Reproduction key terms

Gamete

A haploid reproductive cell produced by meiosis, carrying one set of chromosomes and capable of fusing with another gamete during fertilisation.

Fusion

The process by which two gametes (sperm and egg) combine to form a diploid zygote, restoring the full chromosome number.

gametes

Reproductive cells that unite during sexual reproduction to form a new organism; in animals, these are sperm and egg cells, while in flowering plants, they are pollen and egg cells.

sperm and egg cells

The male and female gametes in animals, respectively, that are involved in sexual reproduction.

sexual reproduction

A reproductive process involving the fusion of male and female gametes, resulting in offspring with mixed genetic information.

variation

The differences in genetic traits among offspring produced through sexual reproduction, contributing to diversity within a population.

Gamete formation

The process by which cells in the reproductive organs divide by meiosis to produce male and female gametes.

Meiosis

A two‑stage cell division that halves the chromosome number, producing four genetically distinct gametes.

asexual reproduction

A form of reproduction that involves only one parent, does not involve the fusion of gametes, and results in offspring that are genetically identical to the parent.

gamete fusion

The process by which male and female gametes combine during sexual reproduction to form a zygote, leading to genetic mixing.

asexual reproduction

A form of reproduction involving a single parent that produces genetically identical offspring without the fusion of gametes.

clones

In Sexual and asexual reproduction, clones means the specific Unit 4.6 idea used to answer this objective: students must explain that asexual reproduction produces genetically identical offspring called clones and involves only mitosis. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use clones as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

Meiosis

A type of cell division that reduces the chromosome number by half, resulting in the formation of gametes.

Gametes

Reproductive cells (sperm and egg in animals, pollen and egg in plants) that carry half the genetic information of an organism.

fertilisation

The process by which a sperm cell and an egg cell unite to form a zygote, restoring the diploid number of chromosomes.

chromosomes

Thread‑like structures within the nucleus that carry genetic material; in fertilisation the combined set from both gametes restores the full chromosome complement.

meiosis

A type of cell division that reduces the chromosome number by half, resulting in the formation of gametes.

gametes

Reproductive cells (sperm and egg in animals, pollen and egg in plants) that fuse during fertilization to form a new organism.

meiosis

A type of cell division that reduces the chromosome number by half, resulting in the formation of gametes.

genetic information

The hereditary material in a cell, which is copied before meiosis to ensure each gamete receives the correct genetic content.

Meiosis

The two‑stage cell division process that reduces the chromosome number by half, producing four haploid gametes.

Gamete

A haploid reproductive cell (sperm or egg) that contains a single set of chromosomes and is produced by meiosis.

Gamete

A haploid reproductive cell (sperm or egg) that contains half the number of chromosomes of a normal body cell.

Genetic variation

The differences in DNA sequences between individual gametes, ensuring that each gamete carries a unique combination of genes.

fertilisation

The process where male and female gametes fuse to form a zygote, restoring the full number of chromosomes.

mitosis

A type of cell division that results in two genetically identical daughter cells, crucial for growth and development after fertilisation.

meiosis

A type of cell division that reduces the chromosome number by half, producing four genetically diverse gametes.

chromosome behaviour

The specific actions and arrangements of chromosomes during the stages of meiosis, including pairing, crossing over, and segregation.

sexual reproduction

A reproductive process that involves the joining or fusion of male and female gametes, resulting in offspring with mixed genetic information.

variation

Differences in the characteristics of offspring produced through sexual reproduction, which can provide a survival advantage in changing environments.

Variation

The presence of differences in traits among individuals within a population, arising from genetic differences such as allele combinations.

Survival advantage

The increased likelihood of an organism surviving and reproducing in a changing environment due to possessing beneficial traits.

Selective breeding

A human-controlled process of choosing parents with desirable traits to produce offspring that inherit those traits, thereby accelerating natural selection for improved food production.

Artificial selection

The intentional selection of organisms with specific characteristics for breeding, used by humans to enhance crop yields and livestock quality.

asexual reproduction

A form of reproduction involving a single parent that produces genetically identical offspring without the fusion of gametes.

advantages of asexual reproduction

Benefits of asexual reproduction include faster reproduction rates, lower time and energy costs, and the ability to produce many identical offspring in favorable conditions.

sexual reproduction

A reproductive process involving the fusion of male and female gametes, resulting in offspring with mixed genetic information.

asexual reproduction

A reproductive process that involves only one parent, does not require gamete fusion, and produces genetically identical offspring.

asexual reproduction

A form of reproduction involving one parent that produces genetically identical offspring without the fusion of gametes.

sexual reproduction

A reproductive process that involves the fusion of male and female gametes, resulting in offspring with mixed genetic information.

spores

Reproductive structures produced by fungi that can develop into new individuals without fertilisation, enabling asexual reproduction.

sexual reproduction

Fungal reproduction involving the fusion of gametes or specialised cells, producing genetically varied offspring.

runners

A method of asexual reproduction in plants where new plants grow from horizontal stems that extend from the parent plant.

bulb division

A form of asexual reproduction in which a bulb, a storage organ, divides to produce new plants, as seen in daffodils.

sexual reproduction

A reproductive process involving the fusion of male and female gametes, resulting in offspring with mixed genetic information.

asexual reproduction

A reproductive process that involves only one parent, does not require gamete fusion, and produces genetically identical offspring.

reproduction examples

Specific instances of sexual or asexual reproduction methods that are outlined in the curriculum.

organism specificity

The concept that knowledge of reproduction is limited to the organisms explicitly mentioned in the specification.

DNA

The genetic material that carries the instructions for the development, functioning, growth, and reproduction of all known living organisms and many viruses.

Nucleus

The membrane-bound organelle in eukaryotic cells that contains the cell's genetic material (DNA) and controls cellular activities.

DNA

The genetic material in the nucleus of a cell, composed of two complementary strands that coil into a double‑helix structure.

Double helix

The three‑dimensional shape formed when two DNA strands wind around each other, giving DNA its characteristic twisted ladder appearance.

chromosome

A thread‑like structure found in the nucleus of a cell that contains DNA and proteins, and which carries genetic information.

DNA

In DNA and the genome, DNA means the specific Unit 4.6 idea used to answer this objective: students must explain that DNA is contained in structures called chromosomes. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use DNA as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

gene

In DNA and the genome, gene means the specific Unit 4.6 idea used to answer this objective: students must define a gene as a small section of DNA on a chromosome. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use gene as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

chromosome

A chromosome is a structure within the cell nucleus that contains DNA and carries genetic information.

gene

In DNA and the genome, gene means the specific Unit 4.6 idea used to answer this objective: students must explain that each gene codes for a sequence of amino acids to make a specific protein. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use gene as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

amino acids

The building blocks of proteins, which are linked together in a specific sequence as determined by the gene.

genome

In DNA and the genome, genome means the specific Unit 4.6 idea used to answer this objective: students must define the genome as the entire genetic material of an organism. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use genome as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

gene

In DNA and the genome, the term gene has a specific definition boundary role in Unit 4.6. Use gene when students must define the genome as the entire genetic material of an organism. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use gene as a vague inheritance word or as a synonym for a neighbouring term; link it to Reproduction, DNA and the genome, and the exact role it plays in AQA GCSE Biology. Revision cue 1: When asking about DNA, test molecular structure, base sequence, nucleotides, or genetic information storage.

Human genome

The complete set of genetic material in a human cell, comprising all genes and non‑coding DNA, which can be analysed to identify disease‑linked genes, understand inherited disorders and trace human migration patterns.

Genetic variation

Differences in DNA sequence between individuals that can influence the presence of disease‑linked alleles, affect inherited disorder risk and provide evidence for patterns of human migration.

nucleotide

The basic building block of DNA, consisting of a sugar, a phosphate group, and one of four bases (adenine, cytosine, guanine, or thymine).

polymer

A large molecule composed of repeating structural units, in this case, nucleotides that form the DNA strand.

nucleotide

A nucleotide is the basic building block of DNA, consisting of a sugar, a phosphate group, and one of four nitrogenous bases (adenine, cytosine, guanine, or thymine).

double helix

The double helix is the structure of DNA, formed by two strands of nucleotides twisted around each other, with bases pairing specifically (A with T and C with G).

DNA bases

The four nitrogenous bases that make up DNA: adenine (A), cytosine (C), guanine (G) and thymine (T).

Nucleotide

The basic building block of DNA, consisting of a sugar, a phosphate group and one of the four bases (A, C, G, or T).

triplet code

In DNA structure (biology only), triplet code means the specific Unit 4.6 idea used to answer this objective: students must explain that a sequence of three bases codes for a particular amino acid. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use triplet code as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

amino acid

The building blocks of proteins, each coded for by a specific sequence of three bases in DNA.

bases

The building blocks of DNA, consisting of adenine (A), cytosine (C), guanine (G), and thymine (T), which determine the genetic code.

amino acid

The organic compounds that serve as the building blocks of proteins, with their sequence determined by the order of bases in DNA.

sugar

The five‑carbon backbone component of a nucleotide that links to phosphate groups and bases in the DNA strand.

phosphate

The negatively charged group that connects adjacent sugars, forming the sugar‑phosphate backbone of DNA.

DNA double helix

The three‑dimensional shape of DNA, formed by two complementary strands winding around each other.

nucleotide

The basic building block of DNA, consisting of a sugar, a phosphate group and one of four bases (A, C, G, T).

protein synthesis

The process by which cells use ribosomes to assemble amino acids into proteins based on the sequence of nucleotides in mRNA.

ribosome

A cellular structure that facilitates the translation of mRNA into a polypeptide chain during protein synthesis.

DNA structure

The arrangement of nucleotides in a double‑helical polymer, where complementary bases (A with T, C with G) pair to form a stable sequence that determines the order of amino acids in a protein.

Amino acid sequence

The linear order of amino acids encoded by a gene’s DNA sequence, which dictates the protein’s shape and function.

Complementary base pairing

The specific matching of nitrogenous bases in DNA, where cytosine (C) pairs with guanine (G) and thymine (T) pairs with adenine (A), forming the double‑helix structure.

Base pairing rule

The principle that dictates which bases pair together in DNA: C↔G and A↔T, ensuring accurate replication and transcription of genetic information.

mutation

In DNA structure (biology only), mutation means the specific Unit 4.6 idea used to answer this objective: students must explain (HT only) how a mutation may change the protein synthesised by a gene. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use mutation as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

protein synthesis

The process by which cells use genetic information to produce proteins, which are essential for various cellular functions.

Coding DNA

The portion of a gene’s DNA sequence that is transcribed into mRNA and translated into a protein, determining the amino acid sequence of that protein.

Phenotype

The observable characteristics or traits of an organism that result from the interaction of its genotype with the environment.

Non‑coding DNA

Regions of the genome that do not code for proteins but can influence gene expression and thereby affect an organism’s phenotype.

Gene expression regulation

The processes by which variations in non‑coding DNA alter the level, timing or location of gene transcription, ultimately influencing the phenotype.

mRNA

Messenger RNA, the RNA copy of a gene’s coding sequence that carries the genetic message from DNA to the ribosome.

tRNA

Transfer RNA, the adaptor RNA that brings specific amino acids to the ribosome during protein synthesis.

insertions

Insertions are mutations where one or more nucleotide bases are added into the DNA sequence, potentially altering the protein produced.

deletions

Deletions are mutations where one or more nucleotide bases are removed from the DNA sequence, which can lead to changes in the resulting protein.

Gamete

A haploid reproductive cell (sperm or egg) that contains one complete set of chromosomes and fuses with another gamete during fertilisation.

Chromosome

A thread‑like structure made of DNA and protein that carries genes and determines the genetic information passed from parent to offspring.

allele

In Genetic inheritance, allele means the specific Unit 4.6 idea used to answer this objective: students must explain the terms allele, dominant and recessive. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use allele as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

dominant

In Genetic inheritance, the term dominant has a specific definition boundary role in Unit 4.6. Use dominant when students must explain the terms allele, dominant and recessive. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use dominant as a vague inheritance word or as a synonym for a neighbouring term; link it to Reproduction, Genetic inheritance, and the exact role it plays in AQA GCSE Biology. Revision cue 1: When asking about DNA, test molecular structure, base sequence, nucleotides, or genetic information storage.

homozygous

In Genetic inheritance, homozygous means the specific Unit 4.6 idea used to answer this objective: students must explain the terms homozygous and heterozygous. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use homozygous as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

heterozygous

In Genetic inheritance, the term heterozygous has a specific definition boundary role in Unit 4.6. Use heterozygous when students must explain the terms homozygous and heterozygous. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use heterozygous as a vague inheritance word or as a synonym for a neighbouring term; link it to Reproduction, Genetic inheritance, and the exact role it plays in AQA GCSE Biology. Revision cue 1: When asking about DNA, test molecular structure, base sequence, nucleotides, or genetic information storage.

genotype

The genetic constitution of an individual, representing the specific alleles inherited from both parents.

phenotype

The observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

single-gene characteristics

Traits that are determined by the expression of a single gene, such as fur color in mice and red-green color blindness in humans.

allele

Different forms of a gene that can exist at a specific locus on a chromosome, influencing single-gene characteristics.

Allele

In Genetic inheritance, Allele means the specific Unit 4.6 idea used to answer this objective: students must explain that different forms of a gene are called alleles. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use Allele as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

Gene

In Genetic inheritance, the term Gene has a specific definition boundary role in Unit 4.6. Use Gene when students must explain that different forms of a gene are called alleles. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use Gene as a vague inheritance word or as a synonym for a neighbouring term; link it to Reproduction, Genetic inheritance, and the exact role it plays in AQA GCSE Biology. Revision cue 1: When asking about DNA, test molecular structure, base sequence, nucleotides, or genetic information storage.

Genotype

The complete set of alleles present in an individual’s genome that determines the genetic potential for a trait.

Phenotype

The observable physical or biochemical characteristics of an individual resulting from the interaction of its genotype with the environment.

dominant allele

An allele that is expressed in the phenotype when at least one copy is present in the genotype.

genotype

The genetic constitution of an individual, specifically the alleles present for a particular gene.

recessive allele

A form of a gene that is only expressed when an individual has two copies and no dominant allele is present.

dominant allele

A form of a gene that is expressed when at least one copy is present, masking the effect of a recessive allele.

gene

In Genetic inheritance, gene means the specific Unit 4.6 idea used to answer this objective: students must explain that most characteristics result from multiple genes interacting rather than single-gene inheritance. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use gene as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

polygenic

In Genetic inheritance, the term polygenic has a specific definition boundary role in Unit 4.6. Use polygenic when students must explain that most characteristics result from multiple genes interacting rather than single-gene inheritance. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use polygenic as a vague inheritance word or as a synonym for a neighbouring term; link it to Reproduction, Genetic inheritance, and the exact role it plays in AQA GCSE Biology. Revision cue 1: When asking about DNA, test molecular structure, base sequence, nucleotides, or genetic information storage.

Gene

In Genetic inheritance, Gene means the specific Unit 4.6 idea used to answer this objective: students must use probability to predict the results of a single-gene cross. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use Gene as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

Probability

The likelihood of a particular genotype or phenotype occurring in the offspring of a single-gene cross, expressed as a ratio or percentage.

Direct proportion

A relationship in which the ratio of two quantities remains constant, used to predict the relative frequencies of genotypes or phenotypes in a genetic cross.

Simple ratio

A comparison of two or more numbers expressed as a fraction or whole numbers, applied to describe the expected proportions of outcomes in a genetic cross.

Punnett square

A diagram used to predict the outcome of a genetic cross by showing all possible combinations of alleles from the parents.

genetic cross

The mating of two organisms to analyze the inheritance of specific traits based on their genetic makeup.

Punnett square

A diagram used to predict the outcome of a genetic cross by showing the possible combinations of alleles from the parents.

probability

A measure of the likelihood that a particular genetic outcome will occur, often expressed as a fraction or percentage.

Allele

A variant form of a gene that occupies a specific position on a chromosome and can influence a particular trait.

Inherited disorder

A disease or condition that arises when a harmful allele is passed from parent to offspring.

polydactyly

In Inherited disorders, polydactyly means the specific Unit 4.6 idea used to answer this objective: students must describe polydactyly as an inherited disorder caused by a dominant allele. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use polydactyly as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

dominant allele

A gene variant that is expressed in the phenotype even when only one copy is present.

cystic fibrosis

An inherited disorder that affects the cell membranes, caused by a recessive allele.

recessive allele

An allele that is expressed only when two copies are present and no dominant allele is present.

Dominant allele

A form of a gene that is expressed in the phenotype when present in a single copy, masking the effect of a recessive allele.

Recessive allele

A form of a gene that is expressed in the phenotype only when two copies are present and no dominant allele is present.

embryo screening

A medical procedure used to identify genetic disorders in embryos before implantation.

ethical issues

Moral considerations and implications related to the practices and consequences of embryo screening.

Embryo screening

In Inherited disorders, Embryo screening means the specific Unit 4.6 idea used to answer this objective: students must consider that embryo screening and gene therapy may alleviate suffering but raise ethical issues. Keep the term curriculum-specific by applying this boundary: DNA is the molecule; a gene is a functional section of that molecule. Do not use Embryo screening as a vague inheritance word; link it to Reproduction and explain the exact role it plays in AQA GCSE Biology.

Gene therapy

A medical intervention that modifies or replaces defective genes to treat or prevent disease.

chromosome pairs

Ordinary human body cells contain 23 pairs of chromosomes, which include 22 pairs that control characteristics and one pair that determines sex.

human body cells

Cells in the human body that contain genetic material organized into 23 pairs of chromosomes.

chromosome pairs

Pairs of chromosomes that contain genes controlling various characteristics of an organism.

sex determination

The process by which the sex of an organism is established, determined by the presence of specific sex chromosomes.

XX sex chromosomes

The pair of sex chromosomes found in female humans, consisting of two X chromosomes.

female sex determination

The genetic mechanism by which the presence of two X chromosomes (XX) results in the development of female characteristics.

Sex chromosomes

Chromosomes that determine the sex of an individual, with females having two X chromosomes (XX) and males having one X and one Y chromosome (XY).

XY chromosome pair

The combination of one X chromosome from the mother and one Y chromosome from the father that identifies a male individual.

genetic cross

A diagrammatic representation of the possible combinations of alleles from two parents, used to predict the distribution of traits in offspring.

sex inheritance

The pattern by which sex chromosomes (XX or XY) are transmitted from parents to offspring, determining the sex of the individual.

Genetic cross

A diagrammatic representation, such as a Punnett square, that shows the possible combinations of alleles from two parents and predicts the genotypic and phenotypic ratios of their offspring.

Direct proportion

A relationship in which the ratio of two quantities remains constant; in sex‑determination crosses it means that the proportion of male to female offspring is fixed by the parental genotypes.