Gender- Biological influences

Biological influences on Gender

Genes, Hormones and Evolutionary explanations

Definitions:

Sex: Refers to the biological facts about us, state of your sex chromosomes

Gender: Is what culture makes us, it is our sexual identity.

Genes

Typical sex chromosome patterns are ** for a female and XY for a male. The Y chromosome carries very little genetic material. There is usually a direct link between chromosomal sex and gonads (vagina/womb, penis/testicles).

However there are some exceptions for example the Bastia family, 4 children in the family were born with normal female genetelia but at puberty male genetelia appeared. They were genetically XY but had not developed male genetelia, because of insensitivity to the male hormone testosterone. During puberty massive amounts of testosterone are produced and this caused the male genetelia to appear. The girls seemed to accept their change of sex without difficulty. It was found that all families who had this problem had a common ancestor who passed on a mutant gene that shows only when carried by both parents.

Klinfelters syndrome- where males are born with **Y sex chromosomes, they have an extra X chromosome. Males with this chromosome are sterile and tend to be less muscular and have less facial hair and body hair. They can also have problems using language to express themselves and may have trouble with social interaction.

Hormones

The major male and female hormones are androgens and oestrogens. Both types of hormones are present in males and females but in very different amounts.

Chromosomes determine a person’s sex, but most sexual activity is governed by hormones. During parental development all embryos start developing in the same genital structure, and then male hormones such as testosterone cause the female parts to be absorbed and the male parts to develop. However even though testosterone may not affect the development of genetelia it may have significant masculinising effect on the developing brain in the foetus. For example testosterone promotes development in areas of the brain associated with spatial and mathematical skills, whereas oestrogen is though to do the same in the areas of the brain associated with verbal ability.

Men produce more testosterone (an androgen) each day then females, and females produce more oestrogens then males. However some humans produce smaller or larger quantities of these hormones then normal. For example sometimes more people are born with more testosterone than normal which is a particular type of syndrome called CAH.

-          This form of CAH can cause early sexual development in males, but doesn’t have much of an effect otherwise.

-          The behaviour of girls with this type of CAH tends to be masculinised as they enjoy tomboyish activities.

-          Physically girls tend to look more masculine their growth is fast and puberty can happen early.

-          CAH can also cause physical abnormalities such as ambiguous genitalia. This can make it difficult to tell if someone is male or female at birth.  

Research evidence

1.       Dorner (1974)

Injected female rats with…