Upload
carol-wiggins
View
226
Download
1
Embed Size (px)
DESCRIPTION
They all share a universal genetic code. What do all of these organisms have in common? The answer – Universal genetic code They all share a universal genetic code.
Citation preview
DNA and RNA
• What do all of these organisms have in common?
They all share a universal genetic code.
How do we know that all of our genetic information comes from DNA?
Thanks to many scientists and many experiments over the last ≈ 90 years.
Let’s take a look…….
Who helped?• In 1928: Griffith accidentally
discovered a process called Transformation that turned non-deadly bacteria into deadly pneumonia causing bacteria.
• In 1944: Avery, McCarty, and MacLeodRepeated Griffith’s Experiment
• Discovered DNA was the transformation factor.
• In 1952: Hershey-Chase experimented with bacteria and bacteriophages. Showed DNA was what entered the bacteria and caused disease.
Now we know!
DNA carries the genetic code!
But, how do we know how it works?
How did DNA:
DNA’s Structure was the key!
2. Duplicate itself easily?
1. Store information?
The Race to Discover DNA’s Structure
1950Chargaff’s Rule: Equal amounts of Adenine and Thymine, and equal amounts of Guanine and Cytosine
Erwin Chargaff
Why do you think the bases match up
this way?
Purine + Purine = Too wide
Pyrimidine + Pyrimidine = Too Narrow
Purine + Pyrimidine = Perfect Fit from X-ray data
The Race to Discover DNA’s Structure
Maurice Wilkins
Rosalind Franklin
X-Ray diffraction image of DNA taken by Franklin in
1951
The Race to Discover DNA’s Structure
James Watson Francis Crick
1953Compiled data from previous scientists to build a double-helical model of DNA
DNA and RNA are Nucleic Acids• What is a nucleic acid?
• Nucleic acids are one of the major organic biomolecules.
Nucleic Acids• They contain C, H,
N, O, P• They are made of
nucleotide monomers
• They store information• The instructions makes
proteins
• Examples: DNA & RNA
sugar
phosphate
nitrogen base
DNA Structure• What does DNA stand for?• What is the monomer for nucleic acids?• What is the structure of this monomer?
nucleotide
N base
PO4
SugarSugar
PO4
N baseThe numbers are the positions of the carbons on the sugar.
(the 3’ end)
5
4
3 2
1
(the 5’ end)
DeoxyriboNucleic Acid
A DNA NUCLEOTIDE
H
H2
H H
H3
HH H
H
H
O
O
O
C C
C
N
N
PO
O
O
C
C
C C
C
O
OO
C
C
1.
2.
3.
1.
2.
3.1. Phosphate Group2. 5-Carbon Sugar (Dexoyribose)3. Nitrogen Base
1. Phosphate Group
2. 5-Carbon Sugar(Dexoyribose)
3. Nitrogen Base
DNA Nucleotides• There are four nitrogen bases making up four
different nucleotides.
Adenine
Guanine
Thymine
CytosinePyrimidines
PurinesA
C
G
T
N base
Chargaff’s Base Pair Rules• Adenine always bonds with thymine.
• Guanine always bonds with Cytosine.
The lines between the bases represent hydrogen bonds
A
CG
T
C
G
A
A
T
G
Nucleotide PS
N-b
Pairing DNA Nucleotides• What is a nucleotide?
Rule
A to T
C to G
What is the base pairing rule?What would be the complementary nucleotide pairing?
3’End
3’End 5’End
5’End
DNA
DOUB
LE H
ELIX
ladder shaped molecule
Purpose of DNA• DNA contains our genetic code which codes
for proteins.• It is our “blueprint”…all cells have the same
blueprint, but only certain parts are looked at when building different cells
What is RNA?• RNA stands for
RiboNucleic Acid• DNA must have a “helper”
molecule. (DNA is too fat)
• RNA is a single stranded nucleic acid
• made up of monomers called nucleotides
sugar
phosphate
nitrogen base
A
B
C
RNA Nucleotides• A - Sugar (ribose)• B - Phosphate• C - Nitrogen base
sugar
phosphate
nitrogen base
Phosphate Group
Nitrogen Base
Sugar
(ribose)
RNA• Identify the parts of the RNA strand.
• Adenine bonds with Uracil.
• Guanine bonds with Cytosine.
A
CG
U
Rules for Base Pairing
DNA makes RNA• C = G
• A = U
3’ DNA strand
5’ DNA strandRNA strand
C
A
T
G
G
U
C
A
What is the function of RNA?• Carries the coded “message” of DNA.• Translates the “message” into proteins
• 3 Types of RNA• Messenger RNA (mRNA)• Transfer RNA (tRNA)• Ribosomal RNA (rRNA)
DNA RNASugar is deoxyribose
Sugar is ribose
Adenine base is present
Cytosine base is present
√√
√ √√ √
Comparing DNA & RNA
DNA RNAGuanine base is present
Thymine base is present
Uracil base is present
Shape is double helix
√ √
√√
√
Comparing DNA & RNA
DNA RNAShape is single stranded
Located in nucleus
Located in cytoplasm
Stores genetic information
√√ √
√
√
Comparing DNA & RNA
DNA RNAFunctions in protein synthesis
Composed of nucleotides
Instructions (template) for synthesis of proteinsTranscribes and Translates the templateMore than one type
√ √
√ √
√
√
√
Comparing DNA & RNA