GENE CONVERSION 



26-8 



GENETICAL ANALYSIS OF TRANSFORMED ME ALLELES 



Table 26-4 shows the analysis of ascus 550-551-552-553 which 

 was obtained from a hybrid heterozygous for G/g ME/me and MA/ma 

 alleles. Regular segregations of the G and MA alleles occurred, 

 but the ascus was ME ME ME ME. These data are summarized be- 

 low. 



550 gMEMA 

 X me 



6 ME, 5 me 

 2 MEMEmeme 



551 GMEma 

 X me 



6 ME, 4 me 

 1 MEMEmeme 



552 gMEma 

 X me 



4 ME 



1 MEMEMEME 



553 GMEMA 

 X me 



6 ME 



550 X 553 



5 ME, 5 me 

 1 MEMEmeme 



552 X 553 



15 ME, 1 me 

 3 MEMEMEME 

 1 MEMEMEme 



Backcross to the nonfermenter (me) revealed that 550 and 551 gave 

 regular ratios; these two clones acted like regular dominants. How- 

 ever, 552 and 553 backcrossed to the nonfermenter threw only a 

 dominant progeny, indicating that the ME alleles in 552 and 553 had 

 the ability to transform nonfermenters into fermenters. A mating 

 of 552 X 553 (ME x ME) produced 15 ME and 1 me clones, indicat- 

 ing that they were strong dominants. However, mating 550 to 553 

 (ME X ME) gave only ME ME me me asci, suggesting that 550 was 

 a weak dominant which easily lost its fermentative ability. This 

 might indicate that 550 had recently acquired its fermentative 

 ability. 



TESTS FOR CYTOPLASMIC EFFECTS 

 (WITH THE COOPERATION OF DR. DOUDOROFF 

 AND OUR STAFF) 



The tetrad analyses presented in Chapter 25 have shown that 

 irregular ratios of the type described in the preceding section can 

 be interpreted as the result of the direct transfer of material from 



