Genetic Control
DNA and RNA are polynucleotides, made up of a long chains of nucleotides. A nucleotide contains a pentose sugar, a phosphate group, and a nitrogen-containing base. A DNA molecule consists of two polynucleotide chains, linked by hydrogen bonds between bases. Adenine always pairs with thymine and cytosine with guanine. RNA, which comes in several different forms, has only one polynucleotide chain, although this may be twisted back on itself, as in tRNA. In RNA, the base thymine is replaced by uracil.
DNA molecules replicate during interphase. The hydrogen bonds between the bases break, allowing free nucleotide to fall into position opposite their complementary ones on each strand of the original DNA molecule. Adjacent nucleotides are then linked, through their phosphates and sugars, to form new strands. Two complete new molecules are thus formed from one old one, each new molecule containing on old strand and one new.
The sequence of bases (or nucleotides) on a DNA molecule codes for the sequence of amino acids in a protein (or polypeptide). Each amino acid is coded for by three bases. A length of DNA coding for one complete protein or polypeptide is a gene.
DNA molecules replicate during interphase. The hydrogen bonds between the bases break, allowing free nucleotide to fall into position opposite their complementary ones on each strand of the original DNA molecule. Adjacent nucleotides are then linked, through their phosphates and sugars, to form new strands. Two complete new molecules are thus formed from one old one, each new molecule containing on old strand and one new.
The sequence of bases (or nucleotides) on a DNA molecule codes for the sequence of amino acids in a protein (or polypeptide). Each amino acid is coded for by three bases. A length of DNA coding for one complete protein or polypeptide is a gene.