Glossary 319 



Canalization a description of developmental pathways, usually thought 

 of as resulting from buffering. 



Carotenoids fat soluble pigments ranging in color from yellow to red; 

 most are tetraterpenes. 



Centric fragment a portion of a chromosome that contains a centromere. 



Centriole a cytoplasmic organelle of characteristic fine structure with 

 which the spindle and astral fibers are associated during cytokinesis 

 and karyokinesis. 



Centromere the portion of a chromosome, usually greatly restricted in 

 length, to which spindle fibers are attached in cell division. Syn.: kine- 

 tochore. 



Centrosome the area surrounding the centriole in many cells, presum- 

 ably associated with the organization of protein fibers. 



Character any feature that varies within the group of items under study. 



Character displacement condition in which sympatric populations of 

 two species are more dissimilar than allopatric populations of the same 

 two species. 



Chemosynthetic able to elaborate carbohydrate substances of relatively 

 high complexity with only inorganic substances (e.g., sulfur, iron) as 

 a source of energy. 



Chiasma, chiasmata a cross-shaped configuration of the chromosomes in 

 a bivalent in the first meiotic prophase, usually the visible icsult of 

 prior cytological crossing-over. 



Chlorophyll magnesium complexes of porphyrins found as green pig- 

 ments in the cells of photosynthetic organisms where they absorb light 

 energy. 



Chromatid a visible subdivision of a chromosome having but one centro- 

 mere (or behaving as if the centromere were undivided); a half chro- 

 mosome. 



Chromatograph the result of treating a substance or mixture with one 

 or more solvents to dissolve differentially and separate one or more 

 constituents of the substance. 



Chromonema the finest visible longitudinal morphological subdivision 

 of a chromosome. 



Chromosome the cell organelle with which most of the nuclear genetic 

 information is associated and which contains the centromere or spindle 

 attachment point. 



Chromosome complement the set of chromosomes included in a nucleus 

 which may include one or more genomes, depending upon the cell and 

 its state. 



Cilium, -ia a short protoplasmic extension with characteristic fine struc- 

 ture, projecting from a cell and moving with a characteristic pattern 

 and beat; usually present in large numbers. 



Cisternae apparent spaces within the endoplasmic reticulum whose 

 profiles in electron micrographs suggest they are flattened vesicles. 



Cis state two mutational alterations in the same cistron or on the same 

 chromosome; as opposed to the trans state, q.v. 



