Biological Sex
Psychology: AQA A Level, topic 10.1.1
Biological Sex
Biological psychology states that biological sex differences between males and females are the result of sex chromosomes and sex hormones.
Decoupling of sex and gender
- Sex and gender are distinct concepts.
- Sex refers to the biological status of being male, female, or intersex, according to the APA Dictionary.
- Gender refers to the psychological, social, and behavioural aspects of being masculine, feminine, or non-binary.
- Recognising the decoupling helps avoid confusion between physical sex differences and gender identity or roles.
Chromosome patterns
- Humans are born with 23 pairs of chromosomes.
- 22 of these pairs are called autosomes. These are chromosomes that look the same in both males and females.
- The final 23rd pair of chromosomes are what determine sex.
- Males and females have different chromosome patterns:
- Males have a single X and a single Y chromosome.
- Females have two X chromosomes.
Chromosomes and reproduction
- A female will have two X chromosomes (XX).
- Therefore, when the female is producing eggs (ova), every ovum will contain an X chromosome.
- Males will have an X chromosome and a Y chromosome (XY).
- The Y chromosome determines that the child will be male.
Sperm and biological sex
- Each sperm cell contains an X chromosome or a Y chromosome.
- The sperm will determine the sex of the child.
- If the sperm has an X chromosome, when it combines with the egg (X), a female child will result (XX). If the sperm contains a Y chromosome, the child will be male (XY)
Genetic material
- A sperm cell contains one half of the genetic material (22 autosomes plus 1 sex chromosome), while the egg cell contains the other half (22 autosomes plus 1 sex chromosome).
- When the sperm fertilises the egg, the developing embryo will have a full set of genetic information (23 pairs or 46 chromosomes).
Atypical Sex Chromosome Patterns
Typically, males have an XY chromosome pattern and females have an XX pattern. Some individuals are born with variation to these patterns.
Klinefelter’s syndrome
- Klinefelter’s syndrome is when a person assigned male at birth is born with an extra X chromosome (XXY).
- This results in the male being taller, less muscular, and having less body and facial hair.
- Such persons are generally incapable of producing sperm, therefore are infertile.
Klinefelter’s syndrome cont.
- Such persons can also develop certain health complications like breast cancer or osteoporosis.
- The individuals can also have language deficits as they have difficulty expressing themselves and can have trouble with social interaction.
- Hormonal treatment of testosterone therapy can aid puberty and masculinization.
Turner’s syndrome
- Turner’s syndrome is when a person assigned female at birth is born without a second X chromosome (X), only having a single X chromosome.
- This results are the female being shorter, dysfunctional ovaries, and having abnormal puberty.
- Consequently, such persons are sterile.
- Generally, for such persons to be able to go through puberty, they receive hormonal treatments- oestrogen therapy.
Turner’s syndrome cont.
- Persons with Turner's syndrome can also have heart defects, skeletal abnormalities and kidney problems.
- Persons with Turner's syndrome to have poorer spatial ability and tend to do worse at maths.
Androgen Insensitivity syndrome
- Persons with Androgen Insensitivity Syndrome (AIS) have XY chromosome but the body cells do not respond to testosterone.
- Physical effects include external female characteristics despite XY chromosomes.
- Reproductive effects include absence of functional male genitalia and infertile.
- AIS highlights the role of hormones in developing physical sex independently of chromosomes.
- Two types of AIS are: complete (CAIS) and partial (PAIS).
Brain function and sex chromosomes
- By studying people with atypical sex chromosome patterns, researchers can learn what abilities may be due to sex chromosomes.
- If a variation in sex chromosomes causes an effect on brain function or behaviour, they could be explained by differing sex chromosomes.
Test yourself on Biological Sex
Sex and reproduction
What determines the sex of a baby?
How many pairs of chromosomes do humans typically have?
Which of the following is true about Androgen Insensitivity Syndrome (AIS)?