Gender Determination

During the sexual act the male ejaculation releases about 400 million sperm into the vagina. Many die and only a few thousand make it as far as the fallopian tube. Whilst many will try, only a single sperm will succeed in entering and fertilizing the egg.

From the moment of fertilization, a human embryo begins to form and after just 8 weeks all of the main organs are formed.

Every child receives 23 chromosomes from each parent and it is the 23rd set of chromosomes that determine gender and sex dependant on whether a "Y" or an "X" chromosone is received from their father.

Just as in all other stages of development, in 99% of cases nature gets it right, but just as an abnormality can occur in any other chromosome set leading to conditions such as a hole in the heart and many other conditions, so to the slightest problem in the 23rd set can create gender and sexual problems.

Transsexuals are born with a miss-match between their physical and brain sex and although there is still along way to go in understanding the full implications of chromosomes, it is thought to also influence sexual preferences etc.

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