atypical sex chromosome

• Klinefelter's syndrome


  • Individuals have an additional X chromosome (XXY)
  • Leads to excess in oestrogen
  • Poorly developed language skills and reading ability, passive, shy and lack interest in sexual activity
• Turner's syndrome


  • Caused by an absence of one of the two allocated X chromosomes (X0)
  • Lack of oestrogen
  • No period, no breasts, low set ears and webbed neck, higher than average reading ability but lower spatial visual and mathematical abilities
• By comparing people who have chromosomal abnormalities to chromosome-typical individuals, it becomes possible to see psychological and behavioural differences between the two groups
• Klinefelter's syndrome


  Condition where males have the physical appearance of a male and have an additional X chromosome – their chromosome structure is XXY
• Klinefelter's syndrome effects


  Excess in oestrogen
• Effects of an extra chromosome on Klinefelter's syndrome

  • Physical: less body hair, breast tissue development, long limbs
  • Psychological: Poorly developed language skills and reading ability, Passive, shy and lack interest in sexual activity
• Turner's syndrome


  Caused by an absence of one of the two allocated X chromosomes - this is referred to as X0. Affected individuals have 45 chromosomes rather than the usual 46.
• Turner's syndrome effects


  Lack of oestrogen
• Characteristics of Turner's syndrome


  • Physical: no period, no breasts, low set ears and webbed neck
  • Psychological: higher than average reading ability, spatial visual and mathematical abilities lower, immature
• These differences have a biological basis and are a direct result of the abnormal chromosome structure
• The relationship between the chromosomal abnormalities associated with Klinefelter's syndrome and Turner's syndrome and the differences in behaviour seen in these individuals is not causal
• Environmental and social influences are more responsible for the behavioural differences seen in these individuals
• Continued research into atypical sex chromosomes patterns is likely to lead to earlier and more accurate diagnoses of Turner's and Klinefelter's syndromes as well as more positive outcomes in the future- treatments, eg oestrogen theraphy in TS, and testosterone therapy in KS treats symptoms (examples)
• An Australian study of 87 individuals with Klinefelter's syndrome showed that those who had been identified and treated from a very young age had significant benefits compared to those who had been diagnosed in adulthood
• Caution should always be executed when drawing conclusions from such an usual and unrepresentative sample of people
• Individuals who look different (because of their unusual chromosomes), are unlikely to be treated in the same way as their peers- therefore must consider environmental influence
• This may muddy the waters when trying to assess the relative contribution of nature and nurture in terms of behavioural and psychological differences
• Gender is in fact a social construct, and so what may be typical in the eyes of one person, for example in terms of social skills in the case of Turner's Syndrome, may be atypical in the eyes of another
• There is a lack of an objective method to measuring the utility of the contributions of these syndromes to the debate
• what chromosome is where the atypical chromosome is

  23rd pair