Chromosomes

Chromosome Abnormalities Numerical abnormalities Structural abnormalities Mixoploidy

Numerical Abnormalities Monosomy Trisomy

A. B. C.

Non-disjunction

Consequence of non-disjunction Trisomy (21) Down syndrome (13) Patau syndrome (18) Edward’s syndrome

Polyploidy Addition of one or more entire set of chromosomes

Disorders of Chromosome Number Down Syndrome Patau and Edwards Syndrome Klinefelter Syndrome Turner Syndrome XXX Females and XYY Males

Down Syndrome

Down Syndrome History Incidence 1 in 691 births in the US 1866 first clinically described by Dr. Down 1959 chromosomal basis discovered Incidence 1 in 691 births in the US Majority of cases are diagnosed prenatally (~60%) Prevalence: currently 400,000 in US

Patau Syndrome

Patau Syndrome Heart defects Brain or spinal cord abnormalities Weak muscle tone Prognosis 45% die within few days/weeks 80% within 1st year

Edwards Syndromes

Edward’s syndrome Clinical symptoms Structural heart defects Intestinal abnormalities Breathing difficulties Intellectual disability Prognosis Median lifespan – 5-15 days Longer than 1 year – 8% Live to 10 years- 1%

Klinefelter Syndrome

Klinefelter Syndrome (XXY) Incidence- 1 in 1000 live male births Clinical features- Lower than normal verbal IQ Infertility Testosterone treatment

Turner’s Syndrome

Turner Syndrome (X) Incidence- 1 in 5000 – 10,000 female births Clinical features Loss of ovarian function Normal intelligence Developmental delay Learning disability Estrogen treatment from puberty on

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