Normal Human Karyotype:   Karyotype are produced by staining and photographing the chromosomes as they divide. The pictures of the individual chromosomes are then cut out and paired up with their homologous pair.

The bands in the chromosomes can be seen after staining. This gives biologist another way match up the homologous pairs as well as size, shape and position of centromere.

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Errors in Meiosis: Nondisjunction

Some times there are errors in Meiosis. The resulting gamete can have too many or too few chromosomes. Most embryo that form with these errors naturally abort, but some survive.

Normal Karyotype	Abnormal Karyotype

Errors in the Sex chromosomes:

Some men produce serm that are O (with no sex chromosome), XX, YY, or XY instead of the normal X or Y. Woman can produce eggs with O or XX instead of the normal X.

Here some common abnormalies.

Carry out the Karyotyping activity. Log onto this website and carry out activity http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html

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Turner Syndrome

1:5000 female babies fail to menstruate or develop normal secondary sexual characteristics. They are sterile, usually short in stature and can have folds of skin around their necks.

Trisomy X (XXX)

1:1000 woman have three X chromosomes. No detectable defects, ecept for a higher incidence of below-normal inteligence. They are fertile and usually have normal children.

Klinefelter Syndrome (XXY)

1:1000 males at puberty develop mixed secondary sexual characteristics, including partial breast development, broadening of the hips, and small testes. They are sterile, usually increased incidence of mental deficiency.

XYY Males

1:1000 males. Below-normal inteligence and above average height. (some debate on whether they are more violent than normal males)

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Key terms:

Basic facts: http://homepages.ius.edu/GKIRCHNE/biomolec.htm