Genetic analysis of the Nd-s mutation in the silkworm, Bombyx mori.

Abstract
To investigate the distance between Nd-s and Fib-L on the 14th chromosome of B. mori, a 3 point test cross involving U, Nd-s and Fib-L was carried out. The crossover frequency between U and Fib-L or U and Nd-s was 24.6%. Crossing over between Fib-L and Nd-s was not observed. Evidently Fib-L is closely linked with Nd-s. In the fibroin slightly secreted into the lumen of the posterior silk gland of the Nd-s mutant silkworm, fibrin L-chain was not detectable. The possibility that the Nd-s phenotype is caused by a mutation in the L-chain gene is discussed.