Chromatin undergoes few structural changes throughout a cell cycle. Histone proteins are the general packer and coordinator of chromatin and can be altered by numerous post-translational changes to alter chromatin packing. Most of the modifications take place on the histone tail. The consequences in terms of chromatin availability and compaction depend both on the amino-acid that is altered and the kind of modification. For instance, Histone acetylation results in loosening and rising accessibility of chromatin for duplication and transcription. Lysine tri-methylation may either be associated with transcriptional activity (tri-methylation of Lysine 4histone H3) or transcriptional suppression and chromatin compaction (tri-methylation of Lysine 9 or 27histone H3). Numerous studies suggested that different modifications could happen at the same time. For instance, it was suggested that a bivalent structure (with tri-methylation of both histone H3 on Lysine 4 and 27) was involved in mammalian primary development.
The basic recurrence component of chromatin is the nucleosome, connected by sections of linker DNA, a far shorter arrangement than pure DNA in the mixture.
In prophase of mitosis, chromatin fibers turn into coiled chromosomes. Each duplicated chromosome contains two chromatids combined or linked at a centromere.
Throughout metaphase, the chromatin develops extremely condensed. The chromosomes line up at the metaphase plate.
Throughout anaphase, the paired chromosomes or sister chromatids divide and are pulled by the spindle microtubules to opposite ends of the cell.
During telophase, every new daughter chromosome is divided into its own nucleus. Chromatin fibers uncoil and develop less condensed. Following cytokinesis, two genetically equal daughter cells are formed. Every cell has a similar number of chromosomes. The chromosomes continue to uncoil and elongate creating chromatin.
People often have trouble in distinguishing the transformation between the word chromatin, and chromatid chromosome. While all three structures are made up of DNA and can be found within the nucleus, each is exclusively defined.