CHROMOSOME MAPS 24 -3 



The simplest way to represent this ratio as a single figure is 

 I ^ riVlU • Table 24-2 summarizes this ratio for various calculated 

 combinations. These calculations are summarized graphically in 

 fig. 24-1. This graph can be used to determine the distance of alleles 

 from their centromeres if the different ratios, tt yrf ^^^ known 



I + II + in 



for various combinations. Table 24-3 shows the ratios for all possi- 

 ble combinations of the a/t , G/g, and AD/ad loci are: 



7AD X a ad = 0.462 



aGxag =0.490 



ADO X ad g = 0.693 



An examination shows that these ratios agree with the following 

 distances. 



Ratio a/a G/g AD/ad 



.693 23.6 6.25 11.25 



.490 23.6 6.25 



.462 23.6 11.25 



We conclude, therefore, that the a/x locus is 23.6 units from its 

 centromere, the G/g locus is 6.25, and the AD/ad locus is 11.25. The 



I II IlT ratio for the G-PN combination is 0.466. G and PN are 



not linked and since the distance of G from the centromere is known 

 to be 6.25 and the graph indicates that PN is 25.6 units from its cen- 

 tromere. The distance of PB from its centromere was calculated 

 from the graph in the same manner. 



The AD chromosome contains 6 marked loci and the distances 

 between them are indicated in fig. 24-2. The circled figures were 

 calculated from the graph and the others by the standard recom- 

 bination technique. 



