gamont the haploid adult form of those protoctists that have both haploid and diploid phases in their life cycles. Gamonts function in sexual reproduc- tion; they undergo gametogony to produce diploid agamonts. Meiosis takes place in agamonts, and the haploid agametes that result disperse, undergo mi- totic divisions, and differentiate into gamonts, com- pleting the cycle. gamontogamy the aggregation of gamonts during sexual reproduction and the fusion of gamont nuclei to produce agamonts. ganglion a small nervous-tissue mass containing numerous cell bodies. ganglioside a family of complex lipids containing sphingosine, fatty acids, carbohydrates, and neura- minic acid. The Gm2 ganglioside that accumulates in the brain of patients with Tay-Sachs disease (q.v.) is shown below. See Appendix C, 1935, Klenk. gap the position where one or more nucleotides are missing in a double-stranded polynucleotide con- taining one broken chain.
gap genes a class of Drosophila genes that control embryogenesis. Loss of function mutations result in the loss of contiguous body segments, and therefore gaps appear in the normal pattern of segmented structures in the embryo. See zygotic segmentation mutants. gargoylism a term covering two genetically dis- tinct hereditary diseases of connective tissue in hu- mans, Hunter syndrome (q.v.) and Hurler syndrome (q.v.). Garrod disease See alkaptonuria. gas chromatography a chromatographic technique in which an inert gas is used to sweep through a col- umn the vapors of the materials to be separated.