1. in vascular plants, a slightly enlarged portion of a stem where leaves and buds arise and where branches originate. 2. in a circular DNA superhelix, the point of contact in a figure-of-eight; if the left strand in the upper part of 8 is closest to the viewer at the node, it is called a positive node; if the left strand in the upper part of 8 is in back of the other strand at the node, it is called a negative node. 3. in a cladogram (q.v.), a point where one branch splits off from another. Each node represents a common ancestor, and the branches are the lineages derived from it. Also called a divergence node.
Subjects: Genetics and Genomics.