Word: sperms
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Dates: during 1970-1979
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Unless the extracted eggs and the husband's sperm ? usually obtained by masturbation ? are kept at the right temperature and pressure, free of contamination and in an appropriate culture medium (salts, nutrients and sometimes blood serum), fertilization will not occur. Explains the University of Pennsylvania's Benjamin G. Brackett: "You don't want the eggs to suspect they are out of the body...
Equally important, the sperm must be primed for fertilization or, in the technical term, capacitated. This means that the chemical inhibitors preventing the sperm from penetrating the egg must be removed from the surface of the sperm. How this trick is accomplished in the body remains a puzzle; some scientists think that the woman's secretions do the job. But in the lab, experimenters usually are able to prime the sperm simply by gently bathing them in a salt solution. There is also the critical matter of timing: neither eggs nor sperm have unlimited lifetimes, nor does the uterus remain...
...placed in a dish containing blood serum and nutrients, to which sperm is added for fertilization...
Unlike in vitro fertilization, which lets nature take its course (sperm from the father and an egg from the mother unite, albeit in a test tube), cloning is asexual, single-parent reproduction. Instead of being a mixture of genes from two parents, the clone (from the Greek word klon, meaning twig or slip) is a genetic copy of its single parent...
...mammals by the classic method is a long way off, scientists are moving closer to cloning mice by an indirect route. In this technique, devised by Yale Biologist Clement Markert, eggs are removed from a female mouse shortly after fertilization. At this early stage, genetic material from egg and sperm have not yet mixed; the mother's and father's genes are still in two distinct sacs, called pronuclei. Using microsurgery, Markert removes either pronucleus. The egg is then exposed to a chemical that causes the remaining pronucleus to replicate, thus giving the cell a full complement...