Heredity, race, and society.

  • Leslie Clarence Dunn
Date:
1947
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity, race, and society. Source: Wellcome Collection.

    57/148 page 55
    not repeatable in the future. A biologist must assert the absolute uniqueness of every human individual. This same assertion, translated into metaphysical and political terms is fundamental for both ethics and democracy. A father and a mother transmit different sets of genes to each of their children. A human sex cell has one gene of each of the kinds which we have discussed (for eye color, taste reaction to PTC, albinism versus nor mal coloration, brachydactyly versus normal fingers), and, of course, one of each of the many other genes which the human species must have. We estimate that there must be several thousands of genes in the full set carried in a human sex cell. Fertilization of an egg by a sperm results in the development of the new individual. Since the baby gets one gene of each kind from each parent, it follows that it has two of each kind. If there are five thousand different genes in the egg and five thousand in the sperm cell, there will be five thousand pairs or ten thousand altogether in every cell composing the body of the individual. However, when sex cells, whether eggs or sperms, are formed in that individual there is an exact biological mechanism in the body which ensures that each egg or sperm will receive one gene of each pair. It is clear, therefore, that each parent transmits to its child always only l^, never all, the genes it has. The next child, developing from a different sex cell, will have also i/£> of the genes which each parent has, but it will be, as we know, a different set of genes for every child. An analogy may be helpful in understanding clearly the workings of the hereditary mechanism. The set of genes present in a sex cell may be likened to a suit of cards, except that the hereditary suit has several thousand, instead of the thirteen, cards. Suppose that the maternal cards are red and the paternal black. The child has two suits, a red and a black one. Now when the child grows up and produces its own sex cells, a full hand must be provided for each cell. But it does not matter whether only red, or only black, or
    digitised image 1
    digitised image 2
    digitised image 3