The Occurrence of Three Recognized Color Mutations in Mice

Abstract

To sum up the facts above recorded it may be stated that: 1. A previously recorded mutation of the gray-bellied agouti pattern, known as white-bellied agouti, has arisen in two experiments on color inheritance in mice. 2. In experiment A it has arisen independently three times in a hybrid race of mice. 3. In this experiment there has been no selection in the direction of the mutation. 4. In experiment B it has arisen once in an inbred race in which selection was being carried on. 5. In this race the mutation represents a variation in exactly the opposite direction from that in which the selection was being made. 6. A recessive pink-eyed mutation has occurred in a closely inbred dilute brown race. A similar mutation has appeared in a hybrid race into which one animal from the dilute brown race probably introduced the mutation. 7. A mutation involving loss or suppression of the black producing factor has arisen in a stock of inbred wild mice. This has caused the appearance of brown agouti young. 8. The wild race in which this occurred is related to the hybrid race (see conclusion 2) in which the white-bellied agouti mutation appeared three times. The suggestion is offered that a tendency to germinal instability may have been transmitted by male 131 a common ancestor of both races.