More food, cleaner food – gene technology and plants
Glossary
amino acid. The basic building block of protein. All amino acids contain an amino (NH2 ) end, a carboxyl end (COOH) and a side group (R). In proteins, amino acids are joined together when the NH2 group of one forms a bond with the COOH group of the adjacent amino acid. The side group is what distinguishes each of the amino acids from the others. There are 20 common amino acids: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.
antisense gene. A gene which produces RNA molecules complementary to the normal messenger RNA of the target gene. Antisense genes prevent expression of the target gene and are used to selectively turn off production of certain proteins.
bacterium (plural bacteria). A single-celled, microscopic organism without a distinct nucleus.
base (in DNA). Any one of four nitrogenous (nitrogen-containing) bases (adenine, thymine, guanine and cytosine). The sequence of the bases in DNA determines the sequence of amino acids in all proteins found in living things.
chromosome. A long DNA molecule that contains the genes of the organism. Chromosomes are visible in cells during cell division.
clone. A group of organisms, cells or DNA sequences derived from the same ancestor.
DNA (deoxyribonucleic acid). The nucleic acid forming the genetic material of all organisms with the exception of some viruses which have RNA. DNA is present in the nucleus and other organelles such as mitochondria and chloroplasts.
DNA fingerprinting. Identification of the DNA of different individuals based on variation that exists between them in the sequence of bases in the DNA.
enzyme. A protein that acts as a catalyst. Every chemical reaction in living organisms is facilitated by an enzyme.
gene. The basic unit of inheritance. A gene is a segment of DNA that specifies the structure of a protein or an RNA molecule.
gene probe. A specific sequence of single-stranded DNA or RNA, usually labelled with a radioactive atom. A probe is designed to bind to, and therefore single out, a particular segment of DNA to which it is complementary.
gene technology. The techniques used in the manipulation of DNA to alter the genetic make-up of organisms.
genetically modified organism. An organism with genetic material that has been altered using gene technology.
genetics. The study of heredity and variation in organisms. It can also refer to the genetic features of an organism.
genome. The total genetic material of an individual or species.
marker gene. An easily identified gene that is inserted into the organism, along with the desired gene. The presence of the marker gene tells researchers that the transformation was successful.
nutrient agar plate. A sterile, enclosed dish with a layer of a jelly-like substance containing complete food requirements for growth of bacteria, other small organisms or cells. If the bacteria are well-spaced when they are introduced to the plate, each bacterium will produce a colony of bacteria.
pathogen. An organism capable of causing a disease.
plasmid. A small, circular DNA molecule. Bacteria can have plasmids in addition to the DNA of the main chromosome. Foreign DNA can be added to plasmids. The modified plasmid then transports the DNA into a new cell.
protein. A large molecule composed of a linear sequence of amino acids. This linear sequence is a protein's primary structure. Short sequences within the protein molecule can interact to form regular folds (eg, alpha helix and beta pleated sheet) called the secondary structure. Further folding from interaction between sites in the secondary structure forms the tertiary structure of the protein.
Proteins are essential to the structure and function of cells. They account for more than 50 per cent of the dry weight of most cells, and are involved in most cell processes. Examples of proteins include enzymes, collagen in tendons and ligaments and some hormones. More information can be found at Protein structure and diversity (Molecular Biology Notebook, Rothamsted Research, UK).
restriction enzyme. Restriction enzyme is a shorthand way of saying restriction endonuclease. (Nuclease = an enzyme that cuts a nucleic acid; endo = cuts in the middle, not at the ends; restriction = cutting is restricted to specific sites.) Therefore it is an enzyme that cuts the DNA molecule at specific locations along its length. Each type of restriction enzyme recognises a particular base sequence of the DNA and cuts precisely at the same point each time. (For example, the restriction enzyme EcoR1 recognises the sequence GAATTC, and cuts between the G and its adjacent A. The complementary strand of DNA has the sequence CTTAAG, and here also the enzyme cuts between the A and the G.)
RNA (ribonucleic acid). A nucleic acid similar to DNA. In most organisms, RNA serves as a ‘read-out’ of the genetic information in DNA to facilitate various aspects of cell metabolism, particularly as a message for protein synthesis. However, in some viruses, including influenza, RNA is the primary genetic material instead of DNA, and is more prone to mutation than DNA. For more information see RNA (Nobelprize.org).
species. Living things of the same kind that are potentially capable of breeding and producing fertile offspring. Theoretically, plants or animals of different species cannot interbreed. However, occasionally this does not hold true.
virus. A submicroscopic infectious agent consisting of a nucleic acid (DNA or RNA) molecule surrounded by a protein coat. Viruses cannot replicate outside a living cell. More information can be found at How viruses work (How Stuff Works, USA).
Page updated August 2006.