The Upright Ape: A New Origin of the Species

by Aaron G. Filler, MD, PhD

Figure 4-2 Mitosis and Meiosis

Meiosis and Mitosis

Figure 4-2 – Chromosomes in Mitosis and Meiosis

A – In standard cell division throughout the body (mitosis), each new cell receives an identical copy of the genetic information. A chromosome is a tightly coiled package containing a very long DNA molecule wrapped up in chromatin proteins. Each chromosome is present in two similar copies in each cell. B – The process of making gametes (DNA in sperm and egg) is different because it (meiosis) allows for the creation of unique new chromosomes and because the gametes have only a single copy of the chromosome. As in mitosis, the DNA is first replicated and the sister chromatids are joined at their centromere to look like an X. However, now the “homologous” pair members must find each other and line up – (this is the process that is disrupted in a chromosomal speciation event). There are then two rounds of splitting, Meiosis I and Meiosis II to produce the gamete.

Figure credit -

Modified, redrawn: -Reproduced with permission from the Office of Science Policy, the National Institutes of Health, the National Center for Biotechnology Information, and the National Library of Medicine, http://www.ncbi.nlm.nih.gov/About/primer/genetics_cell.html

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