The capacity of silk production was essentially controlled by the replication frequency of DNA of the silk gland throughout its development, although productivity of silk, properly speaking fibroin of silkworm, Bombyx mori, was in proportion to the amount of RNA accumulation in the posterior silk gland. From the data on the amount of silk gland DNA in the fully grown larva, its replication frequency was calculated as 29 times and 30 times for a line of low productivity and a line of high productivity of silkworm varieties, respectively. In some cases, juvenoid would be able to make a chance to increase a replication frequency of chromosomal DNA. A DNA molecule can transcribe RNA ranged from 4 to 8 pg.
　Certain alteration in the capacity of RNA synthesis took place among silkworm varieties, due to genetic difference of larval body and to different rearing environment. It is essential to take account the transcriptional control.
　Abnormal states such as starvation caused a severe alteration in translation phase and the efficiency of RNA for silk synthesis was reduced remarkably. Thus lowering translation activity may be brought about by quantitative imbalance of RNA species.
　From our experiments quantitative relationship between nucleic acids and silk production of the silkworm is synthetically presented as shown in Fig. 3.