the main features of this chromosome are as follows : ( a ) it contains an sd ( ra ) gene with a moderate degree of segregation distortion ( k = 0.72 ) , ( b ) a recessive female sterile gene , fs ( 2 ) ( tlm ) , responsible for modifications of the morphology and structure of the tests and ovaries is located at 89.7 , ( c ) sd ( ra ) /sd ( ra ) males and females are viable but sterile , the females due to homozygosis of fs ( 2 ) ( tlm ) and the males because of homozygosis of a region containing the sd locus , and ( d ) sdi/sdj combinations are fertile , thus suggesting that the different sd factors found in natural populations constitute a multiple allelic series.-these data may indicate that each population containing sd chromosomes has evolved its own genetic architecture for the complex sd system , with specific modifiers and perhaps different sd genes .
C1708726
locus
C0008633
chromosomes