atypical - sex chromosome patterns

• Klinefelter's syndrome


  Genetic condition affecting 1 in every 750 males, involving an extra X chromosome (XXY)
• Klinefelter's syndrome


  • Small testes that produce insufficient testosterone before birth and during puberty
  • Normal male sexual characteristics not developing fully
  • Lack ability to grow facial and pubic hair
  • Have broader hips
  • Develop breast tissue
  • Have low muscularity and low fertility levels
  • Tend to have long legs and arms in ratio to their torso
• Psychological effects of Klinefelter's syndrome

  • Poor language skills, affecting reading ability
  • Noticeably passive (quiet) temperament
  • Attention problems
  • Increased risk of anxiety disorders and depression
• Klinefelter's syndrome is not inherited from parents, it occurs due to an error in cell division causing an extra copy of the X chromosome
• There is research support for the relationship between atypical sex chromosome patterns and brain development 11 KS participants and had 11 non-KS controls to a psychiatric interview, cognitive tests and an MRI scan. KS males had smaller frontal lobes, temporal lobes and superior temporal gyrus brain areas, which might explain the language deficits.

  Ten of the KS males had some form of psychiatric disturbance

  This suggests a biological basis to the problems experienced by KS males.
• Although the effects of KS originate directly from biological influences, some effects are more environmental


  Danish Men with KS had higher conviction rates for sexual abuse, burglary and arson, and lower conviction rates for traffic and drug offences than non-KS controls, but when adjusting for socioeconomic variables (education levels), conviction levels were similar to controls. suggests that KS is associated with increased criminality but as a result of poor socioeconomic conditions endured by sufferers rather than the condition itself.
• Turner's syndrome


  Genetic condition affecting 1 in 2,200 females, involving having only one complete X chromosome (XO)
• Physical effects of Turner's syndrome

  • Short stature
  • Down-slanting eyes
  • Short, webbed-like neck
  • Broad chest
  • Lots of moles
  • Organ abnormalities especially of the heart and kidneys
• Main deficiency in Turner's syndrome

  Non-functioning ovaries, resulting in girls not developing breasts during puberty, not having periods and being infertile
• About 1/3 of girls with Turner's syndrome have some typical changes during puberty, and about 1 in 200 can get pregnant naturally
• Psychological effects of Turner's syndrome

  • Potential problems with social adjustment due to physical appearance (e.g. possible bullying)
  • Potentially minor learning difficulties (some girls may have advanced reading ability though)
• Quigley et al. (2014)


  • Gave 123 girls with TS either oestrogen supplements or a placebo from ages 5 to 12
  • No differences in physical development between the two groups before age 8.5 years
  • Between 8.5 and 12 years those given oestrogen had earlier and greater breast development compared with those given a placebo, though no other differences in puberty developments were noted
• (P) There is research support for the relationship between atypical sex chromosome patterns and brain development.

  (E) Brown et al. (2002) performed MRI scans of 26 girls with TS and 26 gender- and age-matched non-TS girls, finding that girls with TS had smaller posterior cerebral and cerebellar brain areas. 

  There were no differences between TS girls who had a maternally inherited or a paternally inherited X chromosome.

  (C) This suggests that TS affects growth of certain brain areas, which may in turn be related to the developmental effects seen with the disorder. 
• (P) Both KS and TS can be diagnosed prenatallybased on cytogenetic analysis of a foetus.

  (E) However, this can be regarded ethically as a socially sensitive area, as such a diagnosis may incur a demand for or bring pressure upon prospective parents to ask for an abortion.