Cholesterol
A steroid that forms an essential component of animal cell membranes and acts as a
precursor molecule for the synthesis of other biologically important steroids.
Chondrichthyes
The vertebrate class of cartilaginous fishes, represented by sharks and their relatives.
Chondrin
A protein-carbohydrate complex secreted by chondrocytes; chondrin and collagen fibers
form cartilage.
Chordate
A member of a diverse phylum of animals that possess a notochord; a dorsal, hollow nerve
cord; pharyngeal gill slits; and a postanal tail as embryos.
Chorion
The outermost of four extraembryonic membranes; contributes to the formation of the
mammalian placenta.
Chorionic villus sampling (CVS)
A technique for diagnosing genetic and congenital defects while the fetus is in the uterus. A
small sample of the fetal portion of the placenta is removed and analyzed.
Chromatid
Either of the two strands of a replicated chromosome, which are joined at the centromere.
Chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is
not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a
light microscope.
Chromista
In some classification systems, a kingdom consisting of brown algae, golden algae, and
diatoms.
Chromoplasts
A plastid contains pigments other than chlorophyll, usually yellow or orange carotenoids.
Chromosomes
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of
one very long DNA molecule and associated proteins.
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