The blastula is a stage of growth of a fertilized animal egg. It has about 128 cells, and follows the formation of a blastocyst by the "morula" stage (it precedes implantation in the endometrium).
From my research I think the vegetal plate of the blastula ingresses upon the blastocoel region, to form a blastopore, which will eventually be the anus of the sea urchin.
A DNA occurs under greater dehydration than B DNA therefore it is more compact than B DNA, it also has 11bp/turn, the diameter is 23A, the plane of the bases is tilted at a 30 degree angle and the...