Punnett Information Resources

Reginald Punnett (1875 – 1967)

Professor Reginald Punnett was a British professor of genetics at Cambridge. He was the oldest son of a builder and for much of his childhood he suffered from terrible bouts of appendicitis, which gave him the opportunity to stay at home and read his father’s natural history books. This led to an interest in natural history from an early age. Punnett completed both undergraduate and masters degrees in zoology at Gonville and Caius College, Cambridge. Between his undergraduate and masters degrees, Punnett took a part-time lectureship at St. Andrews University. Whilst undertaking his undergraduate degree, Punnett conducted work on the morphology of ribbon worms. Ultimately Punnett had two genus of marine worms named after him - Punnettia splendia and Cerbratulus punnetti. He co-founded the journal of Genetics in 1910 along with William Bateson.

Whilst undertaking his masters degree at Cambridge, Punnett forged a scientific collaboration with William Bateson, who at the time was using studying Mendelian inheritance in butterflies. The two were responsible for establishing the newly created field of genetics at Cambridge University. Punnett’s main collaborative role was to make sense of the statistics behind Mendel’s inheritance. The result was the ‘Punnett Square’.

Punnett is most famous for the ‘Punnett square’ diagram, which he intended to be used by biologists and geneticists to determine the chance of an offspring inheriting a particular genotype. This diagram is drawn in the form of a table into which all possible permutations of alleles from the X and Y-chromosomes are input, in order to determine the ratio of inheritance. As is convention within biology, dominant alleles are shown with upper-case letters (e.g. B) whereas a recessive allele will be shown with a lower-case letter (e.g. b). Since organisms have one maternal and one paternal allele, it is possible to have BB, Bb or bb configurations. In this example ‘B’ will stand for brown hair and ‘b’ will stand for blonde. Since brown hair is dominant over blonde hair, individuals with BB or Bb configurations will have brown hair. Only those with bb configurations will be born with blonde hair. The ratio for the scenario above is 3:1, brown: blonde. This is characteristic of a monohybrid cross.

Punnett’s academic interests included examining the concept of one species mimicking another for adaptive advantage in his studies of butterfly mimicry. Punnett believed that mimic species emerge because of unique mutations rather than through small continuous variations within the species. During the First World War, Punnett was called on to be a poultry expert, identifying the sex of newly hatched chicks (the males were killed soon after hatching to conserve the limited food for the hens). He was able to identify the sex by examining the plumage colours of the chicks, which had been specifically bred to have differing colours according to their sex. Punnett continued his poultry genetic research well into the 1950’s.

Punnett’s methodology typified the broader shift in biological sciences from descriptive fieldwork to experimental research in the laboratory. Although famous for devising the ‘Punnett Square’, he should also be remembered for being part of the generation to reinvigorate Mendel’s genetic concept, creating the fundamentals of the discipline.