Polynukleotidiketjut

Polynukleotidiketjut, often referred to as polynucleotide chains, are essential molecules in biology. They are long chains composed of repeating units called nucleotides. Each nucleotide consists of three components: a phosphate group, a pentose sugar (either deoxyribose or ribose), and a nitrogenous base. The specific sequence of these nitrogenous bases within the polynucleotide chain carries the genetic information.

In DNA (deoxyribonucleic acid), the sugar is deoxyribose, and the bases are adenine (A), guanine (G), cytosine (C), and thymine (T). DNA typically exists as a double helix, with two polynucleotide chains wound around each other. The bases on one chain pair specifically with bases on the other: A with T, and G with C, through hydrogen bonds. This complementary base pairing is crucial for DNA replication and transcription.

RNA (ribonucleic acid) is similar but differs in several ways. The sugar in RNA is ribose, and uracil (U) replaces thymine. RNA is usually single-stranded, though it can fold into complex three-dimensional structures. There are several types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), each playing distinct roles in protein synthesis and gene regulation. The order of nucleotides in a polynucleotide chain dictates the sequence of amino acids in proteins, thus influencing an organism's traits.