Glossary

Definitions of selected terms

32P (Phosphorous-32)
32P (Phosphorous-32) is a radioactive isotope that is commonly deployed to label biological molecules. The marker is particularly helpful in the identification of malignant tumours because cancer cells tend to accumulate more phosphate than normal cells.
35S (35 Sulfur)
35S is a low energy beta emitter that is often used as a radioactive label for biological molecules. It can be detected using Geiger–Müller counter and liquid scintillation counting techniques.
5S ribosomal RNA
5S ribosomal RNA (5S rRNA) is an integral component of the large ribosomal subunit in all known organisms. It has approximately 120 nucleotide-long ribosomal RNA molecules. The term 5S refers to the molecule's sedimentation velocity in an ultracentrifuge. The exact function of 5S rRNA is unclear, but it is believed to enhance protein synthesis by stabilising the ribosome scaffold.
8M urea
8M urea is an organic compound which is used extensively in proteomics and molecular biology. It is particularly helpful in making fixed brain tissue transparent to visible light while retaining fluorescent signals from labelled cells. The adoption of 8M urea for this purpose allowed for much deeper imaging of neuronal processes than with previous methods which involved the use of conventional one photon or two photon confocal microscopes.
Acinetobacter baumannii
Also known 'Iraquibacter', this is a type of bacteria that commonly causes ventilator-associated pneumonia and blood-stream infection in critically ill patients with compromised immune systems.
Acrylamide gel
A gel that contains an acrylamide solution. Commonly used in electrophoresis, the gel provides a mesh-like matrix that makes it possible to accurately separate proteins based on their length in an easy and inexpensive process.
Active immunity
This is a type of immunity that is acquired so as to built up resistance to disease. Such immunity can be acquired either by having the disease or through vaccination against it.
Active site
This is a part of a protein that must be maintained in a particular shape if the protein is to function.
Adjuvant
A pharmacological or immunological agent that is added to enhanced the effect of other agents. In the case of vaccines an adjuvant maybe added to boost the immune response to produce more antibodies and longer-lasting immunity, thereby reducing the dose of antigen required.
Agglutinin
This is an antibody that can recognise and bind to an immunological determinant on the surface of bacteria or other cells which causes them to clump (agglutination).
Allele
One of two or more versions of a gene. Most organisms inherit two alleles for each gene, one from each parent. Where the two alleles inherited are the same, the term homozygous is used for that gene. If the alleles are different, the term heterozygous is used. Originally the term allele was used to describe variation among genes, but it can now also refer to variation among non-coding DNA sequences.
Allelic exclusion
This describes the process by which only one immunoglobulin light chain and one heavy chain gene get transcribed in any one cell while the other genes get repressed.
Allergen
A substance, usually a protein, that can stimulate an abnormal immune response in the body, or what is known as an allergic reaction. Allergens come from a variety of sources, including dust mite excretion, pollen and pet dander.
Allergy
An abnormal reaction by the body's immune system after exposure to a particular substance, often a protein, contained a particular food, pollen, fur, or dust.
Amino acid
The building blocks that cells in the body use to build proteins. Each protein contains hundreds, even thousands of amino acids joined together in a specific sequence in chain-like formation. The order of the amino acids determines a protein's shape and
Autoradiogaphy
A technique using x-ray film to detect and visualise the distribution of radioactive substances in a molecule.
Autoradiograph (autoradiogram)
An image showing the location of radioactive substances in an object.
B lymphocytes
Also known as B cells, B lymphocytes are a type of white blood cell that is responsible for the production of antibodies which stick to receptors on the surface of germs and other foreign substances and alert the immune system to the presence of intruders. B cells develop from stem cells in the bone marrow.
Bacillus thuringiensis (Bt)
This is a gram positive species of bacteria that dwells in soil. Such bacteria are useful in agriculture because they produce toxins that are deadly to some pests. Different types of Bt target different insect groups. The targets include beetles, mosquitoes, black flies, caterpillars, and moths. Some crops have been genetically engineered to produce Bt toxins.
Bacteriophage (phage)
A bacteriophage, or phage, is a virus that infects and replicates within a bacterium. There are various types of bacteriophages, including R17, lambda, f1, phi X 174 and M13.
Base pairs (bases)
Pair of complementary nucleotides in DNA.
Biotechnology
Biotechnology refers to the use of cellular and living organisms or their components, including genes, to develop products that improve human health, food and the environment.
Burkitt's lymphoma
A type of blood cancer that is most common in equatorial Africa and New Guinea.
cDNA library
A library that contains cloned complementary DNA fragments inserted into a collection of host cells, each of which has been inserted into a DNA vector (e.g. a circular DNA plasmid) and replicated in a bacterium like E. coli. The bacteria provide a pool of cDNA's for use in different experiments. Each bacteria population contains a single inserted cDNA which can be extracted and amplified using PCR.
Chromatography
A chemical technique used for separating the components of a mixture. During the test a mixture dissolved in a liquid or gas is passed through a column, paper or glass support, where the elements of the mixture are either absorbed or hindered to varying degrees and thereby become separated. The technique is used both for the purification and collection of components as a means to quantify and measure component parts in a mixture.
Chromosome
Thread-like structure made up of a tightly coiled single strand of DNA located inside the nucleus of a cell. Usually found in pairs, chromosomes are involved in the transmission of hereditary information. They work in tandem with other nucleic acids to build proteins and are also involved in cell division.
Clone
A genetic replica of a cell or organism that has been created without sexual reproduction.
Cloning technique
A method to produce genetically identical copies of a biological entity.
Codon
A set of consecutive, non-overlapping triplets of nucleotides.
Colorimetry
A technique that measures the concentration of a chemical element with the aid of a colour reagent.
Complement
A soluble protein found in blood serum that is responsible for killing bacteria. The protein was originally called 'alexin' when it was discovered in the late 19th century, but the term was subsequently changed to reflect the fact its action 'complements' that of an antibody in the destruction of bacteria.
Complementary DNA (cDNA)
A DNA copy of a messenger RNA (mRNA) molecule produced by reverse transcription. The term is used to reflect the fact that its sequence is a complement of the original mRNA sequence. Scientists often use cDNA deployed in gene cloning or as gene probes or in the creation of a cDNA library. Some viruses also use cDNA to convert their viral RNA into mRNA which allows viral proteins to take over the host cell.
Constitutively active gene
A gene that is always transcribed, regardless of any regulatory influences.
Cytomegalovirus
One of eight viruses in the herpes family. This virus commonly infects humans but is largely harmless. Symptoms include a sore throat, swollen glands and a high temperature.
Cytoplasm
A fluid-filled space between the cell nucleus and the outer membrane.
Degradation method
A technique developed by Fred Sanger where a large molecule is broken down, usually with enzymes, into smaller fragments and then pieced together to work out the sequence of the molecule's building blocks.
Deoxyribonuclease (DNAase)
An enzyme that cuts up DNA.
Dideoxynucleotide (dideoxy)
A compound that inhibits the action of DNA polymerase and blocks its attachment of nucleotides to a growing DNA chain.
Dideoxynucleotide triphosphate (ddTTP)
An analogue of a normal DNA polymerase substrate.
Disulfide bridges
Chemical bonds that link two peptide chains together.
DNA
This stands for DeoxyriboNucleic acid, which is a complex chemical found in the nucleus and mitochondria of a cell. It provides the genetic instructions needed for an organism to develop, survive and reproduce.
DNA polymerase
DNA polymerase is a type of enzyme that can be found in all living organisms. There are many types of DNA polymerase. Some help replicate DNA when a cell divides and others help in the day-to-day repair and maintenance of DNA.
DNA sequencing
A biochemical method to determine exact order of the four building blocks, nucleotide bases, that make up a piece of DNA.
Double-helix
Term used to describe the spiral configuration of DNA.
Double-stranded
A molecule that consisting of two bound strands, each of which complements the other. DNA is usually double-stranded.
Electrophoresis
An analytical method that uses an electric current to separate and sort out molecules based on their size. The method takes advantage of the charged particles in the molecules.
Enzyme-linked immunosorbent assay (ELISA)
A method that uses antibodies to detect specific proteins.
Epstein Barr Virus (EBV)
One of eight viruses in the herpes family, this virus is known to cause glandular fever and some forms of cancer and auto-immune diseases in humans.
Escherichia coli
A type of bacteria that commonly live in the intestines of people and animals. There are many types of Escherichia coli. Most pose no harm to human health, but one group produces a potent toxin which can cause food poisoning.
Expressed sequence tag (EST)
A particular stretch of DNA within a coding region of a gene that is used to identify full-length genes. Such tags are used as landmarks in gene mapping.
Fluorodinitrobenzene (DNFB or FDNB)
Also called Sanger's reagent, dinitrofluorobenzene, DNFB or FDNB, is a chemical that reacts with the N-terminal amino acid of polypeptides. It is used to sequence proteins.
Fractionation
A separation process that divides a certain quantity of a mixture into a number of smaller quantities.
Free amino acids
Singlular molecules not bound by peptide bonds to other amino acids.
Gene
A distinct stretch of DNA that codes for proteins that perform the cellular functions in an organism. It is the basic physical and functional unit of hereditary. Genes vary in size. Each person has two copies of each gene, one inherited from each parent.
Gene expression
The process by which genetic instructions in DNA are converted into a functional product, such as a protein.
Gene flow
Also known as gene migration or allele flow, describes the transfer of genes from one individual or population to another genetically compatible individual or population. The process enables genetic diversity among populations.
Gene mapping
Also called linkage mapping, gene mapping describes the method used to identify the position of a gene and the distances between genes. Gene mapping is used to find genes responsible for relatively rare, single-gene inherited disorders such as cystic fibrosis and Duchenne muscular dystrophy. Scientists are also using the method to work out what genes are involved in the development of more common disorders like asthma, heart disease, diabetes, cancer, and psychiatric conditions.
Gene transcription
The process by which cells read out the genetic instructions in their genes to RNAs, such as messenger RNA, which is the first phase in the synthesis of proteins.
Genetic engineering
Also called genetic modification or genetic manipulation, genetic engineering involves the introduction, elimination or rearrangement of specific genes to change the genetic makeup of an organism.
Genetic mutation
A change that happens in the DNA sequence. Such a change can occur either when mistakes are made in the process of copying DNA or result from environmental factors, such ultraviolet radiation from the sun or cigarette smoke. Some mutations are only carried in an individual organism. A change can carried into the organism's offspring where the mutation occurs in a germline cell.
Genetically heterogeneous
Where more than one genetic factor can cause similar characteristics. Within the clinic genetic heterogeneity means the presence of a variety of genetic defects which cause the same disease. These can result from mutations at different places on the same gene. Many cancers and genetic disorders, like type-I diabetes, are genetically heterogeneous.
Genetically modified organism (GMO)
Any organism that has had its genes altered through genetic engineering.
Genetics
A branch of science that studies how physical and behavioural characteristics, including medical conditions, are passed down from parents to offspring through genes.
Genome
Complete set of genetic material within the single cell of an organism.
Genomic library
A large collection of DNA fragments that have been cloned from a given organism, tissue, organ, or cell type. Such libraries can contain complete genomic sequences or complementary DNA sequences. They provide the starting point for sequencing whole genomes like the human genome.
Genomics
A branch of genetics established in the 1980s directed towards studying the structure, function, evolution and mapping genomes in organisms.
Genotype
The set of genes in DNA which is responsible for a particular trait.
Germline cell
A reproductive cell (egg or sperm cell) that contains half the set amount of chromosomes.
Glycoprotein
A molecule that consists of a carbohydrate and a protein..
Gramicidin
Gramicidin was one of the first antibiotics to be clinically tested and manufactured commercially. It was first isolated from the soil bacterium Bacillus brevis by the French-born American microbiologist René Dubos in 1939 with the help of Rollin Hotchkiss. The antibiotic inhibits the growth of Gram-positive bacteria.
Gramicidin S
An antibiotic that was discovered in 1942 by the Russian microbiologist Georgyi Frantsevitch Gause and his wife Maria Brazhnikova. The antibiotic is effective against some gram-positive and gram-negative bacteria and some fungi.
Haemagglutinin (H)
A type of protein molecule found on surface of a virus particle that enables a virus to enter host cells.
Haemoglobin
A protein molecule present in red blood cells that delivers oxygen to cells in the body.
Homochromatography
Type of chromatography that rests on the displacement of oligonucleotides (small groups of nucleotides) fixed on some ion-exchange paper by some unlabelled oligonucleotides.
Human Genome Project (HGP)
International research effort officially launched in 1990 and completed in 2003 to determine all three billion bases of DNA within the entire human genome and its genes.
Hybrid
An animal or plant that has been produced through cross-breeding two different species or plant varieties.
Hybrid cell
Where a cell is formed by combining two cells of different origin in which the two nuclei merge into one.
Hydrolysis
The process by which chemical bonds in a molecule are broken down through the addition of water or another substance such as an acid.
Insulin
A hormone secreted by the pancreas that helps the body regulate sugar levels in the blood.
Intellectual property rights
Rights given to a person or company for an invention, including new technologies or new organisms. Such rights allow the owner to control their use and to earn rewards from their use.
Ion
An electrically charged atom formed by the loss or gain of one or more electrons.
Ionophoresis (Ion exchange chromatography)
A separation process that relies on charge-charge interactions between proteins in a sample and charges immobilized on resin.
Lymphoma
Type of blood cancer.
Lysine
Essential nutrient in the human diet.
Messenger RNA (mRNA)
A molecule in cells that conveys genetic information from DNA to the ribosome, the site of protein synthesis.
Metabolism
The chemical reactions that occur in a living cell or organism to build and break down substances.
Methicillin-resistant Staphylococcus aureus (MRSA)
A bacterial species that is resistant to many widely used antibiotics.
Methionine
Type of amino acid.
Mitochondria
Specialised subunits present in the cytoplasm of cells that provide energy to the cell.
Mitochondrial DNA
Most DNA is contained within a cell's nucleus, but it can also be found in mitochondria. Unlike nuclear DNA, which is inherited from both parents, mitochondrial DNA is only passed on by the mother.
Mitosis
A cell replication process in which a single cell divides to become two identical cells.
Molecular biology
A branch of science that studies the composition, structure, function and interactions of cellular molecules, such as proteins and nucleic acids.
Mycobacterium tuberculosis
Type of microorganism that causes tuberculosis.
Myoglobin
A protein found in heart tissue and other muscles.
Nasopharyngeal carcinoma
Cancer of the throat and nose.
Neuraminidase
Type of enzyme that facilitates the release of new virus particles from infected host cells.
Nucleic acid
Long molecule made up of smaller molecules called nucleotides which are chemically linked together in a chain. Nucleotides are instrumental in transferring genetic information from one generation to another. There are two types of nucleic acids: deoxyribo
Nucleic acid hybridisation
The process in which two complementary strands of nucleic acids - RNA, DNA or oligonucleotides - are joined.
Nucleotides
Nucleotides are molecules present in all cells of the body. They serve many purposes, including acting as cellular messengers between the outside and the inside of a cell's nucleus, storing energy and as physiological mediators. Nucleotides are also necessary to the construction of the nucleic acids DNA and RNA. DNA is made up of four base nucleotides: adenine (A), cytosine (C), guanine (G) and thymine (T). RNA is made up of A, G, and C, plus uracil.
Octanucleotide
DNA fragment made up of eight nucleotides.
Oligonucleotide
Commonly made in the laboratory, an oligonucleotide is a short sequence of DNA (usually 2-50 bases). Oligonucleotides are important in artificial gene synthesis, polymerase chain reactions, DNA sequencing, library construction and can be used as molecular probes.
Open reading frame (ORF)
Describes a continuous stretch of DNA which starts with the start cordon (groups of three nucleotides) and ends with any of the termination stop codons. The start codon is usually AUG and the stop codon is usually UAA, UAG or UGA. The term is deployed in work to find genes.
Patent
A patent is a form of intellectual property rights granted by a government to an inventor or their assignee for a limited amount of time in exchange for the public disclosure of the invention. A patent provides the right to exclude all others from making, using, or selling an invention or products made by an invented process. Like any other property right, it may be sold, licensed, assigned or transferred, given away or simply abandoned.
Peptide
A compound made up of two or more amino acids linked together in a chain.
Peptide bond
A chemical bond between two amino acid molecules.
Pharmacogenomics
The discipline that investigates the relationship between genetics and a person's response to a drug.
Phenotype
The physical characteristics of an organism that result from the interactions between genes, environment, disease, molecular mechanisms, and chance.
Plus minus technique
A technique developed by Sanger for sequencing DNA, which involves the use of DNA polymerase to add and exclude one trinucleotide to DNA chains and the end products, labelled with a radioactive tag, then being separated with electrophoresis on acrylamide
Polymerase chain reaction (PCR)
A technique that is used to copy a specific DNA sequence. The technique provides the means to make one billion exact copies of an original target DNA within a couple of hours.
Polypeptide chain
Chain of amino acids.
Primer
Template strand of DNA used to generate a new double-strand of DNA.
Promoter
A region of DNA that regulates the level of function of other genes. (Source: US Department of Agriculture)
Protein
Proteins are large complex molecules that do most of the work in the cells in a living organism. They play a crucial role in almost all biological processes, being involved in building, maintaining and replacing tissues in the body, as well helping to pro
Recombinant DNA
Also known as gene cloning or splicing, recombinant DNA is a technique that produces identical copies (clones) of a gene. The procedure involves joining together DNA segments in a cell-free system (e.g. in a test tube outside living cells or organisms). The recombinant DNA molecule is then introduced into a cell where it will replicate itself, either as an independent entity (autonomously) or as an integral part of a cellular chromosome.
Regulatory gene
A gene the controls the expression of one of more structural genes. It does this either directly by DNA binding or indirectly by activating a cellular protein.
Restriction enzymes
These are DNA-cutting enzymes found in and harvested from bacteria. Each enzyme recognises and cuts DNA at a particular point on its nucleotide chain.
Reverse transcription
The process of copying of an RNA molecule back into its DNA complement. This is done with the help of an enzyme called reverse transcriptase. In nature retroviruses use reverse transcription to insert themselves into an organism's genome. In the laboratory reverse transcription is used to translate unstable mRNA molecules into stable cDNA.
Ribonuclease T1
Enzyme that cuts nucleic acids at a very specific point on a nucleotide chain.
Ribonucleic Acid (RNA)
A chemical substance made up of nucleotides compound of sugars, phosphates, and derivatives of the four bases adenine (A), guanine (G), cytosine (C), and uracil (U). RNAs function in cells as messengers of information from DNA that are translated into protein or as molecules that have certain structural or catalytic functions in the synthesis of proteins. RNA is also the carrier of genetic information for certain viruses. RNAs may be single or double stranded. (Source: US Department of Agriculture)
Ribonucleic acid (RNA)
A type of molecule that plays a role in the coding, decoding, regulation and expression of genes. There are two types of RNA: 1) messenger RNA (mRNA), responsible for carrying the genetic code to the ribosome to build a protein; and 2) transfer RNA (tRNA)
Ribonucleotide triphosphates
RNA precursors.
Ribosome
A minute particle found in the cytoplasm of living cells which is responsible for assembling the proteins of a cell.
Ribosubstitution method
Means to substitute a specific deoxynucleotide with a specific ribonucleotide in the DNA chain. The method facilitates a DNA chain to be cleaved at very specific points with an enzyme.
Selectable marker
A gene, often encoding resistance to an antibiotic or an herbicide, introduced into a group of cells to allow identification of those cells that contain the gene of interest from the cells that do not. Selectable markers are used in genetic engineering to facilitate identification of cells that have incorporated another desirable trait that is not easy to identify in individual cells. (Source: US Department of Agriculture)
Serine proteases
Enzymes that cleave peptide bonds in proteins.
Sickle-cell anaemia
An inherited disorder that distorts the shape of red blood cells, making them fragile and prone to rupture, causing severe anaemia.
Site directed mutagenesis (SDM)
Technique that makes it possible to very precisely change part of an organism’s DNA.
Somatic cell
Any cell in the body that is not a reproductive cell. The somatic cell carries two sets of chromosomes, one inherited from each parent.
Staphylococcus aureus
Bacterial species that is the cause of many different health problems in humans, including carbuncles, food-poisoning, and infections around medical devices and wounds.
Tetranucelotides
A particular block of nucleotides made up of four base pairs (adenine (A) and thymine (T), cytosine (C) and guanine (G).
Transgene
A gene that has been taken from one organism and inserted into another organism.
Transgenic organism
An organism that has had its genes deliberately altered to give it specific characteristics it would not otherwise possess naturally.
Two-dimensional paper fraction technique
Method developed by Sanger and colleagues in 1965 to determine the sequence of nucleic acids. It used a combination of radioactive labelling and electrophoresis and laid the groundwork for sequencing RNA.
Vector (molecular biology)
A vector in molecular biology is a vehicle that is used carry foreign genetic material from one cell into another where it can be replicated and/or expressed. Typically a vector is a DNA sequence that consists of an insert (transgene) and a larger sequence that serves as the 'backbone' of the vector. The most common form of vector used in genetic engineering are plasmids. (Source: US Department of Agriculture)
Viron
Virus particle.
Whole genome sequencing (WGS)
Laboratory process to determine the complete DNA sequence of an organism's genome.
X-ray crystallography
A technique used to determine the atomic and molecular structure of a crystal based on the use of X-rays.