Chromosomes

• Chromosomes are made from DNA which stands for deoxyribonucleic acid
• Genes are short sections of DNA that determine the characteristics of living things. There are 46 chromosomes in the human body arranged into 23 pairs - with the last of these, determining biological sex
• The chromosomal structure for females is XX and for males XY - so named because this is how the appear under a microscope
• All normal cells produced by a human ovary have an X chromosome. Half the sperm carry an X chromosome and half a Y chromosome
• A baby's sex is determines by the fertilising sperm
• The Y chromosome carries a gene called 'sex-determining region Y' or SRY for short.
• The SRY causes testes to develop in a XY embryo. These produce androgens: male sex hormones, which cause the embryo to become a male, without them the embryo develops into a female.
• From a 'purely' biological perspective gender and sex are one and the same - any differences between males and females are seen to be the result of anatomical, chromosomal and hormonal differences. From this perspective, 'anatomy is destiny' in the sense that our biological sex determines our gender identity and development
• Klinefelter's overview:

  affects approx. 1/750-1000 males

  individuals are biologically male, with the anatomical appearance of a male

  have an additional X chromosome (XXY)

  10% of cases identified by prenatal diagnosis

  thought that around 2/3 those affected not aware

  diagnosis often comes as a result of medical examination for unrelated condition
• Physical characteristics of Klinefelter's

  1. reduced body hair (frontal baldness)
  2. can have some breast development at puberty (gynecomastia)
  3. softening/rounding of body contours
  4. long gangly limbs
  5. underdeveloped genitals
  6. problems with co-ordination, clumsiness
  7. susceptible to health problems that are usually found in females e.g. breast cancer
  8. infertility
• Psychological characteristics of Klinefelter's:

  1. poorly developed language skills and reading ability
  2. individuals tend to be passive, shy and lack interest in sexual activity - feel inferior/anxious due to physical appearance
  3. many tend not to respond well to stressful situations
  4. Often exhibit problems with 'executive functions' such as memory and problem solving
• Turner's Syndrome overview:

  1. approx 1/2,200-5000
  2. biological females
  3. absence of one of the X chromosomes (X0)
  4. Have 45 chromosomes instead of 46
• Physical characteristics of Turner's

  1. no menstrual cycle (amenorrhoea) - ovaries fail to develop - infertile
  2. don't develop breasts at puberty - instead have a broad 'shield' chest
  3. low set ears
  4. webbed neck
  5. high waist-to-hip ratio (hips not much bigger than waist)
  6. tend to retain appearance of pre-pubescent girl
• Psychological characteristics of Turner's

  1. higher than average reading ability
  2. performance on spatial, visual memory and mathematical is lower than normal
  3. tend to be socially immature - trouble relating to peers and fitting in