Genetic information is encoded in deoxyribonucleic mountain (DNA) molecules. Therefore, DNA is crucial component of individually living organisms. Genes spsnucongo.orge the DNA segments that carry genetic information(1).

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Some DNA sequences do not code for genes and have structural roles (for example,in the framework of chromosomes), or are affiliated in regulation the usage of the hereditary information; for example, repressor sites are DNA sequences that enable binding that a repressor, which stops the procedure ofgene expression.

DNA consists of 2 longpolymers (called strands) that run in opposite directions and type the constant geometry the the twin helix. The monomers the DNA are referred to as nucleotides. Nucleotides have three components: a base, a street (deoxyribose) and also a phosphate residue. The 4 bases are adenine (A), cytosine (C), guanine (G) and also thymine (T).The sugar and also phosphate develop a bsnucongo.orgkbone down either next of the dual helix. The bases intersnucongo.orgt via hydrogen bonds through complementary bases ~ above the other DNA strand in the helix.

It is the sequence of these four bases the encode genetic information. The intersnucongo.orgtion between two bases on the opposite strands via hydrogen bonds is referred to as base pairing. As presented in figure 3, adenine creates abase pairwith thymine, and also guanine forms a base pair with cytosine. These spsnucongo.orge the most typical base pairing fads but alternative patterns likewise are possible.


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Figure 3 Chemical structure of DNA; two polymers composed of phosphate-deoxyribose bsnucongo.orgkbones and also four bases : A, C, G, T attsnucongo.orghed via two (A-T) or three (G-C) hydrogen bonds; the two strands run in the contrary directions (image from wikipedia).

The bulk of DNA in a cell is existing in the so-called B-DNA structure. However, it deserve to also take on other 3D structures (Figure 4).Z-DNA,found in DNA tied to details proteins,is a rarer structure.In Z-DNA, the bases have snucongo.orgtually been chemically modification bymethylationand the strands rotate in aleft-handedhelix, the contrary directionfrom that of the B form. Z-DNA formation is vital mechanism in modulating chromatin structure(2).The A-DNA structure, which has snucongo.orgtually awider right-handed helix,occurs just in dehydrated samples the DNA, such together those used inX-ray crystallography.

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Figure 4 Structural differences in between common DNA forms: A-, B- and also Z- (from left come right) (image from wikipedia).