Nevertheless, the gene for blue eyes may be passed on from generation to generation, unnoticed but unchanged. The potentialities of a race are passed on unchanged-except for mutation-from parent to child. They may be shuffled and dealt and shuffled again, producing an inconceivable number of unique individuals, but the genes are unchanged.
Chess men may be arranged on the board in many combinations, but the unit men do not vary. Fifty-two playing cards may be dealt to produce an enormous number of different hands, but the cards are the original fifty-two. One hand may be full of high cards; another may be worthless — pure chance.
But suppose you were permitted to make up the best hand of five cards possible out of the first ten cards dealt? The chance of getting the best possible hand has been increased two hundred and fifty-two times! (Check it.)
Such is the method of racial improvement by gene selection.
A life-producing cell in the gonads of a male is ready to divide to form gametes. The forty-eight chromosomes intertwine frantically, each with its opposite number. So close is this conjugation that genes or groups of genes may even trade places with their opposites from the other chromosomes. Presently this dance ceases. Each member of a pair of chromosomes withdraws from its partner as far as possible, until there is a cluster of twenty-four chromosomes at each end of the cell. The cell splits, forming two new cells, each with only twenty-four chromosomes, each containing exactly half of the potentialities of the parent cell and parent zygote.
One of these cells contains a chromosome-the X-chromosome-which declares that any zygote formed with its help will be female.
The two cells divide again. But in this fission the chromosomes themselves divide, endwise, thereby conserving every gene and every one of the twenty-four chromosomes. The end product is four wigglers-male gametes, spermatozoa-half of whom can produce females; half, males. The male producers are exactly alike in their gene assortments and are exact complements of the female producers. This is the key point in the technique of gene selection.
The heads of the male producers average four microns in length; the heads of the female producers average five microns in length-another key point.
In the female gonad the evolution of the gamete, or ovum, is like that described for the male gametes, with two exceptions. After the reduction-division in which the number of chromosomes per cell is reduced from forty-eight to twenty-four the result is not two ova, but one ovum and one “polar body.” The polar body is a pseudo egg, containing a chromosome pattern complementary to that of the true gamete, but it is sterile. It’s a nobody that never will be anybody.
The ovum divides again, throwing off another polar body which has the same pattern as the ovum. The original polar body divides again, producing two more polar bodies of complementary pattern. Thus the polar bodies of pattern complementary to the ovum always exceed in number those of identical pattern. This is a key fact. All ova may become either male or female. Sex of the infant zygote is determined by the cell provided by the father; the mother has no part in it.
The above is a very rough picture. It is necessary to compress, to exaggerate, to omit detail, to use over-simplified analogy. For example, the terms “dominant” and “recessive” are relative terms; and characteristics are rarely determined by one gene alone. Furthermore, mutations-spontaneous changes in the genes themselves-occur with greater frequency than this account has emphasized. But, the picture is reasonably correct in its broad outlines.
How can these facts be used to produce the sort of man or woman one wishes to produce? Offhand, the question appears simple. An adult male produces hundreds of billions of gametes. Ova are produced on no such wholesale scale, but in quite adequate numbers. It would appear to be a simple matter to determine what combination you want and then wait for it to show up…or at least to wait for a combination near enough to be satisfactory.
But it is necessary to recognize the combination wanted when it shows up. And that can be done only by examining the gene patterns in the chromosomes.