3/9/2023 0 Comments Groove lifeThese two long strands coil around each other, in the shape of a double helix. ĭNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. Chromosome 1 is the largest human chromosome with approximately 220 million base pairs, and would be 85 mm long if straightened. Although each individual nucleotide is very small, a DNA polymer can be very long and may contain hundreds of millions of nucleotides, such as in chromosome 1. According to another study, when measured in a different solution, the DNA chain measured 22–26 Å (2.2–2.6 nm) wide, and one nucleotide unit measured 3.3 Å (0.33 nm) long. The pair of chains have a radius of 10 Å (1.0 nm). Both chains are coiled around the same axis, and have the same pitch of 34 ångströms (3.4 nm). In all species it is composed of two helical chains, bound to each other by hydrogen bonds. The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. Each end of the double helix has an exposed 5' phosphate on one strand and an exposed 3' hydroxyl group (-OH) on the other.ĭNA is a long polymer made from repeating units called nucleotides, each of which is usually symbolized by a single letter: either A, T, C, or G.
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