Sex Determination in mammals

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Sex Determination in mammals

Introduction

Mammals are large animals with long life cycles. They produce relatively few gametes and so use sexual reproduction to increase variation in order to adapt to environmental conditions with the maximum efficiency. As organisms have become larger and taken the form of the mammals we see today, a greater specialisation within each sex becomes an advantage; one member usually concentrating on producing energy-expensive eggs whilst the others produce large quantities of sperm. This process cumulates in the mammalian system of viviparity, when the embryo develops inside the female and the male will usually provide them both with food. With this increasing investment in young the potential dangers of inbreeding increase and the greater the need for mechanisms to insure outbreeding.

In this presentation we plan to highlight how the genes involved in the determination of the different sexes work to ensure that the highly conserved mechanisms for sexual reproduction are passed on to the progeny. This in turn facilitates the continuation of outbreeding necessary for natural selection.
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Genetic sex

The beginning of determination is from the inheritance of an X or Y chromosome from the father. If a Y chromosome is inherited then the progeny will be phenotypically male (XY), conversely, if an X chromosome is inherited the progeny will be phenotypically female (XX). These chromosomes contain the vital genetic information required for organogenesis of the sex organs. The genes involved can be seen below...

Genes and their role in primary sexual development

Name of gene

Location of expression

Role in sex determination

DAX1

In the genital ...

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