polynucleotide chain

Polynucleotide chainclick for a larger image
Fig. 257 Polynucleotide chain . General structure.P = phosphate, S = ribose or deoxyribose sugar,B = one of four bases.

polynucleotide chain

a sequence of NUCLEOTIDES joined together. RNA generally consists of one polynucleotide chain, while DNA may consist of one chain (single-stranded DNA), or two chains bonded between the bases in a system of complementary pairing: adenine with thymine, guanine with cytosine (double-stranded DNA). The sequence of bases along the chain acts as a GENETIC CODE for the sequence of AMINO ACIDS of PROTEINS. Polynucleotide chains show polarity based upon the position of the bonds in relation to the sugar component. One end of the chain will terminate at the 3′ position, the other at the 5′ position. See Fig. 257 . See also END. The two chains of DNA show opposite polarities (see Fig. 135).