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Gl o ssa r y Accessory chromosome The term used by McClung to describe an unusual chromosome found in male, but not in female, grasshoppers. Acrosome A sac-like region of the sperm’s head, which contains proteins that recognize an egg surface, and enzymes that digest the covering region of the egg and permit fertilization. Alternation of generations The shift, in some plants, between a diploid generation (sporophyte) and a haploid generation (gametophyte). This is particularly striking in the mosses and liverworts. Androgen A male hormone, especially testosterone. Androgen insensitivity syndrome An X-linked mutation in XY embryos that form internal testes but, because their sexual embryonic tissue does not respond to testosterone, they have female pudenda and are raised as females. They lack a uterus and oviducts, and they have a short vagina. In older literature it was called testicular feminization syndrome. Now, it is designated 46,XY DSD with androgen insensitivity. Androgyny A neutral behavior with either a blend of masculine and feminine cultural behaviors, or an asexual approach to behavior. It is often associated with clothing and other cultural signs of sexual identity. 192 Glossary Aneuploidy The gain or loss of genetic material, usually one or more chromosomes in a cell, frequently leading to malformations or abortion in human embryos. Anti-Müllerian hormone The hormone produced by the Sertoli cells that leads to the destruction of the Müllerian ducts in male embryos. Abbreviated as AMH or MDI (for Müllerian Duct Inhibitor, its other name). ATRX gene In mammals an X-linked gene mutation that can cause a failure of XY embryos to form testes. Balance theory of sex determination In Bridges’s model for fruit flies, the ratio of X chromosomes to autosomes determines sex. It is 2X: 2A = 1.0 for females, 1X: 2A = 0.5 for male. Those aneuploid conditions between 1.0 and 0.5 are intersex as in 2X: 3A = 0.67. Note that a triploid 3X: 3A = 1.0, and they are fertile females. Blastocyst An embryonic structure consisting of an outer tissue and an inner mass of stem cells. The outer tissue is involved in implantation in the uterus. The stem cells produce the future embryonic body. Cell doctrine The belief that all cells arise from preexisting cells. Cell nucleus An organelle of the cell that has a porous outer nuclear envelope and which contains the chromosomes. Cell theory The universally found composition of all higher plants and animals whose organs and tissues are composed of microscopic cells. All higher plants and animals are communities of cells. Cholesterol A multi-ring compound synthesized in several tissues of the body that can be converted into steroid hormones or into vitamin D. Chromatin spot The inactivated X chromosome in mammalian females . It is usually located at the inner border of the nuclear envelope. It is also called sex chromatin or designated as chromatin positive when a cell is stained at interphase just before cell division begins. Chromosomal sex The designation of a cell as being XX or XY, the former usually female and the latter usually male. Glossary 193 Chromosome A thread-like structure composed of sequences of nucleotides that are chemically identified as genes. Chromosomes are linear in eukaryotic cells and have two tips, and a region somewhere along their length that is modified for attaching to fibers that move them during cell division. Chromosome number Each species has a specific chromosome number . For normal humans, the diploid number is 46. This is represented symbolically as 2N = 46. Compensasome The set of genes associated with dosage compensation in fruit flies. Also called a dosage compensation complex (DCC). Continuity of chromosomes The retention of the size and shape of each chromosome as it is copied, distributed, and ends up in two new cells. Corpus luteum The hormonal tissue formed from the discharged Graafian follicle. Its major hormone is progesterone, which permits implantation and the growth of the embryo. Cross-dresser Also called a transvestite in older terminology. It is applied to biological males who use clothing and other cultural attributes assigned to women. In females, it involves the adoption of clothing and other cultural attributes assigned to men. Crossing over A process during meiosis in which segments of chromosomes are exchanged between each pair of participating chromosomes. CYP21 A gene associated with 95% of female pseudohermaphrodites (XX or ovarian DSD CYP21 deficient). The condition involves an enzymatic step, 21-hydroxylase deficiency, that prevents cortisol formation . This, in turn, leads...


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