Biological Factors Influencing Gender – Chromosomes and Hormones
The Role of Chromosomes and Hormones in Gender Behaviour
1. At conception, an egg is fertilised with a sperm. The egg always carries an X
chromosome, and it is the sperm that determines whether the foetus becomes male or
female. If the sperm carries an X chromosome, the foetus will become female (XX) and if
the sperm carries a Y chromosome, the foetus will become male (XY)
2. At about 6 weeks after conception, these chromosomes influence the development of
gonads. The male gonads are called testes and the female gonads are called ovaries. The
gonads are sex glands
3. At about 8 weeks, these gonads begin to produce hormones. If a foetus has a Y
chromosome and has developed testes, the testes begin to secrete the hormone
testosterone. This continues between 8 and 24 weeks. However, the ovaries produce
very few hormones before birth
Our late gender development in influenced by this hormone and two others:
Testosterone Impact Oestrogen’s Impact Oxytocin’s Impact
For the first six months after Oestrogen is involved in a Oxytocin is…
birth…Testosterone is number of different A polypeptide hormone
higher in boys than girls functions (physical and which acts also as a
behavioural), such as: neurotransmitter that
This influences male brains Development of breasts controls key aspects of the
to develop differently. For reproductive system
example… Premenstrual tension
There are differences in the (PMT) Its influence is stronger in
hypothalamus – the sexual females because it
dimorphic nucleus bigger in Onset of menopause combines with oestrogen to
males enhance its effects.
Oestrogen also has a role in For example:
feminising the brain… Facilitate childbirth (by
Promotes neural helping to stimulate
It also makes males show interconnections for a more contractions)
typically masculine ‘distributed’ female brain
behaviours such as… (equal use of both Facilitate breastfeeding
Competitiveness hemispheres) (by stimulating the ‘let
Aggressiveness down’ reflex)
Oestrogen is also associated
with typically feminine Increases five-fold
behaviours such as… during sex
Sensitivity
Co-operation Social behaviour e.g.
protect of offspring
It is important to note that all males and females have some level of all three of these
The Role of Chromosomes and Hormones in Gender Behaviour
1. At conception, an egg is fertilised with a sperm. The egg always carries an X
chromosome, and it is the sperm that determines whether the foetus becomes male or
female. If the sperm carries an X chromosome, the foetus will become female (XX) and if
the sperm carries a Y chromosome, the foetus will become male (XY)
2. At about 6 weeks after conception, these chromosomes influence the development of
gonads. The male gonads are called testes and the female gonads are called ovaries. The
gonads are sex glands
3. At about 8 weeks, these gonads begin to produce hormones. If a foetus has a Y
chromosome and has developed testes, the testes begin to secrete the hormone
testosterone. This continues between 8 and 24 weeks. However, the ovaries produce
very few hormones before birth
Our late gender development in influenced by this hormone and two others:
Testosterone Impact Oestrogen’s Impact Oxytocin’s Impact
For the first six months after Oestrogen is involved in a Oxytocin is…
birth…Testosterone is number of different A polypeptide hormone
higher in boys than girls functions (physical and which acts also as a
behavioural), such as: neurotransmitter that
This influences male brains Development of breasts controls key aspects of the
to develop differently. For reproductive system
example… Premenstrual tension
There are differences in the (PMT) Its influence is stronger in
hypothalamus – the sexual females because it
dimorphic nucleus bigger in Onset of menopause combines with oestrogen to
males enhance its effects.
Oestrogen also has a role in For example:
feminising the brain… Facilitate childbirth (by
Promotes neural helping to stimulate
It also makes males show interconnections for a more contractions)
typically masculine ‘distributed’ female brain
behaviours such as… (equal use of both Facilitate breastfeeding
Competitiveness hemispheres) (by stimulating the ‘let
Aggressiveness down’ reflex)
Oestrogen is also associated
with typically feminine Increases five-fold
behaviours such as… during sex
Sensitivity
Co-operation Social behaviour e.g.
protect of offspring
It is important to note that all males and females have some level of all three of these
