50.1 MB (712.9 KB compressed)
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31.2 x 40.1 cm ⏐ 12.3 x 15.8 in (300dpi)
HERVE CONGE, ISM / SCIENCE PHOTO LIBRARY HERVE CONGE, ISM / SCIENCE PHOTO LIBRARY
Female Down's syndrome karyotype. The complete set of chromosomes of an organism is known as the karyotype. Humans usually have 46 chromosomes in total, arranged into 23 pairs. Down's syndrome, also called trisomy 21, is caused by the presence of three copies of chromosome 21 (bottom left). Down's syndrome results in mental retardation and flattened facial features. The XX chromosome pair at centre right indicates that this person is female. Males have an XY chromosome pair instead (the empty space for a Y chromosome is at bottom right).
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