Download DNA RNA

Chapter #10
10.1 Discovery of DNA
10.2 DNA Structure
10.3 DNA Replication
10.4 Protein Synthesis
Griffith’s Experiments
Griffith’s Experiments (2)
 1928
 A mouse injected w/ both heat killed S
(virulent) and R types can cause
pneumonia
 A HEREDITARY FACTOR must be released
and taken into the R type
 Is this factor protein? DNA? RNA?
Avery’s Experiments
 1940’s
 Wanted to determine if the material that was
transforming was protein, DNA or RNA
 Protease to destroy protein
 Injected w/heat killed S cells and R cells
 Able to transform R to S
 RNase to destroy RNA
 Injected w/heat killed S cells and R cells
 Able to transform R to S
 DNase to destroy DNA
 Injected w/heat killed S cells and R cells
 Not able to transform R to S
Hershey-Chase
Experiment
 1952
 Protein or DNA?
 Little protein found
in viruses; all the
DNA was present
DNA!!!!!
The Structure of DNA
 Sugar-Phosphate Backbone
 Deoxyribose (sugar found in DNA)
 Nitrogen Bases




Adenine
Thymine
Guanine
Cytosine
The Structure of DNA (2)
 Purine
 Double ringed base
 Guanine and Thymine
 Pyrimidine
 Single ringed base
 Cytosine and Adenine
 Purines must pair with pyrimidines so the
helix can be made (it can twist)
DNA
 Deoxyribonucleic acid
 Contains genes that code for proteins
 Involved in heredity
Adenine
 Nitrogen base in both DNA and
RNA
 Purine that pairs with thymine in
DNA and uracil in RNA
Guanine
 Nitrogen base in both DNA and
RNA
 Purine that pairs with cytosine in
both DNA and RNA
Thymine
 Nitrogen base in DNA only
 Pyrimidine that pairs with adenine
Cytosine
 Nitrogen base found in both DNA
and RNA
Deoxyribose
 5 carbon sugar found in DNA
 Makes up the backbone of DNA
(sides of the ladder)
Phosphate Group
 Backbone of DNA
 Alternates with deoxyribose
Hydrogen Bonds
 Bond that joins the nitrogen bases
together
Nucleotide
 Building block of nucleic acids
 Contains…
 5 carbon sugar
 Nitrogen base
 Phosphate group
DNA Carries the Genetic Code
Replication
 Process of duplicating DNA
 Results in 2 DNA molecules (old
and new strands mixed)
 Replication is said to be semiconservative
DNA Helicase
 Enzyme responsible for the untwisting of
DNA
 Starts the replication process
DNA Polymerase
 Enzyme responsible for attaching the
nucleotides in the correct order during
replication.
DNA




Deoxyribose
Double stranded
Thymine
One version
RNA




Ribose
Single stranded
Uracil
3 versions
Sugar-Phosphate backbone
Nucleic Acids Adenine, Guanine, Cytosine
Steps in replication
 DNA helicase unwinds the DNA molecule at
several spots
 Breaks the hydrogen bonds between the bases
 DNA polymerase adds new nucleotides
 2 new strands
 Original strand + new strand = semiconservative
model
Structure of RNA
 Uracil – nitrogen base found only in RNA
(pyrimidine)
 Ribose – 5 carbon sugar found only in
RNA
Types of RNA
 tRNA - transfer
 mRNA - messenger
 rRNA - ribosomal
tRNA
 Used to carry amino acids to codons on
mRNA
 Contains the anticodons on one end and
an amino acid on the other end
mRNA
 Contain codons
 Made through transcription in the
nucleus
 Read by the tRNA during translation in
the ctyoplasm
Transcription Vs. Translation
 Transcription – process of making RNA
from DNA in the nucleus of the cell
 Translation – process of making proteins
 tRNA recognizes codons of the mRNA and
attaches the amino acids in the correct
sequence for the protein that DNA coded
for.
Codon
 Set of 3 bases found on mRNA
 Complementary to the anticodon on the
tRNA
Anticodon
 Set of 3 bases found on a tRNA
molecule
 Recognizes the codon on mRNA during
translation
Amino Acid
 Building block of a protein
 20 different kinds (essential and
nonessential)
Peptide Bond
 Bond that joins amino acids together in
the growing polypeptide chain
Polypeptide
 Made through translation
 Growing chain of amino acids that
transforms into a protein
RNA Polymerase
 Enzyme responsible for attaching RNA
nucleotides in the correct order.
Steps of Transcription (in
the nucleus)
 DNA is the template
 RNA polymerase adds the RNA nucleotides
 Uracil replaces Thymine
 Once transcribed, mRNA leaves the nucleus and
enters the cytoplasm
 Hooks up with a ribosome to begin translation
Steps of Translation
 Ribosome, mRNA and tRNA needed to begin
 Anticodon on tRNA matches with the codon on
mRNA
 Always begins w/ start codon (AUG)
 Adjacent amino acids form peptide bonds
 tRNA keeps adding amino acids until the stop
codon is read
Steps of Translation
 tRNA releases the polypeptide chain (it
will fold and become a functional
protein)
 “naked” tRNA molecules find more
amino acids and the process starts all
over (as certain proteins are needed)