Chromosomes & Karyotypes

Chromosomes

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

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

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

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

Normal Male 2n = 46

Normal Female 2n = 46

Male, Trisomy 21 (Down’s) 2n = 47

Female Down’s Syndrome

Klinefelter’s Syndrome

Turner’s Syndrome 2n = 45