DNA

• DNA stands for deoxyribose nucleic acid.
• DNA is present in the nucleus of all cells in all living organisms.
• DNA controls all the chemical changes which take place in cells, the type of cell formed, and the type of organism.
• DNA is a very large molecule made up of a long chain of sub-units.
• The sub-units of DNA are called nucleotides.
• Each nucleotide is made up of a sugar called deoxyribose, a phosphate group -PO4 and an organic base.
• Ribose is a sugar, like glucose, but with only five carbon atoms in its molecule.
• Deoxyribose is almost the same but lacks one oxygen atom.
• Both molecules may be represented by the symbol of a pentagon.
• The most common organic bases are Adenine, Thymine, Cytosine and Guanine.
• The deoxyribose, the phosphate and one of the bases combine to form a nucleotide.
• A molecule of DNA is formed by millions of nucleotides joined together in a long chain.
• The sugar-phosphate backbone and the organic bases of DNA form a double helix shape.
• Before the cell divides, the DNA strands unwind and separate.
• Each strand makes a new partner by adding the appropriate nucleotides.
• The result of this process is that there are now two double-stranded DNA molecules in the nucleus.
• This process is called replication.
• Each strand builds its partner by adding the appropriate nucleotides.
• The template strand of DNA is used for the genetic code.
• The complementary strand of DNA is not used.