Illustration of Laws of inheritance

1865 Laws of inheritance

The book of science

Tom Sharp

Gregor Johann Mendel genetics Illustration of Laws of inheritance

Laws of inheritance

Gregor Mendel meddled pairing peas patiently developing his principles. But many thought inheritance was not a matter of arithmetic or chance, at least among decent people, who had their own explanations for good blood and bad.

Mendelian factors

Morality is the recessive factor. A businessman considers the economics of a decision above all. A company teaches the needs of the company, as a church preaches the needs of the church. The artist who sacrifices his family for his art, the professor whose students serve his ego, the criminal whose desires are stronger than his fears, the wife who exempts her husband from what she expects of others, the father who exempts his children, the sister who exempts her brother, the neighbor who exempts her neighbor, the soldier who exempts the general, the voter who exempts the president, the policeman who doesn’t care, the uncle who doesn’t care, the doctor who is in it for himself, the accountant who sees the error but is paid to keep it quiet, combine and recombine, and chances are pure chance produces a happy citizen.

Pattern recognition

The pattern of repeating colors in generations of peas, the layout for a book on scientific discoveries, Christopher Alexander’s architectural vocabulary, Vogue dress patterns, molds for mass production of plastic fashion models, model cars, real cars, ideas of cars, cartoon, camera, computer, folk, classical, country, rock, disco, punk, paper clip, creative process, and poetic form, once established, once named, becomes obvious. Yet, given a diagnosis of lymphoma and actuarial tables, we want to think of only exceptions to the pattern. In the forest, the eye ignores the mass of leaves and focuses on the berries. Some are poisonous. Different diagnoses have similar symptoms. Diagnostic tests have false negatives and false positives. If the first doctor disappoints you, get a second opinion. Doctors were wrong about great grandpa Sharp, who went home, got drunk, and died of old age years later. A friend of a friend had an even worse case and now she is completely cured. Differences between individuals are greater than differences between groups. It runs in the family (easy to say), but she is an individual (easy to say). She must decide for herself. Chance does better than most economic advisors, and how well do doctors know anyone? They might as well say, “She’s happy; she’ll live as long as she likes.” Later, if her condition worsens, then she won’t be so happy. Instead, she’ll be ready to accept the doctor’s opinion and no one will be able to tell if it’s wrong because a life is not a double-blind scientific study.

Mendel’s work was pretty much ignored, but by 1900 or 1901 Hugo de Vries, Erich von Tschermak, Carl Correns, and William Jasper Spillman separately rediscovered it.

The laws of inheritance are so important that everyone who is the result of generic inheritance should know them:

  1. The law of segregation—Every person has two copies of the genes for each trait and passes only one copy at random to each child. When the copies from each parent are different, one is dominant. Traits are not blended.
  2. The law of independent assortment—Selecting the copy of one gene has nothing to do with selecting the copy of another gene.

Some plant and animal species reproduce without sex, but single-parent transmission does not follow the Mendelian laws of inheritance. Some species alternate between asexual and sexual reproduction. Inquiring minds want to know why plants do it, or as Cole Porter wrote, birds do it, bees do it, even educated fleas do it, why don’t we do it? Sexual reproduction increases genetic variation, which, for example, makes a species less susceptible to disease.

See also in The book of science:

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