review - Why study meiosis? It generates the genetic...

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Why study meiosis? It generates the genetic variation upon which natural selection acts. The process is ancient and fundamental for sexually reproducing organisms. Main point: the evolutionary value of sexual reproduction is in the making of genetic variation in the gametes. Spermatogenesis: generation of spermatozoa (described in the text) Within the mammalian seminiferous tubules an outer layer of spermatogonia divide by mitosis. The following cells are surrounded by Sertoli cells . Spermatogonia give rise to primary spermatocytes which undergo the first meiotic division. Secondary spermatocytes undergo the second meiotic division (are rarer in the sections). Spermatids are in the process of becoming spermatozoa (closer to the lumen). Spermatozoa are in the lumen center. Oogenesis: A mammalian ovary section will show follicles at different stages of maturation. 1. Many primordial follicles are selected to increase in size to form … 2. The primary follicle , whose oocyte undergoes the first meiotic division. 3. The secondary follicle oocyte undergoes the second meiotic division. 4. The Graafian (tertiary) follicle is at the periphery and ready to be ovulated. Theca cells (which produce estrogen) are in a ring around the follicle cells. Follicle (or granulosa) cells surround the ovum.
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This note was uploaded on 11/15/2011 for the course ZOL 320 taught by Professor Kopachik,w during the Fall '08 term at Michigan State University.

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review - Why study meiosis? It generates the genetic...

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