CHROMOSOMAL SYNDROMES

Human Chromosomes

Down’s Syndrome

Down’s Syndrome

•Caused by: extra copy of chromosome 21 (trisomy 21)

•Frequency: 1 in 700

•Symptoms: • short stature• heart defects• often sterile• some degree of intellectual disability

• Small ears• Slanted eyes

Patau Syndrome

Patau Syndrome

•Caused by: extra copy of chromosome 13 (trisomy 13)

•Frequency: 1 in 5,000

•Symptoms: • Brain, eye, circulatory defects

• Cleft palate• Kidney defects• Polydactyl (extra fingers/ toes)

• Structural eye defects

Edward’s syndrome

Edward’s Syndrome

•Caused by: extra copy of chromosome 18 (trisomy 18)

•Frequency: 1 in 10,000

•Symptoms: • Short life span (only a few months)

• Mental delay• Low birth weight• Defects in heart and other organs

• Overlapping fingers

CHROMOSOMAL SYNDROMES INVOLVING SEX CHROMOSOMES

Klinefelter syndrome

Klinefelter Syndrome

•Caused by: XXY

•Frequency: 1 in 500 to 1 in 1, 000males

•Symptoms: • Male sex organs• Sterile• Breast enlargement• Feminine body characteristics

• Normal intelligence

Jacob’s syndrome

Jacob’s Syndrome

•Caused by: XYY

•Frequency: 1 in 1, 000males

•Symptoms: • Taller than average• Often below normal intelligence

• It was thought that these men were more aggressive, but this hypothesis has been disproven over time.

Trisomy X Syndrome

•Caused by: XXX

•Frequency: 1 in 1, 000females

•Symptoms: • Healthy and fertile females

• Usually cannot be distinguished

Turner’s syndrome

Turner Syndrome

•Caused by: XO- missing

second sex chromosomes

•Frequency: 1 in 5,000females

•Symptoms: • Do not mature sexually

• Sterile• Short stature• Normal intelligence• 98% of fetuses die before birth