Dna density in mitotic and meiotic metaphase chromosomes of plants and animals

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Abstract
Studies of chromosome disposition at metaphase using serial thin-sectioning and threedimensional reconstruction techniques have produced accurate estimates of the total volume of chromosomes per cell in 15 plant and two animal species. Comparing this character with the 4C DNA amount showed no indication of systematic differences in DNA density between either organisms with widely different (>200-fold) C values or different groups or organisms. For example, there was no significant difference between the density of DNA in somatic metaphase chromosomes of man (0·141 pg/ μm3) and its mean in 14 angiosperm plant species (0·182pg/ μm3), or between four dicotyledons (0·180 pg/ μm3) and 10 monocotyledons (0–182pg//tm3). However, evidence was found showing that DNA density can vary significantly within a species. Thus, although the total chromosome volume per cell was closely correlated (r>0·97) with 4C DNA amount in somatic and meiotic cells, the density of DNA in metaphase chromosomes was significantly lower in meiocytes (0·131 pg/ μm3) than in somatic metaphase cells (0·179pg/ μm3).