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Double Minute
Double minutes are small fragments of extrachromosomal DNA, which have been observed in a large number of human tumors including breast, lung, ovary, colon, and most notably, neuroblastoma. They are a manifestation of gene amplification as a result of chromothripsis, during the development of tumors, which give the cells selective advantages for growth and survival. This selective advantage is as a result of double minutes frequently harboring amplified oncogenes and genes involved in drug resistance. DMs, like actual chromosomes, are composed of chromatin and replicate in the nucleus of the cell during cell division. Unlike typical chromosomes, they are composed of circular fragments of DNA, up to only a few million base pairs in size, and contain no centromere or telomere. Further to this, they often lack key regulatory elements, allowing genes to be constitutively expressed. The term ecDNA may be used to refer to DMs in a more general manner. Formation The most commonl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extrachromosomal DNA
Extrachromosomal DNA (abbreviated ecDNA) is any DNA that is found off the chromosomes, either inside or outside the nucleus of a cell. Most DNA in an individual genome is found in chromosomes contained in the nucleus. Multiple forms of extrachromosomal DNA exist, and, while some of these serve important biological functions, they can also play a role in diseases, such as ecDNA in cancer. In prokaryotes, nonviral extrachromosomal DNA is primarily found in plasmids, whereas, in eukaryotes extrachromosomal DNA is primarily found in organelles. Mitochondrial DNA is a main source of this extrachromosomal DNA in eukaryotes. The fact that this organelle contains its own DNA supports the hypothesis that mitochondria originated as bacterial cells engulfed by ancestral eukaryotic cells. Extrachromosomal DNA are often used in research of replication because they are easy to identify and isolate. Although extrachromosomal circular DNA (eccDNA) is found in normal eukaryotic cells, extrachro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
