Constitutive - organism is said to be constitutive for the production of an enzyme or other protein if that protein is always produced by the cells under all physiological conditions See inducible.

Constitutive enzyme - an enzyme that is synthesised continually regardless of growth conditions cf inducible enzyme; repressibe enzyme.

Constitutive gene - a gene that is continually expressed in all cells of an organism

Constitutive promoter - an unregulated promoter that allows for continual transcription of its associated gene

Constitutive synthesis - continual production of RNA or protein by an organism

Contaminant - bacterial, fungal or algal micro-organism accidentally introduced into a culture or culture medium Contaminant may overgrow the plant cells and consequently inhibit their growth Working under aseptic conditions with a rigorous exclusion of potential contaminants must be practised in plant tissue culture.

Conting - a set of overlapping clones that provide a physical map of a portion of a chromosome.

Contiguous map - the alignment of sequence data from large, adjacent regions of the genome to produce a continuous nucleotide sequence across a chromosomal region.

Continuous culture - a suspension culture continuously supplied with nutrients by the inflow of fresh medium The culture volume is normally constant If batchculture; closed continuous culture; continuous fermentation; open continuous culture.

Continuous fermentation - a process in which cells or micro-organisms are maintained in culture in the exponential growth phase by the continuous addition of fresh medium that is exactly balanced by the removal of cell suspension from the bioreactor cf continuous culture.

Continuous variation - variation not represented by distinct classes Phenotypes grade into each other, and measurement data are required for analysis Multiple genes are usually responsible for this type of variation aka quantitative variation cf discontinuous variation.

Control - 1 noun: unchanged (standard) protocol or treatment for comparison with the experimental treatment The term is commonly used for untreated orgarusms.
2 verb: to direct or regulate cultures with addition of plant growth regulators.

Controlled environment - the environment in which parameters, such as light, temperature, relative humidity and sometimes the partial gas pressure, are fully controlled.

Controlling element - in eukaryotes, transposable elements which control the activity of standard genes A controlling element may, in the simplest case, inhibit the activity of a gene through becoming integrated in, or close to, that gene Occasionally, either in germinal or somatictissue, it may be excised from this site, and due to excision the activity of the gene is more or less restored, while the element may become reintegrated elsewhere in the genome where it may affect the activity of another gene For example, in maize, a cotrolling element such as Ac or Ds is capable of influencing the expression of a nearby gene.

Conversion - the development of a somatic embryo into a plant.

Coordinate repression - correlated regulation of the structural genes in an Operon by a molecule that interacts with the operator sequence.

Co polymers - mixtures consisting of more than one monomer; for example, polymers of two kinds of organic bases, such as uracil and cytosine (poly-DC) have been combined for studies of the genetic code.

Copy DNA see cDNA copy number - the average number of molecules of a plasmid or gene per genome contained in a cell.

Co repressor - an effector molecule that forms a complex with a repressor and turns off the expression of a gene or set of genes.

Corpus - the corpus is found below the tunica (qv) and is a part of the apical meristem In the corpus, cells divide in all directions, giving them an increase in volume See apicalmeristem.

Correlation - a statistical association between variables.

Cortex - primary tissue of a stem or root, bounded externally by the epidermis and internally in the stem by the phloem and in the root by the pericycle.

Cos ends - the 12-base, single-strand, complementary extensions of bacteriophage lambda (1) DNA aka cos sites.

Co segregation - when two genetic conditions appear to be inherited together.

Cosmid - a plasmid vector which contains the two cos (cohesive) ends of phage lambda and one or more selectable markers such as an antibiotic resistance gene Cosmids exploit certain properties of phage lambda to enable large, 4050 kb, DNA fragments to be cloned at high efficiency Cosmids and cosmid recombinants replicate as plasmids.

Cot curve - when duplex DNA is heated, it dissociates into single strands When the temperature is lowered, complementary strands tend to anneal of re-nature The extent of renaturation depends on the product of DNA concentration in moles of nucleotides per litre, and time in seconds A graph showing the proportion of re-natured DNA against cot is known as a cot curve The cot at which half the DNA has re-natured is the half-cot, a parameter indicating the degree of complexity of the DNA.

Co transfection - in baculovirus expression systems, the procedure by which the baculovirus and the transfer vector are simultaneously introduced into insect cells in culture.