Raymdnd P. Granville. aged 11 of Brooklyn.. N. Y. for his question:

What are chromosomes?

Plant and animal material is. all made of tiny cells. And every living; cell comes from a former living cell. Usually. the wonder of life is handed on by cell division.‑ A cell divides into two. making twins of itself. The miraculous. process is called mitosis  from the Greek word for thread. It is the way in which a new life begins‑. It is the way in which new. cells are added as a plant or your body grows.

A cell is filled with the magic life fluid called protoplasm. Under the microscope small bodies appear floating in this fluid. One tiny dark blob is. called the nucleus. Inside it is a mass of stuff. usually fine: grains. which becomes bright when dyed for microscope slides. It is named Chromatin from a Greek word for color. The little grains  or bodies. which form it are called the chromosomes

Every cell has a definite number of chromosomes. Each animal or plant carries its own special number in every cell. Corn carries 210. the onion carries‑16. the crayfish carries 200 and every human cell carries 48 chromosomes.  In them are the genes, those tiny bodies which order new cells; to copy their parent cells.

Let’s watch the process of mitosis. or cell dividing in the root tip of an onion. The change begins in the chromatin. The 16 chromosomes small grow into coiled threads like a ball of yarn. Soon each begins to split into two identical parts. Each chromosome has become twins the number has been doubled to 32.

Now begins a drill formation which is the most miraculous operation in all of nature. The round bundle becomes spindle shaped wide in the middle and tapering towards each end.  The chromosomes. now shorter and thicker line up in two equal rows. They face each‑other across the widest part. the equator of the spindle. Each pair of twin chromosomes is separated one in each‑line of 16.

As if by magic. the lines pull apart. They gravitate towards the narrow poles of the spindle and bundle together. Meantime the skin that bound the chromatin has gone. A new cell wall. appears between the two bundles of chromosomes. A living cell has become two living cells.  The onion has added one new cell to its growing root tip. And each daughter cell has a duplicate: of the chromosomes and genes which gave it the nature of an onion cell.

Animal cells go through mitosis in much the same way. Usually one chromosome. plays. a star role. This is the centrasome. It divides and it twins each move off at once to opposite poles of the spindle. Each seems­ wear a halo. called an aster from the Greek word for star. The other chromosomes divide line up and join the stars at the opposite ends of the cell. The original cell now pinches down the middle;. Two new cells each bearing a round bundle of chromosomes have been made. from one cell.