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Chromosome Pairs in Human Cells

Online at http://cancerquest.emory.edu/index.cfm?page=648

The image below shows the chromosomes from a human cell. The depiction of all of the chromosomes in this manner is known as a karyotype. Karyotypes are often performed on fetal tissues during pregnancy to detect chromosomal abnormalities in the unborn child. These chromosomes have been colored by the binding of fluorescent dyes. Notice that there are two copies of each chromosome. The wide range in sizes of the chromosomes is also apparent. The chromosomes are numbered in the inverse order of their size. Chromosome 1 is the largest chromosome and the smallest chromosomes are those numbered 21 and 22. The karyotype shown below is from a male and contains one X and one (much smaller) Y chromosome. The DNA in even the smallest of the chromosomes contains millions of basepairs.