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An acentric chromosome is fragment of a chromosome that lacks a centromere. Since centromeres are the attachment point for spindle fibers in cell division, acentric fragments are not evenly distributed to daughter cells during cell division. As a result, a daughter cell will lack the acentric fragment and deleterious consequences could occur.
During metaphase, the kinetochore microtubules extending from each centrosome connect to the centromeres of the chromosomes. Next, during anaphase, the kinetochore microtubules pull the sister chromatids apart into individual chromosomes and pull them towards the centrosomes, located at opposite ends of the cell. This allows the cell to divide ...
Chromatin is a complex of DNA and protein found in eukaryotic cells. [1] The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in reinforcing the DNA during cell division , preventing DNA damage , and regulating gene expression ...
Chromatin contains the vast majority of the DNA in an organism, but a small amount inherited maternally can be found in the mitochondria. It is present in most cells, with a few exceptions, for example, red blood cells. Histones are responsible for the first and most basic unit of chromosome organization, the nucleosome.
In general, each centriole of the centrosome is based on a nine-triplet microtubule assembled in a cartwheel structure, and contains centrin, cenexin and tektin. [10] In many cell types, the centrosome is replaced by a cilium during cellular differentiation. However, once the cell starts to divide, the cilium is replaced again by the centrosome ...
However, the two centrioles are of different ages. This is because one centriole originates from the mother cell while the other is replicated from the mother centriole during the cell cycle. It is possible to distinguish between the two preexisting centrioles because the mother and daughter centriole differ in both shape and function. [5] For ...
Bottom: Two tomato SCs with the chromatin removed, allowing kinetochores ("ball-like" structures) at centromeres to be revealed. The synaptonemal complex ( SC ) is a protein structure that forms between homologous chromosomes (two pairs of sister chromatids ) during meiosis and is thought to mediate synapsis and recombination during prophase I ...
Euchromatin (also called "open chromatin") is a lightly packed form of chromatin (DNA, RNA, and protein) that is enriched in genes, and is often (but not always) under active transcription. Euchromatin stands in contrast to heterochromatin , which is tightly packed and less accessible for transcription. 92% of the human genome is euchromatic.