1. Chromosomes & Karyotypes
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2. Chromosomes
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3. Chromosome Number
All cells in the human body (SOMATIC CELLS) have 46 or 23 pairs of chromosomes
Called the DIPLOID or 2n number
GAMETES (eggs & sperm) have only 23 chromosomes
Called the MONOPLOID or 1n number
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4. Nondisjunction Chromosomes may fail to separate during meiosis
Resulting gametes may have too few or too many chromosomes
Disorders:
Down Syndrome – three 21st chromosomes
Turner Syndrome – single X chromosome (#23)
Klinefelter’s Syndrome – XXY chromosomes (#23)
Chi-du-chat – Affects chromosome #5
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5. Normal Male
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2n = 46

6. Normal Female
2n = 46
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7. Male, Trisomy 21 (Down’s)
2n = 47
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8. Female Down’s Syndrome
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9. Klinefelter’s Syndrome
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10. Turner’s Syndrome
2n = 45
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11. Cri-du-chat Syndrome
Cri-du-chat is caused by a deletion (the length of which may vary) on the short arm of chromosome 5. Multiple genes are missing as a result of this deletion, and each may contribute to the symptoms of the disorder.

12. Cri-du-chat syndrome

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