Unformatted text preview: The number of chromosomes is the same as the number of centromeres. Before a cell enters mitosis or meiosis, the sister chromatid is synthesized. Left: one chromosome, with one chromatid. Right: same chromosome, after S phase, now with two chromatids (new sister chromatid shown in grey). Centromeres are shown as white circles. Human karyotypes are made from cells in late prophase or occasionally metaphase, so that the chromosomes are condensed and easy to see; also, both chromatids are present for each chromosome. Hence our typical representation of chromosomes as X-shaped. Image borrowed from: http://homepages.uel.ac.uk/V.K.Sieber/s olidktp.jpg To try making a karyotype yourself, go to this link: http://learn.genetics.utah.edu/units/disord ers/karyotype/karyotype.cfm...
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- Fall '08
- DNA, meiosis II, Sister chromatid, haploid chromosome number