Word: cytoplasmic
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Chemical Hostility. Danielli and his collaborators, Joan Lorch and Kwang W. Jeon, worked with the amoeba's three major components: the nucleus (central control center), the cytoplasm (gel-like body matter) and the cell membrane (outer wall). In a typical experiment, they carefully removed the nucleus of one amoeba with a microprobe and sucked out most of the cell's cytoplasm with a tiny pipette. Then they inserted into the remaining cell membrane a nucleus and cytoplasm that had been similarly removed from other cells. In more than 70% of their attempts, the transplant produced a completely viable...
Having ruled out both environmental and genetic influences, Williams can only suggest that there are "unknown factors" that affect heredity. Although the gene-bearing chromosomes duplicate themselves precisely in each new cell nucleus after the division of a fertilized egg cell, the little-understood structures and particles in the cytoplasm of the egg cell are not symmetrically arranged. During division, Williams suggests, one new cell may not receive the same quantity of the unknown factors as another, and the result is marked differences between the four armadillos-or between identical human twins-that eventually form from the same...
Kafatos points out that even if the nucleus of a fertilized egg is removed, the egg can still give rise to a very young embyro. This demonstrates that stable messenger RNA for making an embryo had been stored in the egg's cytoplasm. Storage may well be the level where the critical choice might reside in the cells of higher organisms. This is not the case for very simple cells like bacteria, where the genetic information is transcribed into RNA and immediately translated into protein. Kafatos explained that, due to the great instability of the bacterial world, bacteria...
...CONTRAST, the highly-differentiated cells of more developed organisms are much more stable. Once a cell is programmed to fulfill a specific role, it will continue to do so. In this case continual messages to the cytoplasm are superfluous. Kafatos has been able to correlate stability and differentiation. He made this important discovery in a research project which began with an undergraduate, Julianne Reich '67, a former Bio 15 student now at the Medical School. The gland on the moth's face which produces large amounts of a single enzyme is an example of a highly differentiated organ. About...
After investigating the stability of RNA, Kafatos turned to possible mechanisms for transporting the RNA to the cytoplasm. Extending his Widener metaphor, he said the first possibility is similar to a Cliffie going into the stacks to obtain the book herself while the second is like her using the library's call system, having the book delivered up to the reading room. In the first possibility, the actual users of the genetic information, the ribosomes, or protein-synthesizing particles, may carry messenger RNA from the nucleus to the cytoplasm, the cite of protein synthesis. Second, there may exist a distinct...