Chromosomes

Karyotype – the total chromosome constitution of an individual

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

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

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

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

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

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

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

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