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...And to muscle.

. . . and to muscle

A gene for a protein found in muscle of older embryos is activated in Xenopus development slightly later than the genes for keratin. John B. Gurdon of Cambridge (England) University reports this gene is turned on only in the cells that eventually become muscle. The specification of this gene activity, like that of genes studied by Douglas Melton (see above), appears to be spatially determined in the original egg. Gurdon and his colleagues have cut the fertilized egg into various zones. They find that the part of the egg necessary for musclegene activation lies just below the egg's equator.

Studies of the embryo at the 32-cell stage demonstrate that cells in an equatorial band, which make up two out of four tiers of cells, normally can develop into muscle. But Gurdon reports that if the embryo is cut on the equator between the two muscle-making tiers (called tiers 2 and 3), only the lower of the two tiers can form muscle. The higher tier now forms skin and nerve. He concludes from additional experiments that a muscle-inducing substance is located in tier 3, and it diffuses into tier 2 when the cells are in contact.
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Title Annotation:embryo development
Author:Miller, Julie Ann
Publication:Science News
Date:May 24, 1986
Words:198
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