GEN-3020 Lecture Notes - Lecture 8: Blastocyst, X-Inactivation, Klinefelter Syndrome
8 Oct 2016
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Document Summary
Dissimilar or heteromorphic chromosomes (xy) characterize one sex or the other in a wide range of species. There are several different mechanisms of sex determination: Secondary sexual differentiation - involves overall appearance of organism (attraction) Some organisms spend their life cycle in the haploid phase. Plant life cycles alternate between the haploid gametophyte and diploid sporophyte stages. Diploid sporophyte stage predominates and both male/female structures are present on the adult plant. For example, the slipper limpet lives in stacks and changes sex depending on its position in the stack. Heterozygous turtles can be female during warm climates and male during cold (vice versa for alligators). Caenorhabditis elegans - nematode that has two sexual phenotypes; males have only testes and hermaphrodites have both testes and ovaries. Protenor mode is otherwise known as the xx/xo mode of sex determination. Lygaeus mode is the more common mode of sex determination: xx/xy. In humans, the male phenotype is the heterogametic (xy) sex.
