Concept 49 - Concept 16.3 A chromosome consists of a DNA...

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Concept 16.3 A chromosome consists of a DNA molecule packed together with proteins. Most bacteria have a single, circular, double-stranded DNA molecule, associated with a small amount of protein. o The bacterial chromosome is very different from a eukaryote chromosome, which is a linear DNA molecule associated with a large amount of protein The chromosomal DNA of E. coli consists of about 4.6 million nucleotide pairs, representing about 4,400 genes. o Stretched out, this DNA would be about a millimeter long, 500 times longer than an E. coli cell. A bacterium has a dense region of DNA called the nucleoid. o Within the nucleoid, proteins cause the chromosome to tightly coil and “supercoil,” densely packing it so that it fills only part of the cell. Each eukaryotic chromosome contains a single linear DNA double helix that, in humans, has an average of about 1.5 10 8 nucleotide pairs. o
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