Cladogram A branching diagram that illustrates hypotheses about the evolutionary relationships among groups of organisms. Cladograms can be considered as a special type of phylogenetic tree that concentrates on the order in which different groups branched off from their common ancestors. A cladogram branches like a family tree, with the most closely related species on adjacent branches.

Class
A category of taxonomic classification between order and phylum, a class comprises members of similar orders. See taxon.

Classification
The arrangement of organisms into hierarchical groups. Modem biological classifications are Linnaean and classify organisms into species, genus, family, order, class, phylum, kingdom, and certain intermediate categoric levels. Cladism, evolutionary classification, and phenetic classification are three methods of classification.

Clinical Heterogeneity
The production of clinically different phenotypes from mutations in the same gene.

Clone
An exact copy made of biological material such as a DNA segment (e.g., a gene or other region), a whole cell, or a complete organism.
2. A group of genetically identical cells or organisms that are descened from one parent. In molecular biology, a copy of DNA sequences created by recombinant DNA techniques.
3. Organisms or cells that are genetically identical.
4. A set of genetically identical organisms asexually reproduced from one ancestral organism.