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

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

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

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

Genes

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

Definition Genes are units of information that are inherited from our parents. They control, or influence characteristics such as risk of mental health disorders, personality and sexual development. Genes are sections of strands of a chemical called DNA found in our cells.

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

Some genes always lead to certain characteristics; these are known as dominant genes – to produce a characteristic, a dominant gene 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 =

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

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.

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

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

Sex chromosomes

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’

Sex = when referring to the biological aspects of males and females Sexual development Sex = when referring to the biological aspects of males and females 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…. STOP

Tasks to recap genes and sexual development Using text books and your new knowledge, complete pgs. 25 & 26 in your packs If you finish this, please read ahead in your text books – hormones!

hormonal influences on sex/gender development Lesson 2 HORMONES hormonal influences on sex/gender development Read about this in your text book essentially they carry messages and can affcet mood, growth, development and metabolism

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!!!! - what differences do you think we have?!

The Male Brain - Joke!!

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

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.

Klinefelter’s syndrome

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

XYY syndrome

Characteristics an autism diagnosis an inability to grow facial or body hair attention difficulties delayed motor skill development, such as writing delayed or difficult speech delayed or absent puberty emotional or behavioural issues gynecomastia, or enlarged breast tissue hand trembling or involuntary muscle movements hypogonadism, or low testosterone levels hypotonia, or weak muscle tone learning disabilities low energy levels small penis small, undersized testicles taller than average height weak bones

Girls with XO chromosomes have Turner’s syndrome

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

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

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…………

Definition A Hormone is a chemical which is released from a gland, travels in the blood and affects target organs such as muscles, sex organs or other glands. For example sex hormones, such as oestrogen and testosterone are released by the gonads (sex organs). Oestrogen is produced by the ovaries in sexually mature females and testosterone is produced by the testes in sexually mature males (although a little of each is produced by both sexes). These hormones are responsible for many of the changes that occur around puberty such as the deepening of the voice in males and the onset of menstruation in females.

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 )

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.

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

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?

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

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