And they will continue this replication and empowerment throughout the child s existence. Life as we know it is impossible without mitochondria. Yet all mitochondria are inherited from the mother and only from the mother. T he sexual form of an individual is determined by its sex chromosomes. Because of this, females are actually creatures of one X-chromosome.
Males are also creatures with only one X-chromosome.
The Y-chromosome is that which was added by evolutionary processes to create the male from the female. The first set of hormones stops the production of fully-formed female sexual characteristics. This is required because the functional X-chromosome of both males and females contains complete instructions for molding the fetus into a female, a process that will continue automatically if not interrupted. To produce a canonical male form, these genes must be switched off, by the chemical action of hormones, before the second surge of chemicals is allowed to arise. That second set of hormones sets in motion the production of male sexual characteristics.