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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