: A liquid solution of ions such as sodium or potassium. Most liquids in the body are electrolytes. enzyme: A protein that serves as a chemical catalyst, accelerating the rate at which a biochemical reaction occurs. eugenics: The study or practice of human improvement through genetic control or genetic engineering. eukaryotes (“true nucleus”): Organisms whose DNA is surrounded by a membrane and which possesses organelles. Eukaryotes are a “superkingdom” of life forms that include most terrestrial plants and animals other than bacteria.
gamete: A male or female reproductive cell (sperm or ovum). These combine during fertilization to form a zygote.
gene: A sequence of DNA nucleotides, located in a particular spot on a particular chromosome, that encodes a specific instruction to a cell.
gene-cloning: The process of duplicating genes inside modified bacteria.
gene therapy: Genetic engineering performed on a fetus, child, or adult to repair defective genes.
genetic engineering or gengineering: Deliberate manipulation of DNA and genes in order to alter an organism’s genome.
genetics: The study of the patterns of heredity, the traits that an organism inherits from its ancestors.
genome: All the genetic material carried by individuals of a given species, containing the molecular instructions for inheritable features.
genotype: The specific genome of an individual; the combination of alleles the individual carries.
germ cells: The basic reproductive cells of a multicellular organism; see gamete. germline gengineering: Genetic engineering of the germ cells so that an organism will develop in a different way than its unmodified genome would have indicated.
haploid: Having only one copy of each chromosome. Fungi and some algae are haploid organisms. Plant and animal gametes are also haploid.
hormone: A protein that acts as a chemical messenger within the body. There are many different hormones, each with its own function.
in vitro (“in glass”): Taking place outside a living organism, usually used when referring to “test tube” fertilization or to the process of growing an organism in an artificial womb, clone tank, etc.
intron: A segment of DNA within a gene that does not code for protein sequences and that is edited out when the gene is expressed. Introns may have regulatory or structural uses.
ligase: An enzyme that can rejoin DNA fragments together, used as a tool in genetic engineering.
microbe: A single-celled organism, like a bacterium or alga. Usually microscopic, but colonies of single-celled organisms can be large enough to see.
mitochondrion (plural: mitochondria): An organelle that converts organic chemicals into a usable energy supply. It also contains DNA, separate from the chromosomes, inherited through the female line.
monoclonal antibody: An antibody grown in a cloned cul- ture, producing usable amounts of identical antibodies.
nanomachine: A microscopic organic or inorganic robot, usually cell-sized or smaller.
nanotech or nanotechnology: An emerging technology based around the manipulation of atoms and molecules using microscopic machines. In biotechnology, nan- otech promises the ability to precisely manipulate cells and genes.
necrosis: The abnormal death of cells, caused by injury or infection.
nucleotides: The basic molecular subunits of DNA or RNA. Thousands of nucleotides make up DNA molecules; their sequence determines the genetic code and the function of each gene.
organelle: A structure bound by the cell membrane in eukaryotic organisms, such as the mitochondria.
pathogen: An organism (usually a microbe) or chemical that causes a disease. PCR: See polymerase chain reaction.
peptide: A short chain of amino acids, which may combine with other peptides to form a protein.
phenotype: The expression of a genotype in physical features of an organism. plasmid: A ring-shaped structure of DNA, found in bacteria.
polymerase chain reaction (PCR): A means of rapidly copying DNA using specialized enzymes and equipment.
prion: A pathogenic protein capable of “hijacking” cells to produce copies of itself. Prions can produce various brain diseases such as BSE (“mad cow disease”) and kuru (“laughing sickness”) as well as pathologies of aging and senility.
protein: A large molecule made up of long chains of amino acids. Proteins are formed by cells as directed by their genes, and are the basis for the structure and function of living things. There are countless different kinds of proteins, each with its own specialized function.
protozoan: A single-celled microscopic animal somewhat more complex than a bacterium.
recombinant DNA: The basis of genetic engineering, this is the technology of cutting DNA molecules into discrete pieces and recombining them with other DNA molecules to form new genes.
ribonucleic acid (RNA): A chemical similar in structure to DNA. One type, messenger RNA (mRNA), relays the orders from genes to the molecular machinery of cells, while other types perform other roles. Because of its ability to tell a cell what to do, RNA is a primary tool of gengineers.
ribosome: Parts of the cell’s molecular machinery, these are “factories” that create proteins under orders from the genes.
RNA: See ribonucleic acid.
telomerase: An enzyme that increases the number of telomeres on the ends of achromosome.
telomere: A member of a repetitive DNA sequence at the end of a chromosome that serves as a buffer against incomplete copying.
tissue engineering: The design of artificial organic tissue. transgenic: A transgenic organism is one that has genes added to it from outside its original species.
virus: A non-cellular biological organism that can repro- duce only within a host cell. Viruses consist of RNA or DNA covered by protein. RNA viruses are especially useful tools for gengineering.
zygote: A cell formed when two gametes combine in sexual reproduction. Zygotes grow into blastocysts, embryos, and ultimately adult organisms.