DNA is of the nucleic acids, information-containing molecules in the cell (ribonucleic acid, or RNA, is the other nucleic acid). DNA is present in the nucleus of every human cell. (See the sidebar at the bottom of the page for more about RNA & different types of cells).
The information in DNA : Guides the cell (along with RNA) in making new proteins that choose all of our biological traits
gets passed (copied) from generation to the next
The key to all of these functions is present in the molecular structure of DNA, as described by Watson & Crick.
Although it may look complicated, the DNA in a cell is a pattern made up of different parts called nucleotides. Imagine a set of blocks that has only shapes, or an alphabet that has only letters. DNA is a long string of these blocks or letters. Each nucleotide consists of a sugar (deoxyribose) bound on side to a phosphate group & bound on the other side to a nitrogenous base.
There's classes of nitrogen bases called purines (double-ringed structures) & pyrimidines (single-ringed structures). The bases in DNA's alphabet are :
adenine (A) - a purine
cytosine(C) - a pyrimidine
guanine (G) - a purine
thymine (T) - a pyrimidine
Watson & Crick discovered that DNA had sides, or strands, & that these strands were crooked together like a crooked ladder -- the double helix. The sides of the ladder comprise the sugar-phosphate portions of adjoining nucleotides bonded together. The phosphate of nucleotide is covalently bound (a bond in which or more pairs of electrons are shared by atoms) to the sugar of the next nucleotide. The hydrogen bonds between phosphates cause the DNA strand to twist. The nitrogenous bases point inward on the ladder & form pairs with bases on the other side, like rungs. Each base pair is formed from complementary nucleotides (purine with pyrimidine) bound together by hydrogen bonds. The base pairs in DNA are adenine with thymine & cytosine with guanine.
gets passed (copied) from generation to the next
The key to all of these functions is present in the molecular structure of DNA, as described by Watson & Crick.
Although it may look complicated, the DNA in a cell is a pattern made up of different parts called nucleotides. Imagine a set of blocks that has only shapes, or an alphabet that has only letters. DNA is a long string of these blocks or letters. Each nucleotide consists of a sugar (deoxyribose) bound on side to a phosphate group & bound on the other side to a nitrogenous base.
There's classes of nitrogen bases called purines (double-ringed structures) & pyrimidines (single-ringed structures). The bases in DNA's alphabet are :
adenine (A) - a purine
cytosine(C) - a pyrimidine
guanine (G) - a purine
thymine (T) - a pyrimidine
Watson & Crick discovered that DNA had sides, or strands, & that these strands were crooked together like a crooked ladder -- the double helix. The sides of the ladder comprise the sugar-phosphate portions of adjoining nucleotides bonded together. The phosphate of nucleotide is covalently bound (a bond in which or more pairs of electrons are shared by atoms) to the sugar of the next nucleotide. The hydrogen bonds between phosphates cause the DNA strand to twist. The nitrogenous bases point inward on the ladder & form pairs with bases on the other side, like rungs. Each base pair is formed from complementary nucleotides (purine with pyrimidine) bound together by hydrogen bonds. The base pairs in DNA are adenine with thymine & cytosine with guanine.
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