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The genomes of most eukaryotic mitochondria and plastids are in a single circular chromosome, in line with their bacterial ancestor. However, a good number of eukaryotic species do harbor linear Mitochondrial DNA (mtDNA), some even broken into multiple molecules, across a wide variety of taxa: animals (mammals, medusozoans, sponges), fungi (especially yeast), plants, and Alveolatas.
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 ...
Most organisms have the same genomic DNA in every cell; however, only certain genes are active in each cell to allow for cell function and differentiation within the body. [2] gDNA predominantly resides in the cell nucleus packed into dense chromosome structures. Chromatin refers to the combination of DNA and proteins that make up chromosomes.
DNA usually occurs as linear chromosomes in eukaryotes, and circular chromosomes in prokaryotes. The set of chromosomes in a cell makes up its genome; the human genome has approximately 3 billion base pairs of DNA arranged into 46 chromosomes. [96] The information carried by DNA is held in the sequence of pieces of DNA called genes.
The cellular components of prokaryotes are not enclosed in membranes within the cytoplasm, like eukaryotic organelles. Bacteria have microcompartments, quasi-organelles enclosed in protein shells such as encapsulin protein cages, [4] [5] while both bacteria and some archaea have gas vesicles. [6] Prokaryotes have simple cell skeletons.
During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts.
They are simpler and smaller than eukaryotic cells, and lack a nucleus, and other membrane-bound organelles. The DNA of a prokaryotic cell consists of a single circular chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid. Most prokaryotes are the smallest of all organisms, ranging ...
Other eukaryotic chromosomes, i.e., mitochondrial and plasmid-like small chromosomes, are much more variable in number, and there may be thousands of copies per cell. The 23 human chromosome territories during prometaphase in fibroblast cells. Asexually reproducing species have one set of chromosomes that are the same in all body cells. However ...