Yolk spherules

Unfertilized Lytechinus eggs contain roughly 200,000 mitochondria and 80,000 yolk spherules which also might be derived from mitochondria. The total DNA content of the egg was 8.3 pg for L. pictus and 3.3 pg for S. purpuratus (Piko et ah, 1967). In the Lytechinus egg 6.4 pg DNA are located within mitochondria and yolk spherules. According to a calculation of Piko et al. (1967) these mitochondria contain only one or two molecules of circular DNA with a circumference of 4.5 to 5 /nm and a density of 1.703 gm/cm . No unicircular dimers have been found in mt DNA preparations prepared from Lytechinus eggs. But besides 88% monomers, interlocked circles, or catenated oligomers (11% dimers, 1% trimers, 0.3% tetramers) are found. 

Cytoplasmic DNA, measured by newer methods that eliminate interfering materials, is less in amount than previously reported but still several times the nuclear DNA in sea urchins and in other animals. It is of special circular form, 4.5 jx in perimeter, and is located in the mitochondria and yolk spherules, one or two circles per particle. It has the same priming capacity for RNA synthesis as nuclear DNA. Knowledge... 

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