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

Correlation
A statistical association between variables.

Cosmid
1. A plasmid vector which contains the two cos (cohesive) ends of phage lambda (Lamda) and one or more selectable markers such as an antibiotic resistance gene. Cosmids exploit certain properties of phage lambda (Lamda) to enable large, 40-50 kb, DNA fragments to be cloned at high efficiency. Cosmids and cosmid recombinants replicate as plasmids. 2. A type of vector used for cloning 35-45 kb of DNA. These are plasmids carrying a phage Lamda cos site (which allows packaging into Lamda capsids), an origin of replication and an antibiotic resistance gene. A plasmid of 40 kb is very difficult to put into bacteria, but can replicate once there. Cosmids, however, have a cos site, and thus can be packaged into (Lamda) allow efficient introduction into bacteria (you’ll have to look up the cos site elsewhere).

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

Co-transformation
In genetic engineering experiments, it is often necessary to transform with a plasmid for which there is no selectable phenotype and then screen for the presence of that plasmid within the host cell. Co-transformation is a technique in which host cells are incubated with two types of plasmid, one of which is selectable and the other not. Cells which have been transformed with the first plasmid are then selected. If transformation has been carried out at high DNA concentration, then it is probable that these cells will also have been transformed with the second (non-selectable) plasmid. The technique is frequently used in experiments with mammalian cells.