Nucleic Acids DNA & RNA

Where did we find Genes and who Discovered Them?  In 1928 a man named Frederick Griffith was trying to figure out how bacteria made people sick. –What caused pneumonia  Griffith’s Experiment was the key in discovering Genes.

Griffith’s Experiment  Grew 2 strains of bacteria: –Strain 1 –smooth colonies (disease) –Strain 2 –rough colonies (harmless)  Mice injected with the smooth bacteria got pneumonia and died.  Mice injected with the rough bacteria did not get sick at all.  Griffith wondered if maybe the bacteria that was lethal (smooth) produced a poison.

Griffith’s Experiment Continued  To find out if the disease causing bacteria (smooth) made a poison he took some of it, heated it, and injected it into mice.  So what do you think happened?

Griffith’s Experiment Continued  That is right all the mice survived!!  So, the bacteria was not making a chemical poison that was causing the mice to die, so what was?  He did a second experiment…..

Griffith’s Second Experiment  This time he took the heat killed disease causing bacteria (smooth) and mixed it with the live harmless bacteria (rough). –Neither should make the mice sick.  So what do you think happened to the mice this time?

Griffith’s Second Experiment  Many of the mice developed pneumonia and died. –Their lungs were filled with the disease causing bacteria.  So how did this happen? If the disease causing bacteria was heated and killed how did it make the mice sick? –The heat killed disease causing bacteria passed their information to the live harmless strain in a process known as Transformation.

Transformation  The process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria.

Griffith’s Conclusion  Some information from the heat killed disease causing bacteria (smooth) were transferred into the harmless bacteria (rough).  And thus Genes were discovered….

Avery and DNA  In 1944 Oswald Avery decided to take Griffith’s experiment one step farther.  They added an enzyme that breaks down DNA. They then did Griffith’s experiment and this time the mouse did not die. –This experiment proved that the information was being carried by genes, and that those genes are made of DNA.

The Components and Structure of DNA  DNA is a long molecule made up of nucleotides. –Nucleotide:  5 carbon sugar (Deoxyribose)  Nitrogen base  Phosphate group  DNA is made up of 4 kinds of nitrogen bases……

Kinds of Nitrogen Bases  Adenine and Guanine: Purines –Purine bases have 2 ring structures  Cystosine and Thymine: Pyrimidines –Pyrimidine bases only have 1 ring structures

The Components and Structure of DNA Continued  The backbone of a DNA chain is made up of the sugar and phosphate groups of each nucleotide. Sugar and Phosphate Back Bone

Chromosomes and DNA  Where in our bodies do we find our DNA? –Inside of the nucleus.  In the nucleus there are chromosomes which store our DNA. DNA ChromosomeCell Nucleus

Chromosomes Structure  Each chromosome has both DNA and proteins in it. –Chromatin: DNA coiled or wrapped around a histone (protein).  Many histones packed together are called a nucleosome.  Basically a chromosome is made up of DNA wrapped around proteins, coiled together to form nucleosomes that coil up into supercoils called a CHROMOSOME.

The structure of a Chromosome DNA Double Helix Histones Nucleosomes Supercoils Chromosome