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In eukaryotes, such as humans, roughly 3.2 billion nucleotides are spread out over 23 different chromosomes (males have both an X chromosome and a Y chromosome instead of a pair of X chromosomes as seen in females). Each chromosome consists enormously long linear DNA molecule associated with proteins that fold and pack the fine thread of DNA ...
A chromosome is a package of DNA containing part or all of the genetic material of an organism.In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most important of these proteins are the histones.
In eukaryotes, haploid gametes are produced by meiosis; two gametes fuse to form a diploid zygote. Eukaryotes have a life cycle that involves sexual reproduction, alternating between a haploid phase, where only one copy of each chromosome is present in each cell, and a diploid phase, with two
Throughout the eukaryotic kingdom, the overall structure of chromosome ends is conserved and is characterized by the telomeric tract - a series of short G-rich repeats. This is succeeded by an extensive subtelomeric region consisting of various types and lengths of repeats - the telomere associated sequences (TAS). [ 1 ]
Eukaryotic DNA must be tightly compacted in order to fit within the confined space of the nucleus. Chromosomes are packaged by wrapping 147 nucleotides around an octamer of histone proteins, forming a nucleosome. The nucleosome octamer includes two copies of each histone H2A, H2B, H3, and H4.
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.
For example, spermatozoa and avian red blood cells have more tightly packed chromatin than most eukaryotic cells, and trypanosomatid protozoa do not condense their chromatin into visible chromosomes at all. Prokaryotic cells have entirely different structures for organizing their DNA (the prokaryotic chromosome equivalent is called a genophore ...
Likewise, a pair of SMC2 and SMC4 acts as the core of the condensin complexes implicated in chromosome condensation. [ 8 ] [ 9 ] SMC2 and SMC4 have the function of DNA repair as well. Condensin I plays a role in single-strained break repair but not in double-strained breaks.