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  Home >> Molecular Biology Dictionary >>Co-integrate-vector-system, Comparative gene mapping

Co-integrate vector system
A two-plasmid system for transferring cloned genes to plant cells.  The cloning vector has a T-DNA segment that contains cloned genes.  After introduction into Agrobacterium tumiefasciens, the cloning vector DNA undergoes homologous recombination with a resident disarmed Ti plasmid to form a single plasmid carrying the genetic information for transferring the genetically engineered T-DNA region to plant cells

Co-integrate
A DNA molecule formed by the fusion of two different DNA molecules, usually mediated by a transposable element.

Colchicine
(L. colchicum, meadow saffron, from colchis, ancient Mingrelia). An alkaloid obtained from Colchicum autumnale, autumn crocus or meadow saffron, which inhibits spindle formation in cells during mitosis, so that chromosomes cannot separate during anaphase, thus inducing multiple sets of chromosomes.  Also used to halt mitosis at metaphase - the stage when chromosomes are most visible.

Coleoptile
Protective sheath covering the shoot apex of the embryo in monocotyledenous plants. It protects the plumule as it emerges through the soil.

Coleorhiza
(Gr. koleos, sheath + rhiza, root) A protective sheath surrounding the radicle of monocotyledenous plants

Co-linearity

A relationship in which the units in one molecule in the same sequence as the units in another molecule which they specify; e.g., the nuc1eotides in a gene are co-linear with the  amino acids in the polypeptide encoded by that gene.

Collection
In PGR: see base collection; active collection

Collenchyma
(Gr. kolla, glue + enchyma, a suffix, derived from parenchyma and denoting a type of cell tissue) A tissue of living cells, the walls being unevenly thickened with cellulose and hemicellulose, but never lignified; it functions in mechanical support in young, short-lived or non-woody organs and is thus found in midribs and leaf petioles.

Colony hybridization
A technique that uses a nucleic acid probe to identify a bacterial colony with a vector carrying a specific cloned gene or genes

Colony
1. An aggregate of identical cells (clones) derived from a single progenitor cell.
2. A group of interdependent cells or organisms.

Combinatorial library
During the ligation reaction with cDNAs of light and heavy antibody chains into a bacteriophage lambda (1) vector, many novel combinations consisting of one heavy and one light chain coding region are formed. The library comprises these combinations, each in a separate vector.

Commensalism
The interaction of two or more dissimilar organisms where the association is advantageous to one without affecting the other(s). cf parasitism; symbiosis.

Companion cell
Living cell associated with the sieve cell of phloem tissue in vascular plants.

Comparative gene mapping
The comparison of map locations of genes between species. The results of these comparisons indicate substantial conservation of blocks of genes and even large segments of chromosomes between species.  Great use can be made of this conservation of map position.  For example, in the case of "mammals, it means that if a gene has been mapped in one or both of the intensely-mapped species (humans and mice), then the likely location of that gene in other mammals can be predicted with considerable confidence.  Conversely, if a mapped anonymous DNA marker has an effect on a quantitative trait (this being indicative of the marker being linked to a quantitative trait locus (QTL)) in, say, cattle, then knowledge of the comparative map between cattle and humans can identify genes in the homologous region of the human genome that could correspond to the QTL.  Such genes are called comparative positional candidate genes (q.v.).

 

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