1. With regard to gender development
Today we are looking at the role of genes and hormones.

2. Key Question Is gender the product of Nature or Nurture
Are we born knowing we are male or female? Or Is our sense of maleness and femaleness the product of our upbringing?
Is gender the product of Nature or Nurture

3. Why are some people born male – but believe they are really female?
Why are some people born female – but believe they are really male?

4. We need to be able to explain the role of genes and hormones in gender development
We also need to be able to explain the role of upbringing and other environmental factors

5. Genes

6. A GENE contains a set of instructions. It is a carrier of information.
A gene consists of a long
strand of DNA
A chromosome is a double
chain of DNA
Every nucleus in every cell in the
body contains a set of 23
Chromosomes.
Genes sit on chromosomes

7. Each individual human has a genotype this is the genetic make up.
Each person has a phenotype which is what the individual becomes when their genes interact with each other and the environment.
I may have a genotype which indicates I will grow tall. However if I grow up without adequate nutrition this gene may never become my phenotype

8. Some genes always lead to certain characteristics; these are known as dominant genes – to produce a characteristic, a dominant genes need to be on only one of the pair of chromosomes.
Bb =
Some genes need more than one copy to produce a characteristic; these are known as recessive genes – if a recessive gene is present on only one of the pair of chromosomes, the characteristic will not appear.
Bb = bb =

10. However...
Recessive genes can be passed on and may appear in a future generation.
Such characteristics can be aspects of appearance, personality or behaviour

11. Examples of the effects of genes on humans
Some diseases and characteristics are sex linked – they are controlled by the sex genes. e.g. most colour blind people are men.

12. Environmental triggers on genes
Sometimes genes do not influence physical characteristics unless the ‘right’ environmental conditions occur.
These genes are known as epigenetic
Twin studies like Gottesman & shields suggest schizophrenia could be epigenetic

13. Sex chromosomes influence sex/gender development
The genetic blueprint for a person is organised into 23 pairs of chromosomes
22 pairs are both X shaped. The 23rd depends on whether the person is female or male
XX – female XY - male

14. Sex chromosomes

15. Chromosomes link to hormones
An embryo will always develop as a female unless instructed otherwise
The instructions to become ‘male’ are on the SRY gene found on the Y chromosome
The SRY gene on the Y chromosome contains instructions for the embryo to produce androgens (male sex hormones)
This causes the embryo to develop along the ‘male path’

16. Sexual development
At about 6 weeks gestation the GONADS or sex organs begin to develop but there is no difference between the developing sex organs of males and females at this stage.
The SRY gene in the Y chromosome produces a protein called ‘testis-determining factor’ which instructs the gonads to develop into testes rather than ovaries.
Once this has happened hormones take over….

17. HORMONES hormonal influences on sex/gender development
Read about this in your text book

18. There are a number of different hormones involved in sex development
H-Y antigen hormone – stop ovaries developing and starts testes development
Anti Mullerian Hormone –prevents the further development of female genitals
Hormones dictate gender differences and cause male and female brains to develop differently!!!!

19. The Male Brain - Joke!!

20. The Female Brain -Joke!!
Point is male and female brains are different

21. Sometimes Abnormal sex differentiation occurs
Problems with sex differentiation can occur at any time during development.
Problems can arise at fertilisation e.g. some boys have an extra chromosome XXY
This is known as Klinefelter’s syndrome.

22. Klinefelter’s syndrome

23. Klinefelter’s syndrome
Physical differences
Underdeveloped genitalia
Gynaecomastia
Poor language abilities,
learning difficulties
‘Shy and passive’ temperament

24. Girls with XO chromosomes have Turner’s syndrome

25. Turner’s syndrome Physical differences (neck, stature)
Underdeveloped ovaries, lack of menstruation at puberty
Poor spatial and mathematical abilities
Poor social adjustment

26. The Role of Hormones Like neurotransmitters, hormones carry messages
However, the messages are passed much more slowly because hormones travel in the bloodstream
They affect numerous
processes such as growth,
development, mood and
metabolism

27. Hormones are produced by endocrine glands, which include the pituitary, thyroid and adrenal glands
Hormones are also produced by males in the testes and females in the ovaries
The female hormones are oestrogen and progesterone
The male hormones are androgens such as testosterone
Hormones continue to affect sexual development throughout puberty…………

28. Gender development can also be affected by hormone problems
If the developing foetus does not respond to androgens the foetus will have neither male nor female internal duct structures.
A lack of the Mullerian (female) inhibiting substance together with androgen secretion can lead to a foetus having both male and female duct structures.
(see hand out )

30. Hormone differences can affect health and lifestyle throughout a person’s life.
For example – more females develop pain syndromes like fibromyalgia and they also tend to suffer more from mood disorders such as depression and anxiety.
On the other hand, more men than women are likely to develop alcoholism and to abuse drugs.

31. A great deal of research into hormones and gender development is conducted on animals!

32. Evaluation of biological explanations for gender development
The results of biological explanations are based on tests that can be repeated e.g. injecting rats with additional testosterone, or using MRI scanning in humans to detect blood flow. The results are replicable and can be shown to be reliable

33. Weakness
There is a problem with generalisability because many findings come from animal studies.
There are many differences between humans and animals, so some findings may not be as relevant to humans and may therefore lack credibility.

34. Now read p31 in your Bio pack
Think about Pseudo hermaphrodites like Daphne Went – this evidence refutes the genetic explanation of gender development. How?
Androgenital syndrome and Androgen sensitivity syndrome support the argument that pre-natal exposure to certain hormones determines gender development – This means hormone exposure can override genetic sex.
There is an argument that gender is a result of interaction between biology and environment. From the moment a child is conceived it is subject to influence from the environment…can you think of any examples?

35. 1. Complete the matching task on p33 of your bio packs
HW:
Use your text book to complete p25-29 in your Bio Pack