Glossary

Achondroplasia An inherited disorder affecting bone development that results in short-limb dwarfism.

Acquired Immunodeficiency Syndrome (AIDS) The final stage of HIV (human immunodeficiency virus) infection when the immune system has been diminished to the point that the body can no longer fight life-threatening infections.

Acrylamide gel A white, odourless gel used in gel electrophoresis, a method used to separate out molecules such as DNA, based on their size and charge.

Acute A term used to describe the time scale of a disease, acute refers to an illness that is of short duration, develops quickly and requires urgent care.

Adaptor A short, chemically-synthesised, double-stranded DNA molecule which is used to link together two other DNA molecules.

Adenine One of the four nucleotide bases that make up DNA, pairs with thymine (or uracil in RNA).

Adverse drug reaction (ADR) A harmful side effect associated with the use of a medication that has been taken as instructed.

Agarose gel A complex sugar material, generally extracted from seaweed. It is frequently used in molecular biology for the separation of DNA by size using electrophoresis.

Allele Different form of the same gene. In humans, alleles of particular genes come in pairs, and our characteristics are determined by the combination of alleles we have.

Alzheimer’s disease A degenerative disease that slowly and progressively destroys the brain. It is the single most common cause of dementia.

Amino acid The building blocks of proteins, there are 20 different amino acids.

Amoeba A microscopic, single-celled organism that has the ability to alter its shape. Amoebae live in fresh and salt water, in wet soil and in animals.

Amphibian A cold-blooded vertebrate animal that characteristically hatches as aquatic larva with gills before becoming a terrestrial lung-breathing adult. Include frogs, toads, newts and salamanders.

Anaemia A decline in red blood cells or haemoglobin in the blood resulting in a decreased amount of oxygen being carried around the body. It results in tiredness, shortness of breath and pale skin.

Anaemia Condition caused by a lack of red blood cells or lack of haemoglobin in the blood. It results in tiredness, pale skin and shortness of breath.

Antibiotic A type of medicine used to treat or prevent infections caused by bacteria.

Antibiotic resistance When disease-causing bacteria develop the ability to survive exposure to antibiotics that were designed to kill them.

Antibody A protein secreted into the blood or lymph that binds to invading pathogens such as a bacteria, viruses and parasites. This then alerts the immune system to attack and destroy the pathogen.

Apoptosis Also known as programmed or controlled cell death, apoptosis is when a cell commits suicide. It has an important role in human development and disease, for example, apoptosis helps separate our fingers into 10 separate digits.

Arthritis A common condition causing pain and inflammation in the joints.

Assisted reproductive technology A method used to achieve pregnancy by artificial or partially artificial means. For example, in vitro fertilisation (IVF).

Autism A developmental disability that affects how a person communicates with, and relates to, other people. It is often diagnosed in early childhood and is characterised by repetitive behaviour, such as stacking or lining up objects.

Autoimmune disease A condition that occurs when the immune system mistakenly attacks and destroys its own tissue.

Automation Making processes that were once done by hand, into automatic processes using machinery.

Autopsy The surgical examination of a dead body to find out the exact cause of death. Also known as a post-mortem examination.

Autoradiogram An image on a piece of X-ray film that is produced as a consequence of exposure to a radioactive substance. For example, the banding pattern from an electrophoresis gel containing fragments of radioactively labelled DNA.

Autosome A chromosome that is not a sex chromosome, for example chromosomes one to 22.

B-cell Also known as B-lymphocytes, they are a type of cell found in the immune system that produce antibodies to help tackle invading pathogens.

BAC library A collection of DNA fragments stored and cultivated in a population of bacteria, such as E. coli.

Bacteria A type of single celled organism varying in shape from spherical, to spiral to rod-shaped. They are only visible under a microscope and do not have a cell wall, nucleus or organelles. Given the correct conditions bacteria can replicate very quickly and some are harmful and can cause disease.

Bacterial artificial chromosome (BAC) A length of DNA with sequences that allow it to be maintained and reproduced in bacteria. DNA libraries for genome sequencing can be made using BACs: the DNA of interest is inserted into the BAC, and the package is taken up by bacteria. As the bacteria grow and divide, the BAC and the DNA of interest is also copied. BACs were the cornerstone of sequencing the human genome; at the time, they could hold 100,000 - 200,000 base pairs of DNA (100-200 kb); now they can hold double or triple that amount.

Base pair Two bases on opposite strands of a DNA molecule that are held together by weak chemical bonds. In DNA's double helical structure, a base pair forms one 'rung' of the DNA 'ladder'. The rules of base pairing are that A always binds to T and C always binds to G. The bp is also the measurement unit of DNA; the human genome contains more than 3,000,000,000 bp.

Bases The basic unit of our genetic instructions: DNA instructions are encoded in the sequence of its chemical 'letters' or bases. There are four bases: adenine (A), cytosine (C), guanine (G) and thymine (T). Another base, uracil (U) replaces T in RNA.

Biochemical Relating to the chemical processes that occur within living organisms.

Biodiversity The variety of different kinds of life, in the world or in a particular habitat.

Bioinformatics The science of using computer technology to gather, store, analyse and merge biological data. Expertise in bioinformatics is key to handling the enormous amounts of data produced by the Human Genome Project and other sequencing projects, and serving it out to the researchers who use the data. Advances in computer research are as important as the biology for such large scale projects.

Biotechnology The use of living organisms and biological processes to make commercially useful products.

Blood smear A diagnostic test where a thin layer of blood is smeared on a glass slide. This is then examined under a microscope for any abnormalities in platelets, red blood cells and white blood cells.

Body mass index (BMI) A measure of body fat based on your height and weight.

Bone marrow The spongy tissue found in the hollow centre of bones. It contains stem cells which can develop into a variety of cell types, including red blood cells, white blood cells and platelets.

Cancer A common genetic disease caused by mutations in our DNA that lead to uncontrolled cell proliferation and the formation of a tumour.

Capillary A very thin acrylic fibre used in capillary DNA sequencing. DNA is able to pass through the middle of the fibre with small fragments passing through easier than larger fragments.

Carrier An individual who has inherited a genetic trait or mutation but does not display that trait or show symptoms of the disease. This genetic characteristic may be passed on to their offspring.

Cell The basic structural, functional, biological unit of all living organisms. Cells provide structure for the body, take in nutrients from food and carry out the important day-to-day functions for life.

Cell division When one cell splits into two daughter cells, each containing the same genetic material.

Central dogma The process by which the instructions in DNA are converted into a functional product, usually a protein. This involves the DNA instructions being converted to an RNA “message” which is then “translated” to produce a protein, a string of amino acids.

Centromere The region of DNA at the centre of a chromosome which joins the two sister chromatids together.

Chelation Therapy A medical procedure that removes heavy metals, such as mercury, from the blood. A chemical is injected into the patient which then binds to the heavy metal so that it is excreted in the urine.

Chemotherapy A type of cancer treatment that uses chemicals to target and kill rapidly dividing cells in the body. It can lead to side effects such as hair loss.

Chloride An ion formed when a chlorine molecule gains an electron (negatively charged particle) or when hydrogen chloride is dissolved in water.

Chromosome A threadlike structure in our cells, made of a long DNA molecule, wrapped around a protein scaffold. Humans have 23 pairs of chromosomes. Other organisms also have chromosomes, most bacterial chromosomes are loops or circles of DNA.

Chronic A term used to describe the time scale of a disease, chronic refers to an illness that persists for a long time or is constantly reoccurring.

Clinical trials Research investigations that specifically involve human volunteers. Set up to establish the safety and effectiveness of new treatments, such as drugs and vaccines.

Clone An exact copy of something. This can refer to whole organisms or cells but also molecules such as DNA. In sequencing work, small pieces of DNA are stitched into carrier molecules (vectors) that can be copied many times in bacteria or cells. Each copy is called a clone.

Codominance When the alleles of a gene are expressed equally and neither is dominant or recessive.

Codon Sequence of three nucleotide bases which, together, code for an amino acid during the making of a protein.

Colonoscopy This involves a doctor inserting a small camera into a patient via the patient’s bottom to view their colon and identify any abnormalities, for example, cancer.

Complementary The preferential binding of bases A to T (or U) and C to G in DNA or RNA. For example, if there is a GTC on the DNA strand, the complementary RNA or DNA sequence will be CAG. This complementarity maintains the double helical structure of DNA.

Complex disease Common diseases are caused by a combination of genetic, environmental and lifestyle factors. These may run in families and include diseases like diabetes, heart disease, and obesity.

Compound A substance formed when two or more chemical elements are chemically bonded together.

Copy number variation (CNV) Differences in the number of copies of a particular DNA segment between two or more genomes. Variations in copy number have been found within individuals, between individuals and between humans and other mammals. CNVs can result from simple duplications of DNA segments or may involve complex gains or losses of similar DNA sequences at many sites in the genome.

Cystic fibrosis A relatively common genetic condition in which the lungs and digestive system become clogged with thick, sticky mucus. It is due to a specific mutation in a single gene that encodes for the cystic fibrosis transmembrane conductance regulator (CFTR) protein.

Cytosine One of the four nucleotide bases that make up DNA. Pairs with guanine.

Daughter cell A new cell produced when a single cell divides into two.

De novo sequencing When the whole genome of an organism is sequenced and assembled for the first time, without the availability of a reference genome.

De novo sequencing De novo sequencing is when the genome of an organism is sequenced for the first time.

Dementia Term used to describe a general decline in all areas of mental ability. It is caused by brain diseases such as Alzheimer’s disease, or by injury.

Developmental biology The study of the processes involved in controlling the development of an organism from an early embryo to an adult.

Diabetes An incurable condition where the body cannot control its blood sugar levels due to problems with the hormone, insulin. There are two forms of diabetes, type 1 and type 2.

Diploid Term given to a cell with two sets of chromosomes, for example, most of our cells, apart from the sex cells (sperm and egg) and red blood cells.

Direct-to-consumer testing A genetic test that can be bought directly online. It allows consumers to access the information in their genomes without the involvement of a health professional.

DNA A long molecule that contains our unique genetic code. It holds the instructions for making all the proteins in our bodies.

DNA ligase An enzyme that joins together two strands of DNA.

DNA polymerase An enzyme involved in making new DNA molecules from the four nucleotide bases, using the existing DNA as a template.

DNA repair The process by which a cell recognises and corrects damage to its DNA.

DNA replication The process by which a cell makes an identical copy of its genome before it divides.

DNA sequence The order of the bases in a length of DNA.

DNA sequencing The process of determining the order of bases in a length of DNA.

Domain

Highest taxonomic rank of organisms in the three-domain system

Dominant The stronger version of a pair of alleles. Dominant alleles show their effect even if there is only one copy in the genome, for example the allele for brown eyes.

Dopamine A chemical in the body that controls movement, emotional response and our ability to experience pleasure and pain.

Dormant When an organism has its normal functions suspended or slowed down for a period of time, as if in a deep sleep.

Double helix The structure formed by double-stranded molecules of DNA. The double helix structure of DNA was discovered by James Watson and Francis Crick in 1953.

Down's syndrome Also known as Down syndrome or trisomy 21, it is a genetic disorder caused by the presence of all or part of an extra copy of chromosome 21. Often Down's syndrome is associated with delays in, or impairment of, learning and physical development as well as a distinctive facial appearance.

Drug A substance that has a physiological or biochemical effect on our bodies. These effects are generally intended to be beneficial but can cause harm in some people.

Drug resistance The ability of a pathogen to evade the effects of a drug designed to kill or inhibit them.

Ecology Branch of biology dealing with the relationships of organisms with each other and with their environments.

Egg A female reproductive cell. Also called an ovum. Combines with male reproductive cell (sperm) during fertilisation.

Electrode A conductor through which an electric current enters or leaves an object.

Electrophoresis Process by which fragments of DNA are separated according to size under the influence of an electric field applied to a gel or fluid.

Embryo An unborn or unhatched offspring in the process of development.

Embryology Branch of biology focusing on the study of embryos and their development.

Embryonic stem cells Stem cells derived from an early embryo. They have the ability to become any cell type in the body.

Endemic A disease or condition that is common in a particular group of people or location.

Endocarditis A type of heart infection where the inner lining of the heart, called the endocardium, becomes swollen. It usually occurs when bacteria attach to damaged areas of the heart.

Endoscope A medical instrument with a light attached that is used to look inside the body.

Endoscopy A test used to examine the upper part of the gut. A thin, flexible telescope is passed through the mouth, into the oesophagus and down towards the stomach and small intestine.

Enzyme Biological molecules, usually proteins that are responsible for thousands of metabolic processes essential to life.

Epidemic The rapid spread of an infectious disease in a community at a particular time.

Escherichia coli (E. coli) A rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms. Most strains of E. coli are harmless but some can cause food poisoning.

Eugenics The belief and practice of improving the genetic quality of the human population.

Eukaryotic A single or multi-celled organism whose cells contain a nucleus and other membrane-bound organelles. Animals, plants, fungi and insects are eukaryotes.

Evolution Adaptation based on the process of natural selection. Successful organisms survive and reproduce while unsuccessful ones die off.

Exome All of the exons in a genome, which consist of the DNA that contains the instructions to make proteins.

Exon The part of a gene that has the instructions to make a protein.

Familial adenomatous polyposis An inherited condition that predisposes patients to early-onset colorectal cancer, and some other cancers.

Fertilisation When the sex cells (egg and sperm) meet and fuse together, combining the genetic material from mother and father and creating new life.

Flagella/flagellum A slender, whip-like structure that enables protozoa, bacteria, sperm etc. to move around.

Fluoresce/fluorescence The emission of light by a substance following exposure to light or radiation.

Foetus The unborn young of an animal still in the womb or egg.

Fragile-X syndrome An inherited form of intellectual disability caused by changes to the DNA sequence in the Fragile X mental retardation 1 (FMR1) gene on the X-chromosome.

Fungi/fungus A large group of organisms that includes yeasts, moulds and mushrooms. Fungi are distinct from plants, animals and bacteria because they have cell walls that contain chitin.

Gamete A male or female reproductive cell that contains half the genetic information for an organism. In humans the gametes are the sperm and egg cells.

Gene Section of DNA within the genome that carries the information to make a molecule, usually a protein. They contain the instructions for our individual characteristics, like eye and hair colour. In humans and other complex organisms, genes are split into coding (exons) and non-coding sequences (introns). These split sections allow some genes to make more than one type of protein.

Gene expression The process of making a functional product from the instructions in our DNA. The amount of functional product produced is referred to as the “level of expression”.

Gene mapping This is when scientists identify the locations of different genes on specific chromosomes, a bit like pointing out key landmarks on a geographical map.

Gene targeting This involves ‘knocking out’ a gene sequence from a genome and replacing it with an alternative gene sequence that has been generated in the lab.

Gene therapy The treatment of a disease by introducing modified DNA into the cells of the patient.

Generation time This is the average time between an organism being born and then producing offspring itself.

Genetic Of or relating to genes.

Genetic counselling Advice given to patients, prospective parents or their relatives before and after being tested for a genetic disease.

Genetic counsellor Health professionals who inform and support people faced with the possible diagnosis of a genetic disease. They help patients to understand the disorder, the likelihood of developing or transmitting it, and how it could be managed.

Genetic disease A disease that is caused by a change in an individual’s DNA (also known as a genetic disorder).

Genetic disorder A disease that is caused by a change in an individual’s DNA (also known as a genetic disease).

Genetic engineering / modification Refers to the direct manipulation of genes to alter an individual’s characteristics (phenotype) in a particular way.

Genetic screen Genetic screens are carried out to check for certain gene variants that could potentially increase the risk of disease in an individual.

Genetic testing A tool for identifying changes in DNA that could increase the risk of developing a disease.

Genetic variation This is differences in DNA. Variation between individuals in their DNA is what makes them different.

Genetic/gene variant A letter or region of a gene that is different in different individuals. The most common gene variants are single nucleotide polymorphisms (SNPs) where a single DNA base is altered. There can be numerous variants for any given gene.

Genetically modified (GM) crop A plant used in agriculture that has had its DNA changed by genetic engineering/modification.

Genetically modified (GM) food Food produced from a plant or animal that has had its DNA changed by genetic engineering/modification.

Genetically modified organism (GMO) An organism that has had its genome changed by direct manipulation of its genes in a way that does not happen normally in nature.

Genetics The study of genes and how certain characteristics are passed from one generation to the next.

Genome An organism’s complete set of genetic instructions. Each genome contains all of the information needed to build that organism and allow it to grow and develop. Our genome is approximately 3,000,000,000 base pairs long and is packaged into 23 pairs of chromosomes.

Genome editing A technique used to precisely and efficiently modify DNA within a cell. It can be used to add, remove, or alter DNA in the genome.

Genome-wide association study (GWAS) A study that compares areas of the genome that commonly vary in different individuals to see if they are associated with a particular disease or characteristic.

Genomics The study of the structure and function of genomes.

Genotype The genetic makeup of a cell, organism or individual.

Genotyping The process of determining the genetic makeup (genotype) of an individual by examining their DNA.

Genus

A group of closely related species. Scientific species names list the genus before the species

Germ cells The cells that develop into sperm and eggs.

Germline The genetic material being passed from generation to generation through the germ cells (sperm and egg).

Guanine One of the four nucleotide bases that make up DNA, pairs with cytosine.

Haemoglobin A protein that carries oxygen so as it can be transported around the body in our red blood cells.

Haemolymphatic The circulatory ‘tissue’, otherwise known as the blood and lymph.

Haemophilia Disorder characterised by slow and inefficient formation of blood clots leading to prolonged bleeding and spontaneous internal bleeding.

Haploid Term given to a cell with only one set of chromosomes, for example, the sex cells (sperm and egg).

Heart failure A condition when the heart can no longer pump enough blood around the body. It usually occurs when the heart muscle has become too weak or stiff to work efficiently.

Helicase Key enzyme involved in DNA replication, it is responsible for ‘unzipping’ the double helix structure by breaking the hydrogen bonds between bases on opposite strands of the DNA molecule.

Herbicide A type of chemical used to kill unwanted plants.

Hereditary haemochromatosis Also known as iron overload disease, it is an inherited disorder in which iron accumulates in the blood because too much is absorbed by the intestines.

Hereditary non-polyposis colorectal cancer A rare condition, but the most common inherited syndrome that predisposes people to early-onset colorectal cancer.

Hermaphrodite An organism that has both male and female reproductive organs.

Heterozygous An individual who carries two different alleles for a particular gene.

Histone A protein found in the nucleus of eukaryotic cells, which is involved in packaging DNA into structural units called nucleosomes.

Homologous recombination A process where DNA is exchanged between two identical or similar DNA molecules.

Homology When two DNA sequences are identical or similar to each other.

Homozygous An individual who carries two of the same alleles for a certain gene.

Hormone The body’s chemical messengers, carried in the bloodstream to tissues or organs. Important in many processes in the body, from reproduction to development.

Human Genome Project An international biological research project, launched in 1990, with the goal of sequencing the human genome for the first time and making the data freely available online.

Human immunodeficiency virus (HIV) A retrovirus that infects humans and attacks the immune system. Left untreated, HIV can lead to acquired immunodeficiency syndrome (AIDS).

Human papillomavirus (HPV) A group of viruses that infect your skin and the moist membranes lining your body, such as your mouth, throat and genitals. Cause abnormal tissue growth and genital warts.

Huntington’s disease A progressive neurodegenerative disorder, caused by a mutation in a single gene called huntingtin (HD), which usually develops in middle to late adult life. The mutation results in neuronal cell death in select areas of the brain and causes uncontrollable muscle spasms.

Hydrogen bonds An attractive interaction between two molecules. Hydrogen bonds hold the nucleotide bases (A, C, G and T) together in the DNA double helix.

Immune response Your body’s defence system that recognises and defends the body against pathogens such as bacteria and viruses.

Immunity The ability of an organism to resist a particular infection or disease due to having the specific antibodies or white blood cells needed to defend against it.

Inbreeding Reproduction resulting from the mating of a pair of individuals that are genetically closely related. Can lead to reduced fitness in a population.

Incubation time The time it takes between becoming infected with a disease and beginning to show symptoms.

Induced pluripotent stem cells A type of stem cell generated from an adult cell that has been reprogrammed to act like an embryonic stem cell.

Infectious disease Disease caused by a microorganism such as a virus, bacterium or parasite. They can be spread from one person to another.

Inflammation An immune reaction that results in localised redness, warmth and swelling. It generally occurs in response to an infection, irritation or injury.

Inheritance The process by which genes and characteristics are passed down from parent to offspring.

Insomnia The inability to sleep.

Insulin A hormone produced by the pancreas that regulates the amount of the sugar glucose in the blood. A lack of insulin or an inability to respond to insulin causes diabetes.

Intron Part of a gene that is not used to make protein and is cut out from the RNA between transcription and translation.

Ion An electrically charged particle formed when an atom loses or gains electrons.

Karyotype An image of all the chromosomes from an individual cell. Used to check for large-scale chromosome abnormalities.

Kilobase One thousand bases, or pairs of bases (1000 b or 1000 bp). In molecular biology, commonly used to describe the length of a DNA/RNA molecule.

Knockout Often done in model organisms, knockouts are when specific genes in an organism’s genome are inactivated. This allows scientists to understand more about the role of certain genes and what happens if they are absent.

Lagging strand The lagging strand is a single DNA strand that, during DNA replication, is replicated in the 5' - 3' direction (opposite direction to the replication fork). DNA is added to the lagging strand in discontinuous chunks called ‘okazaki fragments’.

Larvae The immature form of an organism, for example an insect, which will develop into something else in adulthood.

Leading strand The leading strand is a single DNA strand that, during DNA replication, is replicated in the 3’ – 5’ direction (same direction as the replication fork). DNA is added to the leading strand continuously, one complementary base at a time.

Leukaemia A type of cancer affecting the blood cells. It is named according to the type of white blood cell affected and whether it is chronic or acute.

Lumbar puncture A medical procedure where a large needle is inserted into the lower part of the spine. It is used to test for conditions and infections affecting the brain, spinal cord or other parts of the nervous system. Also called a spinal tap.

Lymph A colourless fluid containing immune cells that circulates through the lymphatic system and helps clear the body of foreign particles and unwanted cells.

Lymph gland Also known as a lymph node, a lymph gland is an oval-shaped organ that forms part of the lymphatic system. Lymph glands are located around the body, such as the armpit and stomach. They contain immune cells and are important for the proper functioning of the immune system, filtering out foreign particles and unwanted cells.

Lymphocytes Type of white blood cell important in the immune system. There are three subsets, T cells, B cells and natural killer cells.

Malaria One of the most common infectious diseases and a global public-health challenge. The disease is caused by protozoan parasites of the genus Plasmodium. Malaria parasites are transmitted by female Anopheles mosquitoes. The parasites multiply within red blood cells, causing symptoms including anaemia (light headedness, shortness of breath, racing heartbeat), and other general symptoms such as fever, chills, nausea, flu-like illness, and in severe cases, coma and death.

Malnutrition A condition resulting from a person not eating enough food or not eating the right foods to get necessary calories, protein, carbohydrates, vitamins or minerals.

Marker A gene or fragment of DNA with a known location on a chromosome. Markers can be used to establish the relative location of specific regions of the genome that might be of interest.

Megabase One million bases or base pairs (1,000,000 b or 1,000,000 bp). In molecular biology, commonly used to describe the length of a DNA/RNA molecule.

Meiosis Meiosis is a process where a single cell divides twice to produce four cells containing half the amount of genetic information as the original parent cell. These cells are our sex cells – sperm in males, eggs in females.

Messenger RNA (mRNA) Type of RNA molecule with an important role in protein synthesis. Involved in carrying genetic information from DNA to the ribosome in the cell where proteins are made.

Microbe (microorganism) A living organism that is too small to see with the naked eye, such as bacteria, fungi and protozoa. Some microbes cause disease.

Microbiome The full collection of genomes from all the microscopic organisms in a community or environment.

Mitochondria The power plants of our cells. Membrane-bound organelles found in most eukaryotic cells, they generate the cell’s source of energy.

Mitosis Mitosis is a process where a single cell divides into two identical daughter cells (cell division) with the same amount of genetic material as the original parent cell.

Model organism A model organism is a species that has been widely studied, usually because it is easy to maintain and breed in a laboratory setting and has particular experimental advantages.

Molecular biology A branch of biology that deals with the interactions between the molecules in our cells.

Monosomy When only one copy of a chromosome is present.

MRSA (methicillin-resistant Staphylococcus aureus) A form of staphylococcal infection that is resistant to a number of commonly used antibiotics.

Mucus A slippery substance secreted by the mucus membranes, for example the mouth and throat, that lubricates and protects the inner surfaces of the body.

Muscular dystrophy An inherited disorder that gradually causes the muscles to weaken.

Musculoskeletal The muscular and skeletal systems. Provides form, support, stability and movement to the body.

Mutant An organism resulting from or showing the effect of a genetic mutation.

Mutation A change that occurs in a DNA sequence. Mutations are relatively common in our DNA, but most have no detectable effect.

Natural selection The process where those organisms better adapted to their environment survive and pass on their beneficial characteristics to their offspring.

Neurodegenerative disease Range of conditions that affect the neurons in the human brain and cause progressive brain damage. Affect balance, movement, talking and memory. For example, Alzheimer’s disease and Parkinson’s disease.

Neurological Relating to the nerves and/or nervous system.

Neurotransmitter A chemical substance that transmits messages between nerve cells.

Non-coding DNA Sections of DNA that do not code for proteins. Although first called junk DNA it is now becoming clearer that much of this DNA has a function in controlling gene expression and chromosome structure. The amount of non-coding DNA varies amongst different species.

Non-coding RNA A functional RNA molecule that is transcribed from DNA but is not translated into a protein.

Non-myeloblative conditioning This involves the bone marrow being partially killed to supress the immune system. This may be done prior to a stem cell transplant, to avoid rejection.

Nucleosomes A level of DNA packaging present within chromosome. Nucleosomes are formed from a single length of DNA wrapped around a series of proteins called histones.

Nucleotide Building blocks of nucleic acids such as DNA and RNA. These are adenine, cytosine, guanine and thymine in DNA, and adenine, cytosine, guanine and uracil in RNA.

Nucleus A structure at the centre of all eukaryotic cells that contains the genome and acts as the ‘control room’ for the cell.

Obesity An abnormally high accumulation of body fat which can have a negative effect on health.

Oncogene A gene that normally directs cell growth. If mutated, an oncogene acts like a car accelerator stuck on drive, leading to uncontrolled cell growth, and cancer.

Open access The practice of providing unrestricted and free access to the results of research, often via the internet.

Organ A collection of cells and tissues that perform a specific function in the body.

Organelle A functional structure found within eukaryotic cells. Organelles carry out functions such as making proteins, processing chemicals and generating energy for the cell.

Ovary Reproductive gland in which the female reproductive cells, eggs, are produced.

Pancreas A gland located behind the stomach that secretes enzymes into the intestine to aid digestion. The pancreas produces the hormone insulin that regulates the absorption of sugar by cells.

Parasite An organism that lives in or on another organism and benefits at the expense of their host. Malaria is a type of parasite.

Parkinson’s disease A neurodegenerative condition in which part of the brain becomes progressively more damaged. Primarily affects movement leading to tremors and muscle stiffness.

Patent A patent is a right granted to an individual or company to protect inventions from being used or sold by other parties.

Pathogen An infectious agent that causes disease or illness to its host. Usually a bacteria, virus or parasite.

Peer review The evaluation of a piece of research by one or more people in the same field and of similar competence to the producers of the work.

Personal genomics An area of genomics focusing specifically on the sequencing and analysis of one person’s genome.

pH (chemistry) A measure of the acidity or alkalinity of a solution. A pH of 7 means the solution is neutral, below 7 is acidic, above 7 is alkaline.

Pharmacogenomics Tailoring a drug treatments to match a person’s genetic makeup – a form of ‘personalised medicine’.

Phenotype The physical traits and characteristics of an organism resulting from their genetic makeup.

Physiological The normal, healthy functioning of an organism’s body and organs.

Placebo A treatment that visibly resembles the experimental drug but has no effect on the individual. Used in clinical trials to provide a control test.

Placenta A temporary organ that develops in the uterus/womb of female mammals during pregnancy. It nourishes and maintains the unborn baby via the umbilical cord and is pushed out of the mother after birth.

Plasmid A small circle of genetic material, typically DNA in bacterial cells, physically separated from chromosomal DNA that replicates independently. Plasmids are used as vectors to transfer genes between cells.

Platelets A component of blood that is important in the clotting process. If a blood vessel is injured platelets change shape and stick together to form a blood clot.

Pluripotent A cell capable of developing into any type of cell or tissue in the body.

Pneumonia An infection of the lungs that causes the air sacs to fill with pus and other fluids. This makes it difficult for oxygen to be absorbed into the blood. It is commonly caused by viral or bacterial infections.

Point mutation A change in a single base-pair in a strand of DNA.

Pollen A powder produced by the male part of plants that contains plant sperm for reproduction.

Polymerase chain reaction (PCR) A technique to make large quantities of a specific fragment of DNA. It is often used in DNA testing and fingerprinting to amplify small amounts of DNA so that scientists have enough to work with.

Polypeptide A single chain of amino acids held together by peptide bonds. Proteins are made up of one or more polypeptide molecules.

Pre-implantation genetic diagnosis (PGD) A test for a genetic condition that is carried out on embryos created through IVF before they are implanted into the woman. It enables people with a family history of a genetic condition to ensure that only embryos without the genetic condition are used and that the risk of their child being unhealthy is reduced.

Predictive genetic testing Genetic tests designed to detect specific mutated genes to determine the likelihood of an individual developing a particular disease.

Prenatal ‘Before birth’.

Prenatal genetic testing Genetic tests carried out in the first, second and third trimesters to help determine whether a foetus has a disease or genetic abnormality, such as Down’s syndrome.

Primer A short strand of RNA that acts as a starting point for DNA replication.

Protein Large molecules made up of chains of amino acids. Proteins are essential to the functioning of our cells.

Radioactive Material that emits radiation energy.

Recessive When the allele of a gene shows its effect only if there are two copies in the genome, for example the allele for blue eyes.

Red blood cell Doughnut shaped cells found in the blood. They are responsible for carrying oxygen to all of the organs and tissues in the body.

Reference genome The genome sequence of an organism that is used as a representative example of the set of genes in the genome of that particular species. It can be used as a template for assembling and comparing individual genomes of the same species.

Retina A layer of tissue lining the inner surface of the eye that contains cells sensitive to light. These cells trigger nerve impulses that pass, via the optic nerve, to the brain, forming an image and enabling us to see.

Retrovirus A group of RNA viruses which insert a DNA copy of their genome into the host cell in order to replicate, for example, HIV.

Ribosome Small organelles found in our cells. They are responsible for assembling amino acids into proteins during protein synthesis.

RNA A nucleic acid similar in structure and properties to DNA, but it only has a single strand of bases and instead of the base thymine (T), RNA has a base called uracil (U).

RNA polymerase Small organelles found in our cells. They are responsible for assembling amino acids into proteins during protein synthesis.

Salmonella A group of bacteria that cause a wide spectrum of infectious diseases, including food poisoning and typhoid fever.

Sanger sequencing method The first DNA sequencing method, developed in 1977 by Fred Sanger and his team.

Selective breeding The process of breeding animals or plants to bring out particular desirable characteristics in future generations.

Semi-conservative Term to describe DNA after replication, DNA molecules consist of one brand new and one of the original chains of nucleotide bases.

Sequencing The method of determining the order of letters or bases in DNA, or the order of amino acids in a protein molecule.

Serotypes A group of closely related microorganisms distinguished by a common set of antigens.

Severe combined immunodeficiency (SCID) A genetic disorder characterised by a reduced number of immune cells. Can be treated with gene therapy.

Sex chromosome A chromosome that contains gender-specific genetic information. In humans, men have an X chromosome and a Y chromosome whereas women have two X chromosomes. Some genetic disorders are a result of changes in the sex chromosomes.

Sickle cell anaemia An inherited blood disorder in which red blood cells, which usually carry oxygen, develop abnormally.

Sigmoidoscopy Medical procedure where a doctor looks into the rectum and bowel of a patient using an instrument, inserted into the bottom, called a sigmoidoscope.

Single gene disorder Disorders caused by defects in one particular gene, and often have simple and predictable inheritance patterns.

Single nucleotide polymorphisms (SNPs) Most common type of genetic variation among people. They represent a change in a single DNA base (A, C, G or T) in the DNA code.

Somatic cells Any cell forming the body of an organism. Includes all cells except the sex cells/germ cells.

Species A group of closely-related organisms that have common physical and genetic characteristics and are able to interbreed to produce fertile offspring.

Spinal fluid A colourless liquid that is secreted from the blood into specific parts of the brain to help maintain the critical pressure within the brain and spinal cord.

Staphylococcus A group of infections caused by the bacterium Staphylococcus. The most common of this group of bacteria is Staphylococcus aureus.

Stem cells Cells that have the potential to develop into many different cell types in the body during early life and growth.

Streptococcus Any type of infection caused by the group of bacteria Streptococcus. Infections vary in severity from mild throat infections to pneumonia.

Stroke Serious medical condition that occurs when the blood supply to part of the brain is cut off and brain cells are damaged or die.

Susceptibility The likelihood of being vulnerable to a particular thing, for example, a genetic disease.

T-cell Subset of lymphocyte white blood cell that play a central role in human immunity.

Telomerase This is an enzyme that adds the DNA sequence repeat TTAGGG, also known as telomeres, to the ends of chromosomes.

Telomeres Sections of DNA found at the ends of each of our chromosomes, consisting of the same sequence of bases repeated over and over. They protect the ends of chromosomes by forming a cap.

Terminator A version of DNA base (A, C, G or T) that stops the DNA sequencing reaction when it binds to the DNA strand.

Therapeutic Relating to the treatment, curing or healing of a condition or disease.

Thymine One of the four nucleotide bases that make up DNA, pairs with adenine.

Tissue A group of specialised cells that work together to perform a specific function in the body.

Trait A distinguishing quality or characteristic. A disease trait may be a particular symptom that signals a specific disease.

Transcription The first step during protein synthesis when the DNA in a gene is copied to produce an RNA transcript called messenger RNA (mRNA).

Transfer RNA (tRNA) A carrier molecule important in protein synthesis. It is responsible for reading the instructions held by DNA and then carrying amino acids to the ribosome ready to make a protein as instructed.

Transgenic An organism that contains additional, artificially-introduced genetic material in every cell.

Translation The second step during protein synthesis where the message from DNA for making a protein has been taken to the ribosome and a protein is constructed with the help of tRNA.

Trimester A period of three months often used to describe the stages of a human pregnancy.

Trisomy When three copies of a chromosome is present. Down’s syndrome is the result of trisomy.

Tsetse fly A blood-sucking fly in Africa that bites both humans and animals, transmitting African trypanosomiasis (sleeping sickness).

Tuberculosis A bacterial infection caused by the bacterium Mycobacterium tuberculosis. It mainly affects the lungs but can spread to other parts of the body, such as the bones or nervous system.

Tumour suppressor gene A gene that halts cell division to prevent the formation of a cancerous tumour. If mutated they can act like a broken brake, allowing cell division to occur at an uncontrollable rate.

UK National DNA Database A database holding the DNA profiles and samples of UK individuals. It is the largest database of its kind in the world and is continuing to grow each year.

Uracil One of the four nucleotide bases that make up RNA (instead of thymine), pairs with adenine.

Vaccine A biological preparation that is given to an individual to stimulate their immune system so that it will recognise a particular pathogen in the future. A vaccine usually contains a small amount of the pathogen so that the body will recognise it as foreign and produce antibodies against it.

Vector A vehicle for delivering genetic material, such as DNA, into a cell. Useful in genetic engineering. Often a bacterium.

Vertebrate Animals with backbones.

Virus Small infectious agent that replicates only inside the living cells of other organisms. Can infect all life forms from animals, to plants. Influenza is a virus.

White blood cell Cells with a key role in the immune system, defending the body against disease and infection. There are a number of types of white blood cell, including lymphocytes.

Womb/uterus A hollow, pear-shaped organ located in a women’s lower abdomen. This is where a baby develops during pregnancy.