1. Chromosomes

2. Karyotype – the total chromosome constitution of an individual

3. Normal Human Chromosome Numbers Homologous chromosomes – pairs of chromosomes Diploid – two sets of chromosomes, found in almost all cells Haploid – one set of chromosomes, found only in gametes – sperm or eggs Autosomes – pairs 1 – 22

4. Sex Chromosomes – pair 23 Female – two X chromosomes Male – one X and One Y If Y is present the individual is a male, and if no Y the individual is female Both males and females have at least one X

5. Abnormal Chromosome Numbers Monosomy – lack one of the homologous chromosome, can not survive development if lack autosome YO – not viable, important information is on the X chromosome, very little information is on the Y

6. Turner Syndrome – XO, only has one sex chromosome the X Short stature Underdeveloped sex organs Infertile

7. Trisomy – more than two copies of any pair of chromosomes Most examples of trisomy of the autosomes do not survive development Usually associated with chromosomes 13, 18 or 21

8. Down Syndrome – have extra 21 st chromosome Mental retardation Poor muscle tone Enlarged tongue Skin fold in corner of eye

9. Extra Sex Chromosomes Klinefelter Syndrome – XXY Male with underdeveloped male sex organs, may have some female body characteristics Tall, with long limbs Sterile

10. Trisomy X – three or more X’s Normal, healthy Fertile Jacob syndrome – XYY Taller than normal Once thought to be more aggressive, but proven wrong Fertile Some show mild mental impairment