Download S-strain (virulent)

Nucleic Acids and Protein Synthesis
Griffith took the 1st steps in answering whether
genes are made of DNA or Protein.
Used bacteria to help solve this problem.
S-strain (virulent) - Coated with mucus and
caused pneumonia
R-strain (avirulent) - no mucus and did not
cause pneumonia
Griffith’s Experiment
These results led Griffith to believe that some
material from the S-strain was transferred to the
R-strain, which converted the R-strain to s-strain.
Transformation - the process during which bacteria
are changed by absorbing genetic material from an
outside source.
Griffith was still not sure whether it was DNA or
Protein being transferred.
Chase and Hershey used bacteriophages
(phages) to prove whether protein or DNA is the
genetic material.
The Experiment
1. Radioactive DNA was put in one group of phages and
radioactive protein was put into another group of
phages.
2. The phages were used to infect the bacteria.
3. Radioactivity was only found in bacteria infected by
DNA.
4. DNA is the genetic material.
Chargaff’s Rule
The amount of adenine in DNA is always equal to the
amount of thymine.
%A = %T
The amount of cytosine in DNA is always equal to the
amount of guanine.
%C = %G
•Discovered by Watson and Crick
•Consist of long strands of nucleotides
•Deoxyribose
•Phosphate group
•Nitrogenous bases
Adenine
Guanine
Cytosine
Thymine
The nitrogenous bases are divided into two groups.
Purines - include adenine
and guanine.
They have two rings.
Pyrimidines - include
cytosine and thymine.
They are smaller and
have only one
ring.
Has a sugar phosphate backbone on
the outside (sides of the ladder)
Bases face inward toward the
center and meet each other in pairs
(rungs of the ladder). The bases
are held together by hydrogen
bonds.
Adenine - Thymine
Cytosine - Guanine
double bond
triple bond
The process by which DNA makes copies of itself
(Interphase of Cell Division)
1. Double helix unwinds
2. Hydrogen bonds are broken
3. The two strands break apart, like a zipper
4. New nucleotides begin to attach to the original DNA
5. This will form two new DNA molecules
This is semiconservative replication, because each new
strand is half comprised of molecules from the old strand.
DNA is a code (set of blueprints) for making protein.
Protein synthesis is the process that manufactures proteins.
RNA
Nucleic Acid
•Single stranded
•4 Bases
Adenine
Cytosine
•Ribose sugar
Guanine
Uracil
Messenger RNA (mRNA)
Carries the coded instructions for protein
synthesis from the DNA in the nucleus to the
ribosome.
Transfer RNA (tRNA)
Brings amino acids to the ribosome in the
correct order so that they can be built into the
new protein.
Ribosomal RNA (rRNA)
Make up the structure of a ribosome, along with
several proteins.