DNARNA-Part4

DNARNA-Part4 - DNA in eukaryotic cells is associated with...

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Unformatted text preview: DNA in eukaryotic cells is associated with various proteins to form chromatin . Prior to cell division (metaphase) chromatin becomes organized into compact structures called chromosomes Early stages of DNA packing lead to formation of 30-nm fibers Naked DNA is associated with a class of highly basic proteins called histones In mammals, genes for specific proteins and sequences that control gene expression represent only 2-4% of the entire DNA sequence. No specific function has been assigned for the majority of the noncoding DNA (junk DNA) and it is believed that up to 70-80% of the human DNA is of retroviral origin. Most eukaryotic genes are interrupted by noncoding intervening nucleotide sequences, called introns. The sequences in the gene that are expressed, either in the final RNA product (mature RNA) or as a protein, are termed exons. The introns are removed during the processing of the RNA transcript, and the remaining exons are ligated together. This tailoring of the original transcript is referred to as splicing . Central...
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DNARNA-Part4 - DNA in eukaryotic cells is associated with...

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