University:
Sam Houston State University
Course:
BIOL 1406 | General Biology I
Academic year:

2020
Views:

139

Pages:

12
Author:

StellarStrategist

DNA DNA stands for deoxyribose nucleic acid This chemical substance is present in the nucleus of all cells in all living organisms DNA controls all the chemical changes which take place in cells The kind of cell which is formed, (muscle, blood, nerve etc) is controlled by DNA The kind of organism which is produced (buttercup, giraffe, herring, human etc) is controlled by DNA DNA molecule DNA is a very large molecule made up of a long chain of sub-units The sub-units are called nucleotides Each nucleotide is made up of a sugar called deoxyribose a phosphate group -PO4 and an organic base Ribose & deoxyribose 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 The bases The most common organic bases are Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Nucleotides The deoxyribose, the phosphate and one of the bases Combine to form a nucleotide PO4 adenine deoxyribose Joined nucleotides PO4 A molecule of DNA is formed by millions of nucleotides joined together in a long chain PO4 PO4 PO4 sugar-phosphate backbone + bases In fact, the DNA usually consists of a double strand of nucleotides The sugar-phosphate chains are on the outside and the strands are held together by chemical bonds between the bases 2-stranded DNA PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 Bonding 1 The bases always pair up in the same way Adenine forms a bond with Thymine Adenine Thymine and Cytosine bonds with Guanine Cytosine Guanine Bonding 2 PO4 PO4 adenine thymine PO4 PO4 cytosine guanine PO4 PO4 PO4 PO4 Pairing up PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4 PO4