A strategy using a genetic construct that is a kind of mutagen that acts as a cellular marker. If the construct integrates into a gene that is transcribed in a specific cell type at a specific time, the marker will be expressed in those cells at that time. In essence, it disrupts genes throughout the …
Category Archives: Uncategorized
Gene
The functional unit of inheritance based upon the coding of DNA molecules, and occupying a fixed locus on a chromosome (see figure below), which directs the synthesis of a particular protein. It consists of a sequence of base pairs that correspond to a specific sequence of amino acids constituting a protein. Genes function to build …
Gene flow
the exchange of genes among populations or species either by means of migration, or less directly by the diffusion of genes over many generations. Gene flow tends to limit the establishment of genetic distinctiveness. While it is relatively rare in isolated populations, when it happens it can be a highly significant event such that it …
Gender identity disorder (GID)
A strong and persistent lack of comfort with one’s sex (e.g., an individual with male reproductive structures who feels psychologically like a female). In childhood, it is evident in a child’s insistence that he or she is the wrong sex, persistent preferences for clothing, games and pastimes of the other sex, and taking on cross-sex …
Gender
Originally used in grammar to classify nouns as feminine, masculine or neuter, it has also become a term to denote the social meanings of masculine and feminine. Thus, while sex is biological, gender is socially constructed or determined, and its meaning can change from place to place and over time. It has become an analytical tool …
Gender identity
Psychological feeling or personal conception that one is either male or female (in relatively rare cases, it may be both or none). Common in all societies, it thus appears to be a universal phenomenon, but its determinants are complex. They may be portrayed as consisting of exposure to prenatal hormone levels, influences emanating from the …
Gastrulation
The developmental process in which the cells of the blastula are reorganized by folding and migration into the blastocoele, resulting in an embryo with three distinct layers of cells (see figure below). These primary germ layers consist of the ectoderm (outer), mesoderm (middle), and entoderm (inner). The developmental biologist Lewis Wolpert penned a pithy sentence about …
Ganglia
Group of nerve cells (outside or inside the central nervous system) conveying information from the environment (touch, temperature, vision), or from the body (muscle length), to a group of nerve cells in the spinal cord (autonomic ganglion) connecting preganglionic and postganglionic nerve fibers of the autonomic nervous system. See Autonomic nervous system (ANS), Central nervous …
Gastrula
A cup- or basin-shaped structure (the archenteron), later an elongated one, formed by the invagination of a blastula and that begins with the formation of the three germ layers. See Blastopore, Blastula, Ectoderm, Embryogenesis, Gastrulation, Germinal (or germ) layers
Gamma (γ) motoneuron
One of two types of somatic motoneurons that innervate intrafusal muscle fibers found within the muscle spindle. They regulate the sensitivity of the spindle to muscle stretching, thus enabling intrafusal fibers to contract (and shorten). When gamma neurons are activated, intrafusal muscle fibers contract such that only a small stretch is required to activate spindle …