Gastrula. Stage of embryonic development of an animal, succeeding beastula, when the gastrulation movements occur.

Gastrulation. Embryological term for the complex of cell movements which occurs in almost all animals at the end of the cleavage period.

Gel. It is quasi solid state of a colloidal matter.

Gamma. Organ of vegetative reproduction in mosses and liverworts; consisting of a small group of cells of varying shape and size that becomes detached from the parent and develops into a new plant; often formed in groups, in receptacles known as gemma-cups.

Gemmation.
Kind of asexual reproduction by formation of a group of cells (a gemma in plants) which develops into a new individual, or a new member of a colony of connected individuals. It may develop before or after it separates (completely or partially) from its parent. Occurs in many liverworts, mosses, coelenterates, ascidians. Commonly called budding in animals.

A gene may be defined as the shortest length of chromosome that cannot be broken by recombination (see meiosis) or that can undergo mutation, both units being recognized as a single base pair in the nucleotide sequence that makes up the DNA.
The gene as a unit of function may be defined as the sequence of nucleotides concerned with the synthesis of a single polypeptide chain, corresponding to a particular sequence of the genetic code One or more of these structural genes, coding for protein, may be associated with a controlling operator gene; this unit is known as an operon. The operon itself is controlled by a third type of gene, the regulator gene.

Genecology. Study of genetical composition of plant populations in relation to their habitats.

Gene Exchange.
Production of fertile offspring possessing new combinations of parental genes that occurs within a breeding population. Used by biosytematists in determining and defining limits of population units