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The amount of DNA that comprises the haploid genome for a given species. Diploid cells that result from fertilization have the 2C value until they enter the S phase of their cell cycle (q.v.). Following S, they will have the 4C amount until mitosis produces two sibling nuclei, each with 2C. In species where females are XXAA and males XYAA (A = one set of autosomes), the diploid nuclei of females usually contain more DNA than male nuclei because the X chromosome has more DNA than the Y. In Drosophila melanogaster, for example, measurements reported in 1980 by P. K. Mulligan and E. M. Rasch show that male nuclei have about 90% the amount of DNA contained in female nuclei. The genome sizes published for most organisms do not differentiate separate values for the two sexes. The table illustrates the large range in the C values found among multicellular organisms. See Chronology, 1948, Boivin, Vendrely, and Vendrely; 1950, Swift; Genome Sizes and Gene Numbers; cell cycle, chromosome set, C value paradox, genome size.

Subjects: Genetics and Genomics.

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