JAMES KING-HOLMES / ICRF / SCIENCE PHOTO LIBRARY JAMES KING-HOLMES / ICRF / SCIENCE PHOTO LIBRARY
Cytogeneticist analysing a karyotype of human chromosomes for diagnostic purposes. The paired chromosomes facilitate detection of abnormalities of number or structure, which may give rise to defects in the individual (such as Down's Syndrome and some leukaemias). A karyotype is a document of the full complement of chromosomes in a cell, arranged in numbered homologous pairs. The chromosomes are stained and photographed through a light microscope during the metaphase stage of cell division. Each member of a homologous pair (apart from the sex chromosomes in the male) is similar in length & banding pattern.
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