A SCIENTIFIC FIND

Evening Post, Volume CXXII, Issue 85, 7 October 1936, Page 18

A SCIENTIFIC FIND

GENERATOR OF CELLS

"SPINNING" THREADS

A hew mechanism in living cells which reveals a spinning process of the thread-like things— chromosomes— that govern hereditary, traits ; was announced recently at Cornell University, U.S.A., says the "New York

Times."

The mechanism is a dot, barely seen under a microscope, probably made of some unknown chemical. .. It. generates the nucleolus, one of the unsolved biological mysteries of the structure of living cells.

Human, animal, or plant, virtually, all cells contain nucleoli. These are tiny, j rounded, water-coloured objects like microscopic eyes floating in the clear; protoplasm of the nucleus, or inner compartment of every cell. ■ Where nucleoli come from and what ' work they do in maintaining lire has been guesswork. Recent studies have shown that they are important in cancer. They become relatively smaller , in malignant growths. | The discovery was made by Miss ; Barbara McClintock, a Cornell graduate of ten years ago. She proved, by splitting it with X-rays, that the tiny dot generates nucleoli. Each half of the dot thereupon' grew a separate nucleolus. Her work was done on maize cells. Here photographs show that the nu-' cleolus acts like a living basket made to hold the chromosome threads when the cells are "resting." During this | rest a cell is a rounded body of two | concentric shells. In it the nucleolus is clearly visible, but no chromosomes can be seen.

When the cell gets busy, either for growth or to transmit its life from parent to' offspring, the inner- shell develops a set of the chromosome threads. Simultaneously the nucleolus shrinks and almost disappears.

The threads split lengthwise. Half move to one side of the cell, half to the other. Then the cell itself divides, so that there are two complete cells, each with a full complement of chromosomes. In. this manner each of the billions of cells in a body contains an identical set of chromosomes, and a child gets a set half his father's, half his mother's.

1 The chromosomes- in the new cells disappear. Simultaneously'the- nucleolus reappears. Under. Miss McClintock's miscroscope are visible, substances which appear to be part of the 'chromosomes, and to come, from the "basket" when the'chromosomes.show up. The "basket" gathers up these substances when the chromosomes.disappear. . ■ .

This chromosome substance in the nucleolus is limited in volume. Miss McClintock showed this by the fact when the newly-found generator is split the two nucleoli'it forms are in total size equal only to one nucleolus. If the two touch in the cell they merge into a single nucleolus.

When she destroys the generating substance with X-rays no new nucleolus appears. Instead each chromosome tries to grow a separate nucleolus,- which-appears to be a crude knot of the chromosome spinning stuff.