How do scientists identify chromosomes? Additional, missing, or damaged chromosomes cause several human genetic disorders. One way of studying these disorders is to observe the chromosomes themselves.

Karyotyping – tool used to determine the sex of an individual or detect/identify chromosomal abnormalities

Karyotypes are treated with chemicals that stops cell division at the metaphase stage. During metaphase, the chromosomes are at the best/longest length for identification.

The cells are treated further, stained, and then placed on glass slides. The chromosomes are observed under the microscope and then photographed. Humans have 46 chromosomes in every diploid (2n) body cell. The chromosomes of a diploid cell occur in HOMOLOGOUS PAIRS, which are pairs of chromosomes that are similar in size, shape, and the position of their centromere. In humans, pairs 1-22 homologs are called AUTOSOMES. Pair 23 determines the individual’s sex so that pair is referred to as the SEX CHROMOSOMES.

Normal Female Karyotype (XX at pair 23)

Normal Male Karyotype (XY at pair 23)

AND NOWWWWW… I officially induct you as amateur genetic interns to help in identifying various human genetic disorders. Go to each assigned lab station and analyze the karyotypes. Let’s get started…

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