This lens offers a quick introduction to the determiation of gender. As will be seen, it's a very complex subject. To keep the subjet understandable by anybody, I have avoided being too technical in the text I have written; but I have included some Wikipedia articles for those who wish to take the subject further. The Wikipedia articles on this subject are of a good quality, although the situation is even more complex than the Wikipedia articles suggest.
For anybody looking for a detailed explanation of intersex conditions, I apologise. This isn't the lens to cover that in detail. I have written one specialist lens about Klinefelter's Syndrome so far, and am more.
For anybody looking for a detailed explanation of intersex conditions, I apologise. This isn't the lens to cover that in detail. I have written one specialist lens about Klinefelter's Syndrome so far, and am more.
Physical Indicators
Secondary Sexual Characteristics
Secondary sexual characteristics develop during puberty as a result of the action of the main sex hormones testosterone (male) and estrogen (female). Women develop breasts and subcutaneous fat giving them a curvy look; men's voices drop and their grow a beard. In practice they are just the most prominent changes and there is a wide range of changes brought on by the action of the main sex hormones.
Secondary sexual characteristics are a very weak way of determining gender. If a woman takes testosterone her voice will break and she will grow a beard and if a man takes estrogen (predominently estradiol) he will grow breasts. For this, and other reasons, secondary sexual characteristics like breards and breasts, while what people notice first, are not reliable indicators of gender.
Secondary sexual characteristics are a very weak way of determining gender. If a woman takes testosterone her voice will break and she will grow a beard and if a man takes estrogen (predominently estradiol) he will grow breasts. For this, and other reasons, secondary sexual characteristics like breards and breasts, while what people notice first, are not reliable indicators of gender.
Primary Sexual Characteristics
Certain gendered attributes are present before puberty. These are the primary sexual characteristics. There are some skeletal differences between men and women - particularly in the pelvis to ensure that the birth canal is obstructed when an woman gives birth - but the biggest difference is the reporoductive system.
Hermaphrodism & Physical Intersex Conditions
While it might be thought that presence of a male reproductive system defines and man and a female reproductive system a woman, it's not that easy. Some individuals may be born with aspects of both male and female reproductive system, a condition which used to be known as hermaphrodism but which these days is more commonly referred to as a physical intersex condition.
Hormones and Gender
Testosterone and Estradiol (Estrogen)
This video gives a very quick recap on the hormonal systems of men and women and the action of puberty.
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Testosterone
The video gives only a very basic introduction, for further information about the main male sex hormone testosterone, the Wikipedia article is a good place to start.It is produced in a number of ways, but in men the main factory for testosterone is the testes.
Genetics and Gender
Genetics Primer
It's common to refer to males as genetically XY and females as XX. This refers to variation between the two genders in chromosome 23 of human DNA. Before we look at variations with the basics of genetic sex determination, if you aren't familar, or your knowledge is rusty, then you might want to use one of these genetics primers as a refresher. (If you are studying genetics from scratch, it links to a second lens which has some tutorial videos to help explain the fundamentals.)
The two lenses are broadly similar so choose either male XX or female XY according to your interest.
The two lenses are broadly similar so choose either male XX or female XY according to your interest.
Androgen Insensitivity Syndrome and Gender
It might be thought that those who have a 46,XY karyotype are men and those with a 46,XX karyotype are women. It's not that straightforward.
Certain women have an insensitivity to androgens - to male hormones. That is, male hormones don't have their usual effect. Women who have a genetic condition known as Androgen Insensitivity Syndrome, AIS. These women have 46,XY karyotype but develop as women with normal female primary and secondary sexual characteristics (although they may not develop ovaries).
You can find out more by reading my page on this topic.
Certain women have an insensitivity to androgens - to male hormones. That is, male hormones don't have their usual effect. Women who have a genetic condition known as Androgen Insensitivity Syndrome, AIS. These women have 46,XY karyotype but develop as women with normal female primary and secondary sexual characteristics (although they may not develop ovaries).
You can find out more by reading my page on this topic.
Other Genetic Intersex Conditions
The situation is even more complicated then AIS would suggest. Some individuals may have a karyoype other than 46,XX or 46,XY. They for instance have an extra chromosome, such as 47,XXY. Other intersex conditions are even more complex and may for instance involve a mix of different karyotpes. This is referred to as mosaicism.
No Reliable Gender Test
As we have seen, there are exceptions to all of the obvious ways of differerentiating between men and women. While testing gender may at first sight seem an easy thing to do, it is in fact very difficult and in many cases science has not yet produced a definitive test for gender.
About Kate Phizackerley
(Introducing your lensmistress)
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by Kate-Phizackerley
Off Squidoo I am a middle-aged woman with a wide range of interests from Ancient Egypt, backgammon, cookery ... to ... Zimbabwe which I visited 20 years... more »
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