COLOUR OF A MOUSE

Manawatu Times, Volume LIV, Issue 6944, 25 June 1929, Page 3

COLOUR OF A MOUSE

Not Due io Heredity

Mice of almost any colour desired arc being “made” at Columbia University as the result of research in heredity by Leslie 0. Dunn, professor of /.oology, who found that the colour ol' the common house mouse is not duo to heredity, but to the rate of changes which take place in the Idoud and cell tissue shortlv after birth.

These experiments have resulted in a clarification of one of the problems which have baulked scientists who are attempting to better the human stock through heredity. The ultimate goal is to learn just how the traits of the individual are inherited, and mice arc used in the laboratory because they arc easy to work with and to keep in confinement, and arc similar in many respects to human beings. Professor Dunn has applied the laws of heredity set forth by Mendel, who began his; experiments into the subject with garden peas. The discovery of Mendel's work in tile journal of a small natural history society of Brunip in what is now Czccho-Slovakiu, created a stir in the scientific world in 3 900. It had been overlooked for many years, but siuce the turn of the century scientists have been steadily working out Mendel’s findings. Fourteen to 13 generations of mice are required to permit any definite conclusions as to tlieir heredity, according to Professor Dunn. Six or seven generations of mice cuu be produced in the laboratory a year.

“Most of the varieties of mice known, of which about L’UOO exist, or can be produced, are descended from tlie wild house mice,” said Professor Dunn. “It is possible to produce mice of any desired shade of skin or eye. Once you know the inheritance of the individual, by proper combining, you can put any coat you like on the offspring. “Although tho fundamental laws of heredity ore known, scientists arc now Studying the width of the application of these laws, 'flic chief problem today is to determine the process by which the multitude of the physical variations are derived from tlie original germ cell. “The lowest elements of living matter are genes,” Professor Dunn said. "These arc the invisible units of the elironosornes which exist in the germ cells. They probably number thousands in each cell. Each gene is in some way responsible for a particular trait in the resulting individual. “There are, for instance, in mice, genes which arc responsible for the ultimate colour of the coat, whether it bo yellow, black, brown, spotted, albino, or of the common grey mouse va-. ricty. What science is endeavouring to irace is how these genes operate in bringing about the result. Chaugc after Birth “An entirely different technique from that of the chemist has to be employed in its study. All mice are the same colour at birth. After a few hours, however, they develop into their predetermined colours. These colours are the Tcsult of the oxidation of specific colourless bodies or compounds which have been discovered in their skin, and which owe their existence to the genes in the original germ cell. “German scientists recently have perfected a chemical substance which acts like a photographic developer upon these bodies, bringing out in combination with them the characteristic tone of the skin. Experiments with this substance are permitting biologists to make definite-»deductions in regard to development of specific traits. “According to these observations it seems possible that the resulting colour of the coat may be due to no aittual difference in the hereditary background, but rather to tile rate at which changes in the 'blood and cell tissue have taken place. The gene responsible for the skin becoming black and spotted may have operated merely by determining a certain acidity in the blood at a crucial stage of develop- “ Observation has proved that mice, of different colours may have only a comparatively email number of genes that differ. The albino may have a heredity such that he is in reality a potential black mouse, or a yellow mouse, or a spotted mouse, by lacking but one of the genes necessary to confirm his colour. By discovering what one gene is lacking, and mating the albino with another albino in which this

gene is present, a coloured mouse may be produced.” Describing his previous studies of fowls, Professor Dunn said lie had carried on experiments in inbreeding with fowls over a period of years, constantly mating brothers and sisters. The immediate results of inbreeding were invariably weak individuals lacking in vigour, but when two such inbred individuals were in turn combined the offspring possessed all the vigour of the original stock. “When the results of experiments with the inbreeding of fowls were first published,” the zoologist said, “they created a sensation among the poultry breeders. Instead of having to go into the market from time (o time in search of new blood to reinvigoratc his poultry, the poultr.vman saw himself able to accomplish the desired result by inbreeding and crossing his own stock. “But the law of the laboratory did not always hold good on the farm. Faced with disappointment, the fanner often discovered that he lacked the exact methods, the unerring personal observation of his brood, and the sure judgment -which could produce results in keeping with the scientist ’s findings. “So it is in the application of studies of human heredity to the social group. If those who apply them are less than infallible, great wrong and failures may ensue.” Professor Dunn believes that in the end the human stock will lie aided rather than hurt from the present humanitarian ideal which lias placed delects on the increase rather than on the decrease. lie believes segregation will take care of the hopelessly defective, and prevent them from creating new defectives.

'‘Birth control, properly understood, will accomplish the rest. Economic causes are responsil.de for conditions which may in some instances be responsible for accidental defectiveness.”