Introduction to Genetic Analysis 603

Introduction to Genetic Analysis 603 - 44200_18_p575-610...

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18.8 The genetics of sex determination in humans An important part of development is the development of sex. Most animals and many plants show sexual di- morphism and, in most of these cases, sex determination is genetically “hardwired.” We will look at humans as an example, while noting that there is a range of deter- mination mechanisms quite different from that which follows. However, in human sex determination, we will see some developmental players that by now should be familiar—notably, a toggle switch, wide-acting transcrip- tion factors, and cell-to-cell communication. Follow this story by referring to Figure 18-33, which shows sexual development in men. It is clear that the key toggle switch is the gene on the short arm of the Y chromosome called SRY ( s ex r egulation on the Y ). The presence of SRY leads to maleness, whereas its absence leads to femaleness. Its importance is witnessed by the observation that if SRY is deleted or has null function, then an XY female results, and, conversely, if
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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