1. Chapter 10

2.  Deoxyribonucleic acid  Primary function:  To store and transmit the genetic information that tells cells which proteins to make and when to make them.  Proteins  Form the structural units of cells  Help control chemical processes within cells.

3.  Made up of repeating subunits – nucleotides.  Each DNA contains two long chains of nucleotides.  DNA nucleotide has three parts:  Deoxyribose – sugar molecule  Phosphate group  Nitrogen-containing base – molecule that contains nitrogen; four different kinds.

4.  AKA nitrogenous bases  Four kinds:  1. adenine (A)  2. guanine (G)  3. cytosine (C)  4. thymine (T)  A and T always bond together.  C and G always bond together.

5.  1953: James Watson & Frances Crick suggested model for DNA structure.  Proposed that DNA is composed of two nucleotide chains that wrap around each other to form a double spiral  Like a spiral staircase.  Called this shape the double helix.

6.  Cytosine and guanine always pair  Adenine and thymine always pair  These pairs of bases are called complementary base pairs.  Base pairs are connected to each other by hydrogen bonds.  C and G form 3 hydrogen bonds.  A and T form 2 hydrogen bonds.

8.  The process of copying DNA in a cell – replication.  The two nucleotide chains separate by unwinding  Each chain is template for new nucleotide chain  Enzymes called helicases separate the two chains.  Helicases move along the DNA molecule and break the hydrogen bonds between the nitrogenous bases, separating the chains.  Then enzymes called DNA polymerases bind to the separated chains of DNA.

9.  As the polymerases move along the separated chains, new chains of DNA are assembled using nucleotides that are complementary to the existing DNA chains.  Complementary nature is as follows:  One side of the DNA has A-T-C-C-A-G  Compliment would be: T-A-G-G-T-C  When replication is finished two new exact copies of the original DNA molecule are produced  The cell is ready to undergo cell division.

11.  DNA replication occurs with a high degree of accuracy.  Only about 1 error in every 10,000 paired nucleotides.  A change in the nucleotide sequence is called a mutation.  Can have serious effects on new cells.