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 21st 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