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The organization of chromosomes into distinct regions within the nucleus was first proposed in 1885 by Carl Rabl.Later in 1909, with the help of the microscopy technology at the time, Theodor Boveri coined the termed chromosome territories after observing that chromosomes occupy individually distinct nuclear regions. [6]
The vast expansion of the genome with noncoding and repetitive DNA in higher eukaryotes implies more extensive epigenetic silencing mechanisms. Studies of the genomic organization are thought to be the future of genomic medicine, which will provide the opportunity for personalized prognoses in clinics. [4]
In nature, DNA can form three structures, A-, B-, and Z-DNA. A- and B-DNA are very similar, forming right-handed helices, whereas Z-DNA is a left-handed helix with a zig-zag phosphate backbone. Z-DNA is thought to play a specific role in chromatin structure and transcription because of the properties of the junction between B- and Z-DNA.
Location of eukaryote nuclear DNA within the 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]
Some types of non-coding DNA are genetic "switches" that do not encode proteins, but do regulate when and where genes are expressed (called enhancers). [30] Regulatory sequences have been known since the late 1960s. [31] The first identification of regulatory sequences in the human genome relied on recombinant DNA technology. [32]
Archaea and most bacteria have a single circular chromosome, [22] however, some bacterial species have linear or multiple chromosomes. [23] [24] If the DNA is replicated faster than the bacterial cells divide, multiple copies of the chromosome can be present in a single cell, and if the cells divide faster than the DNA can be replicated ...
Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms. The chemical DNA was discovered in 1869, but its role in genetic inheritance was not demonstrated until 1943. The DNA segments that carry this genetic information are called genes.
For this reason they are known as the ‘scaffold’ of chromosomes. [1] Three protein groups have been identified as the main components of the scaffold: DNA topoisomerase IIα, condensins, and the KIF4A kinesin. When these proteins are removed, the chromosome shape does not appear and the chromatin fibers spread out. [1]