G1 phase Gap 1 phase of the eukaryotic cell-division cycle, between the end of mitosis and the start of DNA synthesis. (Figure 17–4)
G1-Cdk Cyclin–Cdk complex formed in vertebrate cells by a G1-cyclin and the corresponding cyclin-dependent kinase (Cdk). (Table 17–1, p. 969)
G1-cyclin   Cyclin present in the G1 phase of the eukaryotic cell cycle. Forms complexes with Cdks that help govern the activity of the G1/S-cyclins, which control progression to S phase.
G1/S-Cdk Cyclin–Cdk complex formed in vertebrate cells by a G1/S-cyclin and the corresponding cyclin-dependent kinase (Cdk). (Figure 17–11 and Table 17–1, p. 969)
G1/S-cyclin Cyclin that activates Cdks in late G1 of the eukaryotic cell cycle and thereby helps trigger progression through Start, resulting in a commitment to cell-cycle entry. Its level falls at the start of S phase. (Figure 17–11)
G2 phase Gap 2 phase of the eukaryotic cell-division cycle, between the end of DNA synthesis and the beginning of mitosis. (Figure 17–4)
G2/M transition Point in the eukaryotic cell cycle at which the cell checks for completion of DNA replication before triggering the early mitotic events that lead to chromosome alignment on the spindle. (Figure 17–9) ganglioside   Any glycolipid having one or more sialic acid residues in its structure. Found in the plasma membrane of eukaryotic cells and especially abundant in nerve cells. (Figure 10–16) gap gene In Drosophila development, a gene that is expressed in specific broad regions along the anteroposterior axis of the early embryo, and which helps designate the main divisions of the insect body. (Figure 21–20) gap junction Communicating channel-forming cell–cell junction present in most animal tissues that allows ions and small molecules to pass from the cytoplasm of one cell to the cytoplasm of the next.
gastrulation Important stage in animal embryogenesis during which the embryo is transformed from a ball of cells to a structure with a gut (a gastrula).
gated transport   Movement of proteins between the cytosol and the nucleus through nuclear pore complexes in the nuclear envelope that function as selective gates.
geminin   Protein that prevents the formation of new prereplicative complexes during S phase and mitosis, thus ensuring that the chromosomes are replicated only once in each cell cycle.
gene Region of DNA that is transcribed as a single unit and carries information for a discrete hereditary characteristic, usually corresponding to (1) a single protein (or set of related proteins generated by variant post-transcriptional processing), or (2) a single RNA (or set of closely related RNAs).
gene control region The set of linked DNA sequences regulating expression of a particular gene. Includes promoter and cis-regulatory sequences required to initiate transcription of the gene and control the rate of transcription. (Figure 7–17) gene conversion   Process by which DNA sequence information can be transferred from one DNA helix (which remains unchanged) to another DNA helix whose sequence is altered. It often accompanies general recombination events. (Figure 5–59) gene family   The set of genes in an organism related in DNA sequence due to their derivation from the same ancestor.