If you're seeing this message, it means we're having trouble loading external resources on our website. If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. 1. Before mitosis and cell division, in order to produce an exact copy of itself, DNA must be replicated. This happens during the S phase. 2. There are 4 nucleotides present in the DNA and there are pairs such as A = T and C = G. If there are 30% of A there must also be 30% of T for a total of 60% out of 100, this leaves us with 40% to share half with A and T each with 20%. 3. Same explanation with number 2, but this time for the other pair. 4. Hydrogen bonds occur between the two strands and involve a base from one strand with a base from the second in complementary pairing.
anaphase: the stage of mitosis during which sister chromatids are separated from each other cell cycle: the ordered sequence of events that a cell passes through between one cell division and the next cell cycle checkpoints: mechanisms that monitor the preparedness of a eukaryotic cell to advance through the various cell cycle stages cell plate: a structure formed during plant-cell cytokinesis by Golgi vesicles fusing at the metaphase plate; will ultimately lead to formation of a cell wall to separate the two daughter cells centriole: a paired rod-like structure constructed of microtubules at the center of each animal cell centrosome cleavage furrow: a constriction formed by the actin ring during animal-cell cytokinesis that leads to cytoplasmic division cytokinesis: the division of the cytoplasm following mitosis to form two daughter cells G0 phase: a cell-cycle phase distinct from the G1 phase of interphase; a cell in G0 is not preparing to divide G1 phase: (also, first gap) a cell-cycle phase; first phase of interphase centered on cell growth during mitosis G2 phase: (also, second gap) a cell-cycle phase; third phase of interphase where the cell undergoes the final preparations for mitosis interphase: the period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases; the interim between two consecutive cell divisions kinetochore: a protein structure in the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase metaphase plate: the equatorial plane midway between two poles of a cell where the chromosomes align during metaphase metaphase: the stage of mitosis during which chromosomes are lined up at the metaphase plate mitosis: the period of the cell cycle at which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase mitotic phase: the period of the cell cycle when duplicated chromosomes are distributed into two nuclei and the cytoplasmic contents are divided; includes mitosis and cytokinesis mitotic spindle: the microtubule apparatus that orchestrates the movement of chromosomes during mitosis prometaphase: the stage of mitosis during which mitotic spindle fibers attach to kinetochores prophase: the stage of mitosis during which chromosomes condense and the mitotic spindle begins to form quiescent: describes a cell that is performing normal cell functions and has not initiated preparations for cell division S phase: the second, or synthesis phase, of interphase during which DNA replication occurs telophase: the stage of mitosis during which chromosomes arrive at opposite poles, decondense, and are surrounded by new nuclear envelopes |