GRE Subject Biology


  • The test consists of approximately 200 five-choice questions, a number of which are grouped in sets toward the end of the test and are based on descriptions of laboratory and field situations, diagrams or experimental results.
  • The content of the test is organized into three major areas: cellular and molecular biology, organismal biology and ecology and evolution. Approximately equal weight is given to each of these three areas. In addition to the total score, a subscore in each of these subfield areas is reported. Subject area subdivisions indicated by Arabic numerals may not contain equal numbers of questions.

The approximate distribution of questions by content category is shown below.


  • Fundamentals of cellular biology, genetics and molecular biology are addressed.
  • Major topics in cellular structure and function include metabolic pathways and their regulation, membrane dynamics and cell surfaces, organelles, cytoskeleton, and cell cycle.
  • Major areas in genetics and molecular biology include chromatin and chromosomal structure, genomic organization and maintenance, and the regulation of gene expression.
  • The cellular basis of immunity and the mechanisms of antigen-antibody interactions are included. Distinctions between prokaryotic and eukaryotic cells are considered where appropriate.
  • Attention is also given to experimental methodology.
  1. Cellular Structure and Function (16–17%)
    1. Biological compounds
      • Macromolecular structure and bonding
      • Abiotic origin of biological molecules
    2. Enzyme activity, receptor binding and regulation
    3. Major metabolic pathways and regulation
      • Respiration, fermentation and photosynthesis
      • Synthesis and degradation of macromolecules
      • Hormonal control and intracellular messengers
    4. Membrane dynamics and cell surfaces
      • Transport, endocytosis and exocytosis
      • Electrical potentials and transmitter substances
      • Mechanisms of cell recognition, cell junctions and plasmodesmata
      • Cell wall and extracellular matrix
    5. Organelles: structure, function, synthesis and targeting
      • Nucleus, mitochondria and plastids
      • Endoplasmic reticulum and ribosomes
      • Golgi apparatus and secretory vesicles
      • Lysosomes, peroxisomes and vacuoles
    6. Cytoskeleton, motility and shape
      • Actin-based systems
      • Microtubule-based systems
      • Intermediate filaments
      • Bacterial flagella and movement
    7. Cell cycle, growth, division and regulation (including signal transduction)
    8. Methods
      • Microscopy (e.g., electron, light, fluorescence)
      • Separation (e.g., centrifugation, gel filtration, PAGE, fluorescence-activated cell sorting [FACS])
      • Immunological (e.g., Western Blotting, immunohistochemistry, immunofluorescence)
  2. Genetics and Molecular Biology (16–17%)
    1. Genetic foundations
      • Mendelian inheritance
      • Pedigree analysis
      • Prokaryotic genetics (transformation, transduction and conjugation)
      • Genetic mapping
    2. Chromatin and chromosomes
      • Nucleosomes
      • Karyotypes
      • Chromosomal aberrations
      • Polytene chromosomes
    3. Genome sequence organization
      • Introns and exons
      • Single-copy and repetitive DNA
      • Transposable elements
    4. Genome maintenance
      • DNA replication
      • DNA mutation and repair
    5. Gene expression and regulation in prokaryotes and eukaryotes: mechanisms
      • The operon
      • Promoters and enhancers
      • Transcription factors
      • RNA and protein synthesis
      • Processing and modifications of both RNA and protein
    6. Gene expression and regulation: effects
      • Control of normal development
      • Cancer and oncogenes
      • Whole genome expression (e.g., microarrays)
      • Regulation of gene expression by RNAi (e.g., siRNA)
      • Epigenetics
    7. Immunobiology
      • Cellular basis of immunity
      • Antibody diversity and synthesis
      • Antigen-antibody interactions
    8. Bacteriophages, animal viruses and plant viruses
      • Viral genomes, replication, and assembly
      • Virus-host cell interactions
    9. Recombinant DNA methodology
      • Restriction endonucleases
      • Blotting and hybridization
      • Restriction fragment length polymorphisms
      • DNA cloning, sequencing and analysis
      • Polymerase chain reaction


  • The structure, physiology, behavior and development of plants and animals are addressed.
  • Topics covered include nutrient procurement and processing, gas exchange, internal transport, regulation of fluids, control mechanisms and effectors, and reproduction in autotrophic and heterotrophic organisms.
  • Examples of developmental phenomena range from fertilization through differentiation and morphogenesis.
  • Perceptions and responses to environmental stimuli are examined as they pertain to both plants and animals.
  • Major distinguishing characteristics and phylogenetic relationships of selected groups from the various kingdoms are also covered.
  1. Animal Structure, Function and Organization (10%)
    1. Exchange with environment
      • Nutrient, salt and water exchange
      • Gas exchange
      • Energy
    2. Internal transport and exchange
      • Circulatory and digestive systems
    3. Support and movement
      • Support systems (external, internal and hydrostatic)
      • Movement systems (flagellar, ciliary and muscular)
    4. Integration and control mechanisms
      • Nervous and endocrine systems
    5. Behavior (communication, orientation, learning and instinct)
    6. Metabolic rates (temperature, body size and activity)
  2. Animal Reproduction and Development (6%)
    1. Reproductive structures
    2. Meiosis, gametogenesis and fertilization
    3. Early development (e.g., polarity, cleavage and gastrulation)
    4. Developmental processes (e.g., induction, determination, differentiation, morphogenesis and metamorphosis)
    5. External control mechanisms (e.g., photoperiod)
  3. Plant Structure, Function and Organization, with Emphasis on Flowering Plants (7%)
    1. Organs, tissue systems, and tissues
    2. Water transport, including absorption and transpiration
    3. Phloem transport and storage
    4. Mineral nutrition
    5. Plant energetics (e.g., respiration and photosynthesis)
  4. Plant Reproduction, Growth and Development, with Emphasis on Flowering Plants (5%)
    1. Reproductive structures
    2. Meiosis and sporogenesis
    3. Gametogenesis and fertilization
    4. Embryogeny and seed development
    5. Meristems, growth, morphogenesis and differentiation
    6. Control mechanisms (e.g., hormones, photoperiod and tropisms)
  5. Diversity of Life (6%)
    1. Archaea
      • Morphology, physiology and identification
    2. Bacteria (including cyanobacteria)
      • Morphology, physiology, pathology and identification
    3. Protista
      • Protozoa, other heterotrophic Protista (slime molds and Oomycota) and autotrophic Protista
      • Major distinguishing characteristics
      • Phylogenetic relationships
      • Importance (e.g., eutrophication, disease)
    4. Fungi
      • Distinctive features of major phyla (vegetative, asexual and sexual reproduction)
      • Generalized life cycles
      • Importance (e.g., decomposition, biodegradation, antibiotics and pathogenicity)
      • Lichens
    5. Animalia with emphasis on major phyla
      • Major distinguishing characteristics
      • Phylogenetic relationships
    6. Plantae with emphasis on major phyla
      • Alternation of generations
      • Major distinguishing characteristics
      • Phylogenetic relationships


  • This section deals with the interactions of organisms and their environment, emphasizing biological principles at levels above the individual.
  • Ecological and evolutionary topics are given equal weight.
  • Ecological questions range from physiological adaptations to the functioning of ecosystems.
  • Although principles are emphasized, some questions may consider applications to current environmental problems.
  • Questions in evolution range from its genetic foundations through evolutionary processes to their consequences.
  • Evolution is considered at the molecular, individual, population and higher levels.
  • Principles of ecology, genetics and evolution are interrelated in many questions.
  • Some questions may require quantitative skills, including the interpretation of simple mathematical models.
  1. Ecology (16–17%)
    1. Environment/organism interaction
      • Biogeographic patterns
      • Physiological ecology
      • Temporal patterns (e.g., seasonal fluctuations)
    2. Behavioral ecology
      • Habitat selection
      • Mating systems
      • Social systems
      • Resource acquisition
    3. Population Structure and Function
      • Population dynamics/regulation
      • Demography and life history strategies
    4. Communities
      • Direct and indirect interspecific interactions
      • Community structure and diversity
      • Change and succession
    5. Ecosystems
      • Productivity and energy flow
      • Chemical cycling
  2. Evolution (16–17%)
    1. Genetic variability
      • Origins (mutations, linkage, recombination and chromosomal alterations)
      • Levels (e.g., polymorphism and heritability)
      • Spatial patterns (e.g., clines and ecotypes)
      • Hardy-Weinberg equilibrium
    2. Evolutionary processes
      • Gene flow and genetic drift
      • Natural selection and its dynamics
      • Levels of selection (e.g., individual and group)
      • Trade-offs and genetic correlations
      • Natural selection and genome evolution
      • Synonymous vs. nonsynonymous nucleotide ratios
    3. Evolutionary consequences
      • Fitness and adaptation
      • Speciation
      • Systematics and phylogeny
      • Convergence, divergence and extinction
      • Coevolution
    4. History of life
      • Origin of prokaryotic and eukaryotic cells
      • Fossil record
      • Paleontology and paleoecology
      • Lateral transfer of genetic sequences

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