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Condensation of long double-helical DNAs is a sharp phase transition, which takes place within a narrow interval of condensing agent concentrations.[ref] Since the double helices come very closely to each other in the condensed phase, this leads to the restructuring of water molecules, which gives rise to the so-called hydration forces.[ref] To ...
Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis). The thick lines are chromosomes, and the thin blue lines are fibers pulling on the chromosomes and pushing the ends of the cell apart. The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3.
Chromosome segregation is the process in eukaryotes by which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus. This segregation process occurs during both mitosis and meiosis. Chromosome segregation also occurs in prokaryotes ...
The nucleosome is the basic unit of DNA condensation and consists of a DNA double helix bound to an octamer of core histones (2 dimers of H2A and H2B, and an H3/H4 tetramer). About 147 base pairs of DNA coil around 1 octamer, and ~20 base pairs are sequestered by the addition of the linker histone (H1), and various length of "linker" DNA (~0 ...
In the latter experiments, the activity of individual condensin complexes on DNA was visualized by real-time fluorescence imaging, revealing that condensin I indeed is a fast loop-extruding motor and that a single condensin I complex can extrude 1,500 bp of DNA per second in a strictly ATP-dependent manner.
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
Thus, acetylation of histones is known to increase the expression of genes through transcription activation. Deacetylation performed by HDAC molecules has the opposite effect. By deacetylating the histone tails, the DNA becomes more tightly wrapped around the histone cores, making it harder for transcription factors to bind to the DNA.
Human reproduction naturally takes place as internal fertilization by sexual intercourse. During this process, the man inserts his erect penis into the woman's vagina and then either partner initiates rhythmic pelvic thrusts until the man achieves orgasm , which leads to ejaculation of semen containing sperm into the vaginal canal.