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