lecture 8- sex chromosome disorders

What are numerical sex chromosome abnormalities?

• deletion- part of a sex chromosome is missing

• Monosomy- one whole chromosome is missing

• Trisomy- an additional sex chromosome

  • Can be more e.g. tetrasomy

What is Turner syndrome?

• female genetic disorder

• Affects 1 in 2000 female babies, random occurence

• Have one X chromosome rather than 2 (XX)

• 2 types:

  • Classic- other X is completely missing

  • Mosaic- other X is somewhat missing or incomplete

• Sometimes diagnosed before birth using amniocentesis- amniotic fluid in uterus is extracted and tested

• Usually diagnosed in childhood/puberty using blood test.

• Symptoms: short, low birth weight, webbing, downward slanting eyes, broad chest with widely spaced nipples, increased risk of heart conditions, kidney abnormalities.

What is Turner syndrome like throughout life?

• childhood

  • Babies grow at normal rate until age 3- start to slow down

  • Some have learning difficulties e.g. social intelligence, spatial awareness, numeracy, attention, hyperactivity

  • May display impulsivity, over-activity, short attention span.

• Adolescence

  • During puberty, do not produce enough sex hormones (oestrogen and progesterone)

  • May not begin/complete sexual development, may not start ovulating

  • Vagina and womb develop normally

• Adulthood

  • Ovarian failure: infertility, early menopause

  • IVF most common options for infertility- rates of success are same.

  • Life expectancy reduced up to 13 years.

What is the psychological impact of TS?

• anxiety and depression

• Adhd

• Autism

• Self-esteem

• Social participation

• Lower social, psychological and physical quality of life.

What are the treatments for TS?

• specialists- endocrinologist (hormonal issues), psychologist (developmental), gynaecologist

• Growth- growth hormones therapy. Daily injection for approx 10 years, starting around age 5/6 for average increase of 5cm.

• Oestrogen and progesterone therapy- trigger pubertal development

• IVF

What is Klinefelter syndrome?

• male genetic disorder

• Affects about 1 in every 660 males

• Extra X chromosome on either gamete, resulting in XXY

• Extra chromosome carries copies of genes, interfering with development of testicles, leading to less testosterone produced

• Associated with increased maternal age.

• Often only discovered during investigations for infertility in later life. E.g. blood tests for hormone levels and presence of extra X.

• Symptoms: taller than average, long slender limbs, pear shaped hips, female fat distribution, breast development, scant body and facial hair, small testes and penis, infertility.

What is Klinefelter syndrome like throughout life?

• childhood

  • Babies learn to sit, crawl, walk, talk later than typical. And tend to be quieter and more passive.

  • Shyness in childhood and low self-confidence.

  • Problems reading, writing, spelling. Can have mild dyslexia/dispraxia

  • May have difficulties paying attention, socialising, expressing feelings

• Adolescence

  • Grow taller, long limbs

  • Feminine characteristics

• Adulthood

  • Low sex drive

  • Increased risk of: type 2 diabetes, osteoporosis, cardiovascular disease, blood clots, autoimmune disorders, hypothyroidism.

What are the treatments for Klinefelter syndrome?

• testosterone replacement therapy taken in form of gels or tablets in teenagers, or injections.

• Speech therapy during childhood

• Educational and behavioural support for learning difficulties

• Physiotherapy to build muscle/increase strength

• Artificial insemination using donor sperm or intracytoplasmic sperm injection (sperm removed in small operation)

• Breast reduction surgery.