Topic Summaries

The role of chromosomes and hormones

A-Level > Psychology > AQA > A-Level Psychology Topic Summaries > Gender > The role of chromosomes and hormones
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Addiction

  • Chromosomes: strands of DNA containing many genes. These genes code for proteins and hormones.
  • After fertilisation, the sperm and egg nuclei fuse to form a diploid cell, meaning it contains 46 chromosomes (a full set), arranged in 23 pairs.The genotype for females is XX and for males is XY. The Y chromosome is important as it differentiates whether the baby will be a male or a female.
  • The Y chromosome triggers the activation of the SRY gene which triggers the production of androgens and directs the development of the testes which produce testosterone, an androgen (male hormone) that stimulates the production of male reproductive organs. High levels of testosterone are highly associated with higher levels of aggression. This is an evolutionary explanation. Higher levels of aggression have helped men retain their mates in the wild, which allowed their genes to be reproduced.
  • Oestrogen is the female sex hormone. It triggers the development of the female reproductive system (ovaries, fallopian tubes, and vagina). Fluctuations in oestrogen (alongside progesterone) are associated with premenstrual symptoms, including mood changes.
  • Women have higher levels of oxytocin than men. It is described as the ‘love hormone’ as it provides feelings of closeness and comfort. This may explain the stereotype that women are more caring than men. Oxytocin is also an evolved characteristic. Before and after birth, high concentrations of oxytocin are released into the mother’s blood which facilitates bonding and stimulates uterine contractions and milk release.
  • Having atypical sex chromosome patterns can cause Klinefelter’s syndrome in males and Turner’s syndrome in females.
    • Klinefelter syndrome is characterised by the genotype XXY and affects those who are biological males. People with this syndrome develop facial and physical features that are similar to females (e.g.softer faces) and gynecomastia (development of breasts which can lead to risk of breast cancer). Psychologically, people with this are more clumsy and score below average on tests of visuo-spatial and reading skills.
    • Turner’s syndrome is when biological females only have one X chromosome instead of two. This means they only have 45 chromosomes and a genotype of X0. Females with this condition typically have short stature, underdeveloped secondary sexual characteristics, infertility, and no ovaries so do not have a menstrual cycle. Psychologically, people with Turner’s have advanced reading skills but find social communication more challenging.

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