SECTION 14 



ANIMAL GENETICS AND BREEDING 



14.1. A Possible Case of the Genetic Assimilation of 

 Behaviour. Neville Moray, Kevin Connally 

 and Paul Arnold (London and Sheffield, 

 Great Britain). 



In 1961 Clutterbuck and Beardmore reported 

 that Drosophila melanogaster reared on media 

 containing peppermint oil, to which they were 

 aversive, became less aversive to the adulterant 

 over several generations. 



In a replication of this experiment with further 

 controls a stock of wild-type Drosophila me- 

 lanogaster were artificially selected for aversion 

 or non-aversion to peppermint. These two groups 

 and two unselected groups were divided into two 

 and reared either on normal food or on food 

 adulterated with peppermint oil. The offspring 

 from each group were tested at each generation 

 for their aversion to peppermint. In the artificially 

 selected groups on normal food the degree of 

 aversion showed only a very slight upward trend, 

 the unselected control remaining almost con- 

 stant. The line "Unselected on peppermint" also 

 showed little change. 



In the lines which had been subjected both to 

 artificial and natural selection results were 

 striking. Non-aversive flies reared on peppermint 

 (artificial and natural selection in co-operation) 

 showed a marked decrease in aversion, resulting 

 in the almost complete extinction of the line. 

 Aversive flies reared on peppermint (artificial and 

 natural selection in opposition) also became less 

 aversive over six generations. 



When this line was released at F 6 onto normal 

 food, the degree of aversion remained the same 

 as those flies still left on peppermint. We suggest 

 that this effect bears similarities to the genetic 

 assimilation of a character which does not have 

 a threshold, as discussed by Waddington. 



14.2. Genetic Transmission of Alcohol Preference in 

 Mice. John L. Fuller (Bar Harbor, U.S.A.). 



Four inbred strains of mice and 6 interstrain 

 Fa hybrids were given access to 6 different con- 

 centrations of alcohol over a 6-day period. A 

 measure of preference was obtained by adding 1 

 (for elimination of negative values) to the loga- 

 rithm of the alcohol concentration correspond- 



ing to the midpoint of an animal's total accumu- 

 lated fluid intake from all solutions. Homoge- 

 neity of variance was demonstrated in the 

 group scores. No significant sex differences 

 were found. The mean scores of the pure strains 

 were: C57BL/6J, 1.74; C3HeB/FeJ, 1.61; 

 A/J, 1.39; and DBA/2J, 1.08. The C57BL/6J and 

 DBA/2J strains had significant general combin- 

 ing effects in their hybrids. However, specific 

 combining effects were greater indicating the 

 importance of non-allelic interactions in the 

 determination of the phenotype of the hybrids. 

 The variation between the hybrids in genetic 

 control of alcohol preference (or aversion) sug- 

 gests a similar variability in its physiological basis. 



14.3. Factors Affecting Mating Competition in 

 Mice. L. Levine (New York, U.S.A.). 



Albino males of strain, ST/Jax, were paired 

 with pigmented males of strain, CBA/Jax, 

 and placed in cages with single albino 

 females, St/Jax. The albino males fathered 83 

 per cent of the offspring. Cage size does not 

 appear to affect the results. When pigmented 

 females, CBA/Jax, were used, the albino males 

 fathered 70 per cent of the offspring. 



Single albino males were taken at birth and 

 reared with pigmented litters. At weaning, each 

 albino male was paired with one of its foster 

 brothers, and both were placed in a cage with 

 a single albino female. The albino males fathered 

 93 per cent of the offspring. When single pig- 

 mented males were fostered to albino litters 

 and treated as above, the albino males fathered 

 50 per cent of the offspring. 



Albino and pigmented males were fought in 

 round-robin fashion. In two separate series, 

 eleven matched males from each strain were 

 used. In the first series, the fights were concluded 

 at the end of the first submission or after thirty 

 minutes if no submission occurred. In the second 

 series, the fights were observed for thirty minutes 

 regardless of number of submissions. In the first 

 series, the initial fights included 5 albino vic- 

 tories, 3 pigmented victories, and 3 no-victories. 

 In the second series, the initial fights included 

 6 albino victories, 3 pigmented victories, and 2 

 no-victories. Thereafter in both series, the pig- 



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