SHORTER ARTICLES AND DISCUSSION 



THE APPEARANCE OF KNOWN MUTATIONS IN OTHER 

 MUTANT STOCKS 



In Drosopkila ampelophila the reappearance of known muta- 

 tions in stocks that appear to be uncontaminated is a not un- 

 familiar occurrence, but we discount all such cases unless in some 

 way the occurrence can be controlled, because the chance of con- 

 tamination even with extreme rare might be claimed to be greater 

 than the chance of mutating. 



In the stock of sepia-eyed Hies a few individuals with very pale 

 (yellowish red) eyes appeared. Sepia eyes are very dark or 

 black brown in color. So that the flies with the new eye color 

 stood out conspicuously amongst the dark-eyed sepias. 



From the color of the eye it was suggested that it might be 

 vermilion-sepia. If this were the case it should give, when bred 

 to vermilion flies, vermilion-eyed offspring, because the factor for 

 vermilion would be common to both stocks and the stock ver- 

 milion would carry the normal (dominant) allelomorph of sepia. 

 When the test was made the offspring were vermilion. These F^s 

 inbred gave in F 2 122 vermilion to 39 vermilion sepia, approxi- 

 mately 3 : 1, which is the expectation for one factor difference. 

 The result shows that a mutation to vermilion eyes had taken 

 place in stock that had already sepia eyes. The resulting flies 

 were the double recessive vermilion sepia. 



That the result is not due to contamination is evident, for had 

 a vermilion-eyed fly got into the sepia stock it would have 

 produced red-eyed (wild type) females or vermilion males. As 

 no red- or vermilion-eyed flies were present this explanation is 

 excluded. 



A similar mutation took place in stock having purple eyes. 

 Like sepia the eye color of these flies is dark but in this case 

 has a distinct purplish-red tinge. Among the offspring from a 

 cross of a female heterozygous for purple with a pure purple 

 male a fly with very pale orange-colored eyes appeared. This fly, 

 which was a male, was also conspicuously unlike the remainder 

 of the red or purple offspring of this pair. 



It was at first thought possible that this was the appearance 



case we should expect that in a cross to a cherry female all of F 1 

 offspring would be cherry. The test showed instead all cherry 

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