Mitosis (source code)
= Mitosis
{wiki}
<Mitosis> allocates copied <chromosomes> to daughter <cell nuclei>. The <spindle apparatus> aligns <sister chromatids> before separation in <anaphase>.
The copying has already occurred during <S phase>, before <mitosis>. Nuclear <chromosome segregation> and <cytokinesis>, the partition of the <cytoplasm>, are distinct processes: two daughter <cell nuclei> can form inside one undivided <biological cell>.<Biology 2e by Mary Ann Clark and others/The Cell Cycle>[Biology 2e by Mary Ann Clark and others; §10.2, Interphase and The Mitotic Phase; Figure 10.5: replication precedes nuclear division, which can occur without cytokinesis]{ref}
The original cartoon follows a hypothetical <diploid> <animal> <biological cell> with $2n=4$. Its two <homologous chromosome> pairs are $A,a$ and $B,b$; upper- and lower-case letters identify homologues, not dominant and recessive <alleles>. In <prophase> and <metaphase>, each replicated <chromosome> contains two <sister chromatids>: four replicated <chromosomes> contain eight <chromatids>, rather than eight replicated <chromosomes>. The X shape depicts two associated copies, not the shape of every <chromosome> throughout the <cell cycle>.
\Image[/mitosis-animal-chromosome-partition.png]
{title=<Mitosis> partitions replicated <chromosomes>; <cytokinesis> separates the daughters}
{description=Original schematic of a hypothetical $2n=4$ <animal> <biological cell>, drawn with open <mitosis>. Colors and letters follow the four original <chromosomes>; paired strokes represent <sister chromatids>. Every <anaphase> pole and each completed daughter receives $A,a,B,b$. Green lines represent selected <spindle apparatus> <microtubules>; dark dots mark <centromere> regions. The intermediate <prometaphase> is described below. Geometry and arrow spacing are illustrative, not recorded images or elapsed times.}
This open <mitosis> cartoon shows <nuclear envelope> breakdown and reassembly. Closed <mitosis> in some <yeasts> retains the <nuclear envelope> while daughter <chromosomes> separate inside it; the cartoon is therefore not a universal cellular architecture.<The Cell: A Molecular Approach, 2nd edition by Geoffrey M. Cooper>[Chapter 8, The Nucleus during Mitosis, Dissolution of the Nuclear Envelope; Figures 8.29–8.30: open and closed mitosis]{ref}
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