Definitions and Concepts for AQA Biology GCSE - Topic 6: Inheritance, Variation and Evolution

Sep 5, 2026

Study-focused biology glossary covering key AQA Biology GCSE concepts for Topic 6: Inheritance, Variation and Evolution. Provides concise definitions of genetic and evolutionary terms such as allele dominance and recessiveness, genotype and phenotype, DNA, chromosomes, meiosis and mitosis, and classification of organisms. Includes higher-tier and separate-science marked definitions including embryo screening, gene coding and non-coding DNA, mutation, natural selection, evolutionary trees, speciation, extinction, and selective breeding, supporting revision and recall.

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Topic 6: Inheritance, Variation and Evolution

Definitions of genetics and reproduction

Definitions of evolution and classification

Definitions and Concepts for AQA Biology GCSE Topic 6: Inheritance, Variation and Evolution Definitions in bold are for higher tier only Definitions marked by‘*’are for separate sciences only *Adult cell cloning: A type of cloning that forms an embryo from an adult body cell. Allele: A version of a gene. Amino acids: Small molecules from which proteins are assembled. Archaea: Primitive bacteria existing in extreme environments. Asexual reproduction: A form of reproduction involving a single parent. Creates genetically identical offspring. Binomial system: The universal system of naming organisms using their genus and species. Charles Darwin: The scientist who developed the theory of evolution by natural selection. Chromosome: A long, coiled molecule of DNA that carries genetic information in the form of genes. Classification: The organisation of organisms into groups based on their characteristics and structure. *Coding DNA: A sequence of DNA that codes for the production of a protein. *Complementary: Describes how the chemical bases in DNA pair up with each other. A pairs with T and C pairs with G. *Cuttings: The simplest method of cloning plants. A branch is cut from a parent plant andreplanted in compost after removing the lower leaves. Cystic fibrosis: A cellular membrane disorder resulting from the presence of a recessive allele. DNA: A double-stranded polymer wound to form a double helix. Carries the genetic code. Dominant: Describes an allele that is always expressed. Represented by a capital letter. Embryo screening: A procedure used to determine the presence of faulty genes in an embryo produced by IVF. A few embryonic cells are removed and screened for defective alleles. * Embryo transplants: The simplest method of animal cloning. Cells are removed from a developing embryo, split apart and grown in culture, before being transplanted into host mothers. Evolution: The gradual change in the inherited traits within a population over time. Occurs due to natural selection. Evolutionary tree: A diagram which illustrates the evolutionary relationships between organisms. Extinction: The death of all members of a species. Family tree: A chart used to show the inheritance of a condition in a family. Fertilisation: The fusion of the nucleus of male and female gametes. Restores the full chromosome number. Fossil: The remains of dead organisms found in rocks which are millions of years old. Gametes: Sex cells (sperm and egg cells) with half the usual number of chromosomes. Gene: A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein. Genetic engineering: The modification of the genome of an organism by the insertion of a desired gene from another organism, enabling the formation of organisms with beneficial characteristics. Genome: The complete genetic material of an organism. Genotype: An organism’s genetic composition. Describes all alleles. GM crops: Crops that have had their genomes modified by the insertion of a desired gene from another organism. Heterozygous: When someone has two different alleles of a gene e.g. Ff. Homozygous: When someone has two identical alleles of a gene e.g. ff. Inbreeding: The formation of offspring from the breeding of closely related individuals. Linnaean system: The classification of organisms into kingdom, phylum, class, order, family, genus and species, as developed by Carl Linnaeus. Meiosis: A form of cell division that produces gametes, non-identical cells with half the usual number of chromosomes. Mitosis: A form of cell division that produces two genetically identical daughter cells (with a full set of chromosomes) from one parent cell. MRSA: A type of bacteria that is resistant to the antibiotic, methicillin. Mutation: A random change in DNA which may result in genetic variants. Natural selection: The process by which the frequency of advantageous traits passe

FAQs

What is the difference between allele, genotype, and phenotype in this glossary?

An allele is a version of a gene. Genotype describes an organism’s genetic composition (all alleles), while phenotype refers to observable characteristics arising from interactions between genotype and environment.

How do meiosis and mitosis differ according to the definitions provided?

Meiosis produces gametes and generates non-identical cells with half the usual chromosome number. Mitosis produces two genetically identical daughter cells with a full set of chromosomes.

What are natural selection and evolution in Topic 6?

Natural selection is the process in which advantageous traits increase in frequency over time within a population. Evolution is the gradual change in inherited traits within a population over time, occurring due to natural selection.

Sep 5, 2026

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