GIANTS IN GENETICS

Gregor Mendel, through his work on pea plants, discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits. He recognized the mathematical patterns of inheritance from one generation to the next. Mendel's Laws of Heredity are usually stated as:

1) The Law of Segregation: Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.

2) The Law of Independent Assortment: Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another.

3) The Law of Dominance: An organism with alternate forms of a gene will express the form that is dominant.

The genetic experiments Mendel did with pea plants took him eight years (1856-1863) and he published his results in 1865. During this time, Mendel grew over 10,000 pea plants, keeping track of progeny number and type. Mendel's work and his Laws of Inheritance were not appreciated in his time. It wasn't until 1900, after the rediscovery of his Laws, that his experimental results were understood.

Reginald Punnett

Reginald Punnett was born in England. As a young boy, Punnett suffered from appendicitis. During one of his recuperative periods, he started reading a series of books - Naturalist's Library. His father had bought the books because of the elegant binding; Punnett was fascinated by the subject. Although he went to Cambridge University as a medical student, Punnett graduated with a zoology degree in 1898. After graduation, Punnett continued at Cambridge as a researcher. He did work on the morphology of nemertine (ribbon) worms. Punnett has two species of marine worms named after him, Cerbratulus punnetti, Punnettia splendia.

While at Cambridge Punnett became interested in the experimental process, and wrote to William Bateson who was doing Mendelian experimentation on plants and animals. This began a scientific collaboration which helped establish genetics" at Cambridge. Bateson and Punnett published the first account of gene linkage in sweet peas and Punnett developed the "Punnett Square" to depict the number and variety of genetic combinations.

Punnett had a role in connecting Mendelism with statistics. In 1908, Punnett was asked at a lecture to explain why recessive phenotypes still persist — if brown eyes were dominant, then why wasn't the whole country becoming brown-eyed? Punnett couldn't answer the question to his own satisfaction. He in turn asked his friend the mathematician, G. H. Hardy. Out of this conversation came the Hardy-Weinberg Law which calculates how population affects genetic inheritance.

In 1912, when William Bateson decided not to return to Cambridge, Punnett became the first Arthur Balfour Professor of Genetics at the university. He worked on the genetics of sweet pea, maize and poultry, developing many breeds. He even used linkage as a way to sex type baby chicks. Punnett continued to do experiments even after his retirement in 1940.

Punnett was a quiet, tolerant, cultured man who was excellent at all sport involving a small fast ball. At 80, he was still an active member of the Savile Club in London where he played snooker. He died at his home in Somerset, England at the age of 92.