Atypical Sex chromosome patterns Flashcards
Klinefelter’s Syndrome (KS) is a genetic condition, which affects
1 in every 750 males and involves having an extra X chromosome (XXY)
Males with Klinefelter’s Syndrome have
small testes that produce insufficient amounts of testosterone before birth and during puberty, which results in normal male sexual characteristics not developing fully.
Klinefelter’s Syndrome
Physical effects:
Lack the 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.
Klinefelter’s Syndrome
Psychological effects:
Poor language skills, which affects reading ability;
A noticeably passive (quiet) temperament;
Attention problems;
An increased risk of anxiety disorders and depression.
Although a genetic condition, KS is not inherited
from parents. It occurs due to an error in cell division, which causes an egg or sperm cell to have an extra copy of the X chromosome.
This leads to the embryo produced at conception having an extra copy of the X chromosome in each of its body cells.
(P) There is research support for the relationship between atypical sex chromosome patterns and brain development.
E) DeLisi et al. (2005) subjected 11 KS participants and 11 non-KS controls to a psychiatric interview, cognitive tests and an MRI scan.
Ten of the KS males had some form of psychiatric disturbance and generally KS males had smaller frontal lobes, temporal lobes and superior temporal gyrus brain areas, which might explain the language deficits noted in the KS participants.
(C) This suggests a biological basis to the problems experienced by KS males.
(P) However, although the effects of KS originate directly from biological influences of genes and chromosomes, some effects are more environmental in nature.
(E) Stocholm et al. (2012): investigated criminal patterns in 1,005 Danish men and found that 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.
However, when adjustments were made for socioeconomic variables (level of education, fatherhood, cohabiting with a partner, etc.), conviction levels were similar to controls (apart from sexual abuse and arson).
(C) This 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 (TS) is a genetic condition that affects
~ 1 in 2,200 females and involves having only one complete X chromosome in each cell; the second X chromosome is either missing or incomplete (XO).
Turner’s syndrome
Physical effects
Short stature;
Down-slanting eyes;
Short, webbed-like neck;
Broad chest;
Lots of moles;
Organ abnormalities especially of the heart and kidneys
what is the main deficiency of Turner’s syndrome
The main deficiency is non-functioning ovaries, which results in girls with TS not developing breasts during puberty, not having periods and being infertile.
Turner’s syndrome
However,
~ 1/3 of girls with the condition have some typical changes during puberty
~ 1 in 200 with the condition can get pregnant naturally and most will have a normal vagina and uterus.
There are few psychological problems with TS…
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).
(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) Research into patients with TS has seen the development of therapies to improve the quality and duration of their lives.
(E) Quigley et al. (2014) gave 123 girls with TS either oestrogen supplements or a placebo from ages 5 to 12. There were no differences in physical development between the two groups before age 8.5 years, but 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.
(C) The findings suggest oestrogen supplements are beneficial between ages 8 and 12 and have a great psychosocial benefit in normalising breast development for girls with TS.
(P) Both KS and TS can be diagnosed prenatally based 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.
