Darwin's children

Immune response (immunity, immunization):the provoking and marshaling of defensive cells within an organism to ward off and destroy pathogens, disease-causing organisms such as viruses or bacteria. Immune response may also identify nonpathogenic cells as foreign, not part of the normal body complement of tissues; transplanted organs cause an immune response and may be rejected. Autoimmune diseases such as multiple sclerosis and various forms of arthritis may occur or reoccur in response to viral activation due to stress. In humans, ERV activation has been suggested as a cause of some autoimmune diseases.

Intron:region of DNA that generally does not code for proteins. In most eukaryotic cells, genes consist of mingled exons and introns. Introns are clipped out of transcribed messenger RNA (mRNA) before it is processed by ribosomes; ribosomes use the code contained in lengths of mRNA to assemble specific proteins out of amino acids. Bacteria lack introns.

Lipids:organic compounds such as fats, oils, waxes, and sterols. Lipids make up many of the structural components of cells, including much of the cell wall or membrane.

Lipome:the total complement of lipids within a cell. Lipids may also form alliances with sugars and proteins (see glycomeand proteome).

Mitochondrion, mitochondria:organelles within cells that process sugars to produce the common fuel for cells, adenosine triphosphate, or ATP. Generally regarded as highly adapted descendants of bacteria that entered host cells billions of years ago. Mitochondria have their own loops of DNA constituting a separate genome within every cell. Mitochondrial DNA, being shorter and simpler, is often the target of choice for fossil analysis.

Modern human: Homo sapiens sapiens.Genus Homo,species sapiens,subspecies sapiens. Homo sapiens sapienscould be read as “Man who is wise, who knows.” Also, “Man who is discreet, who savors.”

Mobile element:movable segment of DNA. Transposonscan move or have their DNA copied from place to place in a length of DNA using DNA polymerase. Retrotransposonscontain their own reverse transcriptase, which gives them some autonomy within the genome. Mobile elements have been shown by Barbara McClintock and others to generate variety in plants; but some believe these are, more often than not, so-called selfish genes which are duplicated without being useful to the organism. More and more, geneticists have found strong evidence that mobile elements contribute to variation in all genomes and help to regulate both embryonic development and evolution.

Mutation:alteration in a gene or segment of DNA. May be accidental and unproductive or even dangerous; may also be useful, leading to the production of a more efficient protein. Mutations may lead to variation in phenotype, or the physical structure of an organism. Random mutations are usually either neutral or bad for the health of the organism.

Neandertal: Homo sapiens Neandertalensis.Possibly ancestral to humans. Modern anthropologists and geneticists are currently engaged in a debate about whether Neandertals are our ancestors, based on evidence of mitochondrial DNA extracted from ancient bones. More than likely, the evidence is confusing because we simply do not yet know how species and subspecies separate and develop.

Pathogen:disease-causing organism. There are many different varieties of pathogen: viruses, bacteria, fungi, protists (formerly known as protozoa), and metazoans such as nematodes.

PERV:Porcine endogenous retrovirus. Ancient retroviruses found in the genome of pigs. See ERV.

Phage:a virus that uses bacteria as hosts. Many kinds of phages kill their hosts almost immediately and can be used as antibacterial agents. Most bacteria have at least one and often many phages specific to them. Phages and bacteria are always in a contest to outrun each other, evolutionarily speaking.

Phenotype:the physical structure of an organism or distinctive group of organisms. Genotypeexpressed and developed within an environment determines phenotype.

Pheromone:a chemical message produced by one member of a species that influences the physiology and the behavior of another member of the same species. Whether or not this chemical message is consciously detected (smelled), pheromones have the same effect. Mammalian pheromones, in the form of “social odors,” that one member of a species is exposed to during interaction with another member of the species, cause changes in hormone levels and in behavior. See vomeropherin.

Polyploidy:see chromosome.

Protein:genes often code for proteins, which help form and regulate all organisms. Proteins are molecular machines made up of chains of twenty different types of amino acids. Proteins can themselves chain or clump together. Collagen, enzymes, many hormones, keratin, and antibodies are just a few of the different types of proteins.

Proteome, Proteomics:the total complement of proteins within a cell or group of cells, or in an individual organism as a whole. Different tissues will produce different proteins from a standardized set of genes; gene activation in different tissues at different times causes variation in a cell's proteome. Knowing which genes have been activated can be traced through identifying proteins and other gene products. (See glycomeand lipidome.)

Provirus:the genetic code of a virus while it is contained within the DNA of a host.

Radiology:imaging of the interior of a body using radiation, such as X-rays, PET scans (positron emission tomography), MRI (Magnetic resonance imaging), CAT scans (Computerized axial tomography), etc.

Recombination:exchange of genes between or within organisms or viruses. Sexual reproduction is one such exchange; bacteria and viruses can recombine genes in many different ways. Recombination can also be done artificially in a laboratory.

Retrotransposon, retroposon, retrogene:see movable elements .

Retrovirus:RNA-based virus that inserts its code into a host's DNA for later replication. Replication can often be delayed for years. AIDS and other diseases are caused by retroviruses.

RNA:ribonucleic Acid. Intermediate copy of DNA; messenger RNA (mRNA) is used by ribosomes as templates to construct proteins. Many viruses consist of single or doubled strands of RNA, usually transcribed to DNA within the host.

SHEVA:fictional human endogenous retrovirus that can form an infectious virus particle, or virion; an infectious HERV. No such HERV is yet known. In Darwin's Radioand this novel, SHEVA carries first-order instructions between individuals for a rearrangement of the genome that produces a new variety of human. In effect, SHEVA triggers preexisting genetic “set-asides” that interact in time-proven ways to create a subtly different human phenotype.

Sequencing:determining the sequence of molecules in a polymer such as a protein or nucleic acid; in genetics, discovering the sequence of bases in a gene or a length of DNA or RNA, or in the genome as a whole. Research into the sequence of the entire human genome has made huge strides, but our understanding of the implications of this growing knowledge is in its infancy.

Sex chromosomes:in humans, the X and Y chromosomes. Two X chromosomes results in a female; an X and a Y results in a male. Other species have different types of sex chromosomes.

Shiver:hypothetical activation of dormant endogenous retroviruses in women who have undergone SHEVA pregnancies. Recombination of exogenous and endogenous viral genes may produce new viruses with an unknown pathogenic potential.