Reginald Crundall Punnett

• Born: June 20, 1875
• Birthplace: Tonbridge, Kent, England
• Died: January 3, 1967
• Place of death: Bilbrook, Somerset, England

Background

Twentieth-century British geneticist Reginald Crundall Punnett was one of the world's foremost authorities on poultry breeding during the twentieth century. He promoted the principles of heredity, as discovered by Gregor Mendel, which advanced the developing discipline of genetics. He also conducted many experiments in heredity with British biologist William Bateson.

Punnett is probably best known for designing a simple graphical method for predicting heredity patterns, called the "Punnett square." It has become the standard tool for introducing students to the study of genetics.

Reginald Punnett was born in Tonbridge, England, on June 20, 1875. He was the eldest son of Emily Crundall Punnett and George Punnett, who worked in the construction industry.

Punnett graduated from a preparatory school in Tonbridge and then entered Clifton College, where he majored in classics. Upon graduation, he earned a scholarship to study medicine at Gonville and Caius College at the University of Cambridge. However, a course in zoology convinced him to switch majors, and in 1898, he graduated first in his class with a bachelor's degree in zoology.

After graduation, he researched nemertines, or "ribbon worms" that live mostly in marine environments; some species grow to lengths as impressive as one hundred feet. His work took him to the Zoological Station in Naples, Italy, and to laboratories in Germany, England, and Scotland. He wrote several papers on the morphology of nemertines, and had two worms named after him.

Punnett lectured part-time at the University of St. Andrews in Scotland, and returned to Gonville and Caius to teach zoology in 1901.

In 1900, scientists discovered a paper written more than thirty years earlier by Gregor Mendel, an Austrian monk. The work detailed a series of pea plant experiments on which his laws of genetic inheritance were based. For Darwinian evolutionists, such as Punnett, the paper explained the mechanics of evolution.

In 1902, Punnett contacted William Bateson, professor of biology at Cambridge, who was conducting Mendelian research on plants and animals. Bateson had already performed many monohybrid experiments on chickens and pea plants, in which he had chosen one trait at a time to cross. His results duplicated and supported Mendel's work. Punnett assisted Bateson in these experiments and many others.

In 1905, Punnett wrote the first textbook on Mendel's theories, Mendelism. Along with Bateson, he became one of the greatest promoters of Mendel's work, and worked to convince the scientific community of the value of Mendel's principles of heredity.

Punnett Squares and Linkage

Punnett worked with Bateson for about six years, during which time the pair experimented with dihybrid crosses, in which they bred animals and flowers based on two traits. During these experiments, they noticed that in some cases, offspring would always exhibit the same two traits. For instance, red flowers and round-shaped pollen were typically found together in pea plants. Unlike Mendel, who had theorized that all traits were inherited separately, Bateson and Punnett concluded that some traits are inherited as a unit, or linked together. It was later determined that this type of inheritance, called "linkage," occurs when more than one gene is located on a chromosome.

Bateson and Punnett performed monohybrid and dihybrid crossbreeding experiments on many animals, including rabbits, lambs, guinea pigs, goats, and mice. The results of these animal experiments confirmed that Mendel's principles of heredity also applied to the animal kingdom.

In presenting the results of the research, Punnett used a simple square, or diagram, to illustrate the results of each crossbreeding experiment. Other scientists began to refer to these diagrams as "Punnett squares," and soon they were being used in biology and genetics courses to predict results for phenotypes, or the expression of inherited traits.

To predict the outcome for a simple experiment in which pea plants are crossed for the genotype, or trait, of seed shape, a table can be created with three rows and three columns, forming a total of nine cells. Parent A has round seeds, which is the dominant trait. The alleles, or gene pair, are designated "RR." Parent B has wrinkled seeds, which is the recessive trait. The alleles are represented by the lower case letters, "rr."

The alleles of Parent A are entered in the top row of the square, leaving the first cell blank. The alleles of Parent B are entered in the left column, leaving the first cell blank.

The results of the crossing can be depicted by carrying forward the letters at both the top of the column and the side of the row into the blank cells to complete the table.

In this case, all offspring inherited both alleles, which resulted in the genotype "Rr." Since the dominant trait "R" is present in each, 100 percent of the offspring will express the round seed. However, each offspring also carries the recessive allele for wrinkled seeds, which could be expressed in future generations if crossed with plants that don't have the dominant allele.

Here is the Punnett square for a crossing of this generation with plants with wrinkled seeds ("rr"):

For this generation, only 25 percent of the offspring would inherit the dominant trait, and would have round seeds. The other 75 percent would be wrinkled.

Mimicry

Like Bateson, Punnett was an evolutionist who did not believe that speciation had occurred in a gradual, continuous manner as theorized by Charles Darwin. Instead, both Punnett and Bateson believed in the theory of discontinuity, or that speciation and variations occurred sporadically, in bursts. To find additional support for this theory, Punnett began to research mimicry in butterflies.

Mimicry occurs when animals take on physical characteristics of their environment or other animals, such as a camouflage or other protection that will ensure their survival. An example of butterfly camouflage can be witnessed when certain species land on a pile of leaves or a tree trunk, and with their wings wide open, they blend in.

Punnett studied examples of butterfly mimicry around the world, and theorized that mimicry is a type of variation that also occurs in bursts or in a discontinuous manner. His research was published in 1915 as Mimicry in Butterflies.

During this decade, Punnett was appointed superintendent of the Museum of Zoology at Cambridge. In 1910, he succeeded Bateson at Cambridge in a newly-created position, the Arthur Balfour Chair of Genetics.

In 1911, Punnett and Bateson founded the Journal of Genetics, which was the first periodical published in the discipline. Punnett was elected a fellow of the Royal Society in 1912, and later received its Darwin Medal in 1922.

During World War I, Punnett used his knowledge of animal breeding to help alleviate food shortages. While employed in the Food Production Department of the Board of Agriculture, he bred chickens so that the gender of the newborns chicks could be identified at a glance by the color of the plumage. Many male chickens, which could not produce eggs and thus did not warrant feeding, were destroyed. The fact that plumage color is tied to physical sex, or sex-linked, is another example of linkage.

After the war, in response to the initiatives undertaken by Punnett, Cambridge became known for poultry breeding. In 1923, Punnett published Heredity in Poultry, which became the standard work for decades. As research in heredity progressed, Punnett was able to produce an early map of the X chromosome in chickens and identified several genes.

An early member of Great Britain's Genetics Society, Punnett served as the organization's second president from 1930 to 1932. He also reportedly received honorary membership in a Japanese genetics association and the Poultry Science Association of America.

Punnett retired in 1940. Soon thereafter, he moved to Bilbrook, Somerset, where he continued his poultry breeding experiments until 1955.

Punnett was married to Eveline (Froude) Punnett, a former widow, from 1913 until her death in 1965. He died at home on January 3, 1967, at the age of ninety-one.

Bibliography

Crew, Francis Albert Eley. “Reginald Crundall Punnett, 1875-1967.” Biographical Memoirs of Fellows of the Royal Society, vol. 13, Nov. 1967, pp. 309–26, doi:10.1098/rsbm.1967.0016. Accessed 30 Oct. 2020.‌

Edwards, A. W. F. “Reginald Crundall Punnett: First Arthur Balfour Professor of Genetics, Cambridge, 1912.” Genetics, vol. 192, no. 1, Sept. 2012, pp. 3–13, doi:10.1534/genetics.112.143552. Accessed 30 Oct. 2020.‌

“Reginald Crundall Punnett.” DNA from the Beginning, Cold Spring Harbor Laboratory, 2011, www.dnaftb.org/5/bio.html. Accessed 30 Oct. 2020.‌