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果蝇是双翅目昆虫,属果蝇属,约九百多个种。通常做遗传学实验材料的是黑腹果蝇。果蝇唾腺染色体的体积比体细胞常染色体的体积大1000多倍。4个配对的染色体组总长度为2000μm,而相同体细胞常染色体为7.5μm。唾腺染色体的巨大直径是由于它们是许多纤维所形成的缘故。每条染色体起始时有4根纤维,以后经过多次分裂仍然保持在一起,好象一根绳子里许多细线一样。纤细而难以观察的每一根纤维,可以认为是一根染色质线。纤维的再复制过程,称做内有丝分裂。大约经过10次再复制,就可产生2~(10)=1024根
Drosophila is a Diptera insects, is a genus Drosophila, about nine hundred species. Drosophila melanogaster is commonly used as a genetic test material. Drosophila salivary gland chromosome volume than the somatic autosomal size larger than 1000 times. The total length of the 4 paired chromosomes was 2000 μm, while the same somatic autosome was 7.5 μm. The huge diameter of salivary gland chromosomes is due to the fact that they are formed by many fibers. Each chromosome initially has 4 fibers that remain split together after multiple breaks, as if many of the thin wires were on the same rope. Each fiber, which is slender and hard to see, can be thought of as a chromatin line. Re-replication of fiber, called mitotic. About 10 times and then copy, can produce 2 ~ (10) = 1024 root