Adenine (A):
One of the four letters of the genetic alphabet; nitrogenous base and the essential component of nucleic acid.

Allele:
Applied to the varied forms that may be assumed by the same gene situated at the same ‘locus’ (level) and that confers different characteristics on the species concerned.

Amino Acids:
The ‘molecular building blocks’ that make up the proteins. There are 20 different kinds. The sequence of amino acids is the linear order by which they are linked to the protein.

Antibodies (or immunoglobulins):
Proteins produced by the blood of mammals that are mobilized in response to an attack on the body by a viral, bacterial, or tumoural aggressor.

Antigen:
Substance foreign to the body that arouses the immune defense system. It stimulates the production of antibodies capable of reacting specifically with the antigen.

Antisense:
A nucleic acid molecule that is complementary to a messenger RNA. Antisense molecules are used to block expression of the gene encoded by the mRNA.

Bacteria:
Unicellular microbes.

Bacteriophage:
A virus that attacks bacteria. Bacteriophage lambda is frequently used as a vector in recombinant gene experiments.

Base:
The ‘letters’ of the genetic code, A, G, T, and U are called ‘bases’.

Biocatalyst:
The acceleration of biochemical reactions by enzymes.

Biochemistry:
The chemical reactions taking place within a living organism.

Bioconversion:
Chemical conversion making use of a biocatalyst or enzyme.

Bioreactor:
Apparatus for the large-scale propagation of cells. Also called a fermenter.

cDNA (Complementary DNA):
A DNA molecule that is complementary to a messenger RNA.

Cell Fusion:
The formation of a hybrid cell, produced by fusing two cells of different species.

Chimera:
Name for any new organism produced by genetic engineering.

Chromosome:
The physical structure containing the genes. Each species has a specific number of chromosomes – 23 pairs in the case of human beings.

Clone:
Line stemming from a single ancestral cell.

Codon:
Group of three bases in DNA and RNA that determines the position of an amino acid in ‘building’ a protein.

Coding Sequence:
The part of a gene that defines the amino acid sequence of the encoded protein.

Cytoplasm:
The part of the cell outside of the nucleus.

Cytosine (C):
A base; one of the four letters in the genetic alphabet.

Diploid:
Said of a cell or organism in which all types of chromosomes are represented twice. All cells in higher species, except gametes (sexual cells) are diploids.

DNA (deoxyribonucleic acid):
The basic biochemical component of the chromosomes and the support of heredity, which contains the sugar deoxyribose.

DNA Polymerase:
An enzyme that adds a nucleotide to a DNA chain. Used in DNA replication.

Enzymatic Engineering:
Techniques used to manipulate the properties of enzymes. Also called protein engineering.

Enzymes:
Proteins that act as a catalyst in biochemical reactions. They are produced by living cells.

Eucaryote:
Cell possessing a nucleus isolated from the rest of the cell by a membrane: yeasts, protozoans, fungi, and certain algae.

Gene:
The basic unit of heredity, which plays a part in the expression of a specific characteristic. The expression of a gene is the mechanism by which the genetic information that it contains is transcribed and translated to obtain a protein.

Gene Therapy:
The use of normal DNA to correct a genetic defect.

Genetic Engineering:
A technique used to modify the genetic information in a living cell, reprogramming it for a desired purpose (such as the production of a substance it would not normally produce).

Genetic Marker:
Specific identifiable and localized DNA sequence. A genetic marker can be detected by hybridization with a complementary probe or by its phenotype expression.

Genome:
The genetic identity card of an individual: the combination of chromosomes constituting the hereditary material.

Genomics:
The cataloguing, sequencing, and study of all the genes in the genome of a particular organism.

Genotype:
The genetic makeup of an organism.

Glycoprotein:
Protein to which groups of sugars become attached.

Glycosylation:
The attachment of groups of sugars to a molecule, such as protein.

Guanine (G):
Base in the genetic code.

Haploid:
Referring to a cell or organism in which each chromosome is present but a single time. This is above all true of the gametes (sexual cells).

Heterozygote:
A diploid cell (with a double set of chromosomes) whose paternal and maternal alleles are different.

Hormones:
The ‘chemical messengers’ of the body.

Hybridization:
The annealing or pairing of two strands of nucleic acid by complementary base pairing.

Hybridoma:
Hybrid cells resulting from the fusion of myeloma cell (immortal) and a lymphocyte (cell producing antibody).

In Vitro:
Biological reactions taking place in a laboratory, in an artificial system, outside a living being.

In Vivo:
An experiment that takes place within a living cell or organism.

Karyotype:
The characteristic arrangement of an individual’s chromosomes, arranged in pairs.

Liposome:
A little ‘bag’ consisting of a membrane of lipids used to contain substances to be transported within the body or fused with a living cell in culture.

Locus:
The location (or level) of a gene on a chromosome.

Lymphocyte:
Cell that plays an essential role in immune mechanisms. Nearly one fourth of the white cells are lymphocytes.

Meiosis:
Cellular division, with a passage from the diploid stage to the haploid stage during the formation of sexual cells.

Metabolism:
The combination of physical and chemical processes that occur in cells and organisms, with the production of metabolites or energy.

Mitosis:
Cellular division at the end of which, each cell has the same number of chromosomes as the original cell. This takes place in several phases: anaphase, metaphase, prophase, and telophase.

Molecular Weight:
The sum of the atomic weights of the atoms constituting a molecule, expressed in ‘molecule-grams’ (or ‘moles’).

Molecule:
A group of atoms united by a chemical bond.

Monoclonal Antibodies:
Highly specific antibodies derived from a single cellular clone. Produced by Hybridoma cells.

Multigene:
A single characteristic expressed by several genes.

Mutagenesis:
The induction of genetic mutation by physical or chemical means to obtain a characteristic desired by researchers.

Mutation:
Fortuitous or induced event leading to the hereditary alteration of the genotype.

Nucleic Acids:
Organic acids of the cell nucleus consisting of sequences of bases. There are two kinds depending upon the kind of sugar of which they are made: ribose (RNA) or deoxyribose (DNA).

Nucleotide:
One of the four bases (A, C, G, and T) to which a sugar and a phosphate are attached.

Oligonucleotides:
Short segments of DNA or RNA.

Oncogene:
The gene of cancer.

Organic (compound):
Molecules containing carbon.

Peptide:
Short chain formed of a succession of amino acids.

pH:
Abbreviation for ‘potential hydrogen’. It is a measure of acidity or alkalinity of a solution, with a scale ranging from 0 (acid) to 14 (alkaline), and which reflects the activity of the hydrogen ion in the solution. Below 7, pH is acid; above that, is alkaline.

Phage:
Abbreviation for ‘bacteriophage’.

Phenotype:
The observable properties of an organism resulting from the interaction between its genotype and the environment.

Plasmid:
The circular chromosome of bacteria that reproduces itself independently of the principle chromosome. A choice vector in genetic engineering.

Polysaccharide:
A long chain formed of sugar molecules, like starch or cellulose.

Probe:
A DNA or RNA sequence marked by radioactivity, fluorescence, or enzymatically for use in genetic screening by hybridization.

Procaryote:
Cell or organism without a nucleus separated by a membrane. The chromosomes are bathed directly in the cytoplasm. Bacteria is an example.

Protein:
Macromolecule consisting of amino acids connected by peptide bonds. Proteins are considered the ‘building blocks’ of living beings.

Replication:
The formation of two new strands of DNA from existing DNA, permitting the reproduction of an identical new cell as the result of the division.

Restriction Site:
A DNA sequence targeted by a restriction enzyme; an enzyme capable of recognizing a specific sequence in DNA and cleaving the DNA at that site.

RNA (Ribonucleic Acid):
The basic biochemical component of chromosomes and support of hereditary containing ribose sugar.

Thymine (T):
Base in the genetic code.

Transcription:
The first stage in the expression of a gene by means of messenger RNA.

Translation:
Second stage in the expression of a gene: a synthesis of the amino acids in a specific order, corresponding to the sequence of the nucleotides of a messenger RNA.

Uracil (U):
Base in the genetic code.

Validation (Gene Validation):
The assignment of a specific function (or functions) to individual genes.

Vector:
A DNA molecule used to introduce foreign genetic information into a host cell.

Virus:
An infectious agent containing a single type of nucleic acid, DNA or RNA enclosed in a ‘cloak’ of proteins or protein lipids (capsids). The virus lives as a parasite on the living cells and will only multiply within them. Viruses are classified in several groups depending on their structure or properties: adenovirus (a virus with DNA), retrovirus (with RNA), etc. Used as vectors in gene cloning.