biology-dictionary_11-06-2009

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Clonal selection
The mechanism that determines specificity and accounts for antigen memory in the immune
system; occurs because an antigen introduced into the body selectively activates only a tiny
fraction of inactive lymphocytes, which proliferate to form a clone of effector cells specific
for the stimulating antigen.
Clone
(1) A lineage of genetically identical individuals or cells.
(2) In popular usage, a single individual organism that is genetically identical to another
individual.
Cloning vector
An agent used to transfer DNA in genetic engineering, such as a plasmid that moves
recombinant DNA from a test tube back into a cell, or a virus that transfers recombinant
DNA by infection.
Closed circulatory system
A type of internal transport in which blood is confined to vessels.
Cnidaria
Phylum Cnidaria includes animals like hydras; polyps; jellyfishes; sea anemones; corals
Cnidocyte
A stinging cell containing a nematocyst; characteristic of cnidarians.
Cnidarians
Cnidarians are the group of invertebrate animals which possess stinging cells called
cnidocytes
Cnidoblast
A cell in the epidermis of coelenterates in which a nematocyst is developed.
Cocci
Any spherical or nearly spherical bacteria
Cochlea
The complex, coiled organ of hearing that contains the organ of Corti.
Codominance
A phenotypic situation in which both alleles are expressed in the heterozygote.

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