplification and sequencing.

DNA repair comprises cellular mechanisms that correct DNA damage and replication errors, helping preserve genetic information.

DNA replication is the semiconservative process by which cells copy their DNA before division, using complementary templates and coordinated enzymes.

DNA sequencing determines the order of nucleotide bases in DNA, enabling analysis of genes, genomes, biological variation, and disease-associated changes.

Effective population size is the size of an idealized population that would experience the same genetic drift, inbreeding, or ancestral processes as a real population.

Efferocytosis is the recognition, engulfment, and degradation of apoptotic cells by phagocytes, supporting tissue maintenance and the resolution of inflammation.

An electrochemical gradient combines chemical and electrical potential differences, determining the energetic direction of ion movement and powering cellular processes.

A membrane-associated system of electron carriers that couples electron transfer to ion gradients, supporting ATP production in respiration and photosynthesis.

The endoplasmic reticulum is a continuous membrane network in eukaryotic cells that produces and processes proteins and lipids, stores calcium, and coordinates intracellular transport.

The endosymbiotic theory explains the bacterial origins of mitochondria and plastids through long-term integration within ancestral host cells.

An enhancer is a DNA regulatory element that increases transcription of a target gene, often in a cell-type-specific or signal-dependent manner.

An enzyme is a biological catalyst that accelerates specific chemical reactions without being consumed in the overall reaction.

Epigenetics studies persistent changes in gene activity that occur without alterations to the DNA sequence, including mechanisms that maintain cellular identity and transmit regulatory states.

An epitope is the specific region of an antigen recognized by an antibody or antigen receptor, defining the molecular specificity of an immune interaction.

An erythrocyte is a red blood cell specialized for transporting oxygen and participating in carbon dioxide transport between respiratory organs and tissues.

Escherichia coli is a Gram-negative bacterium that lives in the mammalian gut and is a central model organism in molecular biology.

A eukaryote is an organism whose cells characteristically contain a membrane-bound nucleus and specialized internal compartments.

Evolution is the change in heritable traits of populations over generations. It explains how all life on Earth descends from a common ancestor and has become diverse.

An exon is a segment of a gene retained in a mature RNA transcript, whether or not it encodes protein.

Extinction is the disappearance of all members of a species or other biological group, ending its existence as a living lineage.

Ferritin is an iron-storage protein that supports cellular iron balance and serves as a blood biomarker of iron stores and inflammation.

A modified nucleotide structure at the 5′ end of most eukaryotic messenger RNAs that supports RNA stability, processing, and translation.

Flow cytometry measures individual cells or particles in a flowing suspension, using light scattering and fluorescence to characterize populations and, in some instruments, separate them.

FOXP3 is a transcription factor essential for regulatory T-cell function and immune tolerance; pathogenic variants in its gene cause IPEX syndrome.

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter of the mature mammalian brain, with roles that extend into peripheral tissues, plants, and microbes.

Gel electrophoresis separates biological molecules in a porous gel using an electric field, enabling analysis of their size, charge, and composition.

A gene is a unit of hereditary information whose sequence encodes a functional RNA or contributes to the production of a protein.

Gene expression is the regulated process through which genetic information produces functional RNA or protein products.

Gene flow is the transfer of genetic material between populations, influencing genetic diversity, adaptation, and evolutionary divergence.

The genetic code is the set of rules by which nucleotide triplets specify amino acids or termination signals during protein synthesis.

Genetic diversity is the variety of inherited genetic differences within and among populations, providing the variation on which evolution acts.

Genetic drift is random change in allele frequencies caused by chance sampling in finite populations, often leading to loss or fixation of variants.

Genetic linkage is the tendency of DNA sequences on the same chromosome to be inherited together, forming the basis of linkage mapping.

Genetics is the study of heredity and biological variation, examining how genetic information is transmitted, expressed, and changed.

A genome is the complete genetic material of an organism or virus, encompassing genes, regulatory sequences, and other coding and noncoding regions.

Genome editing comprises technologies that make targeted changes to DNA sequences for biological research, agriculture, biotechnology, and medicine.

The genetic constitution of an organism or cell, often specified as the alleles present at one or more genomic locations.

A germinal center is a specialized lymphoid structure where activated B cells diversify their antibodies, undergo selection, and generate cells supporting lasting immunity.

Glia are diverse non-neuronal cells that maintain the nervous system, form myelin, regulate neural environments, and participate in immune defense and repair.

Glycogen is a highly branched glucose polymer that stores readily mobilizable carbohydrate, supporting blood glucose regulation and the energy needs of individual tissues.

Glycolysis is a metabolic pathway that converts glucose into pyruvate, generating ATP and NADH without directly requiring oxygen.

Gregor Mendel was an Augustinian friar whose pea-plant experiments established fundamental principles of inheritance and helped found modern genetics.

Hebbian theory explains how coordinated neuronal activity can strengthen connections, providing a foundation for models of learning, memory, and neural computation.