1. Chromosomes & Karyotypes

2. Chromosomes

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

4. Chromosomes may fail to separate during meiosis
Nondisjunction
Chromosomes may fail to separate during meiosis
Resulting gametes may have too few or too many chromosomes

5. Disorders: Trisomy (an extra chromosome) Nondisjunction
Down Syndrome – three 21st chromosomes
Klinefelter’s Syndrome – XXY chromosomes
Edwards Syndrome three 18 chromosomes
Patau’s Syndrome three 13 chromosomes

6. Monosomy (one fewer chromosome) Turner Syndrome – single X chromosome
Nondisjunction
Disorders:
Monosomy (one fewer chromosome)
Turner Syndrome – single X chromosome

7. Normal Male
2n = 46

8. Normal Female
2n = 46

9. Male, Trisomy 21 (Down’s)
2n = 47

10. Female Down’s Syndrome

11. Klinefelter’s Syndrome

12. Turner’s Syndrome
2n = 45