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Organization of DNA - Unknown Function Less than 5 of...

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Organization of DNA Chromosome Structure Chromosomes are structures composed of condensed DNA and associated proteins. When DNA condenses, the molecule becomes wrapped around proteins called histones . The histones are then arranged in a coiled pattern to produce a larger fiber. This larger fiber is further compacted by looping to produce looped domains. The looped domains are coiled and compacted to produce chromosomes. Heterochromatin and Euchromatin Chromatin is DNA and its associated protein. Heterochromatin is DNA that is coiled and condensed. In this state, it is not transcribed. Euchromatin is less condensed and is actively transcribed. During interphase, looped domains may be attached to protein supporting structures on the inside of the nuclear membrane. Some of the DNA is coiled and compacted but other parts are not.
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Unformatted text preview: Unknown Function Less than 5% of eukaryotic DNA functions to code for proteins. Approximately 1.5% of human DNA codes for protein. The function of the remaining DNA is not known but perhaps much of it has no function. In the past, noncoding DNA was sometimes called "junk DNA" because its function was not well understood. Some parts of the DNA contain more genes than other parts. The gene-rich portions are rich in G and C while the noncoding DNA is rich in A and T. The light bands on chromosomes are gene-rich regions. Highly Repetitive Sequences 10-25% of eukaryotic DNA consists of sequences of 5 to 10 nucleotides repeated 100,000 to 1,000,000 times. This type of DNA probably does not code for proteins. A large proportion of this type of DNA is found at the tips of the chromosomes and at the centromere....
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