What is DNA?
Where do we find DNA? In the nucleus
What the heck is it?
Why is it soooooooooo important?
Hint… It’s SUPER IMPORTANT and Mz. C. will be mentioning it over and over and over and… you get the picture!
NucleusChromosome
DNA
Nucleic Acid
Nucleotide
Cell
What do ALL of these organisms have in common?
WE all share a universal genetic code: DNA
How do we know what DNA looks like????
•Rosalind Franklin•Chemist…•Used X-Rays and was able to get two photos of crystallized DNA•Watson and Crick used the X-ray data Franklin obtained to figure out the 3-D structure of DNA •Died before she was 38... (due to Cancer caused by Radiation Poisoning)
Watson & Crick•1953•Watson & Crick used Rosalind's X-Rays to figure out the structure of DNA…•(Did they give her any credit??? NAH… not until later!)
What they “Announced”
•Using Rosalind X-Rays, Watson & Crick determined that phosphates and sugars were on the “outside” of the DNA molecule and nitrogen bases were on the “inside”
•They also figured out that DNA is a double helix…
•Rosalind figured out that DNA was in a helical shape… but… didn’t get any further details•What’s a helical shape? Let’s talk helicopters… and screws…!
Helix = Spiral
Helic-opter…
Helical screw…Helical spring…
Helical staircase…
Helical drill…
DNA
Purpose of DNADNA is one of “THE BIG FOUR” Organic Macro-molecules (a Nucleic Acid)Deoxyribonucleic Acid
Why do we have DNA?It is our genetic information
• The “code” for all of our traits/characteristics!
It gives each cell it’s “instructions”
Nucleic Acids…
2 Types:DNA & RNA
Nucleic Acid is a PolymerNucleotides are the
monomers
Stores genetic information (genes)
Gives instructions to make proteinsOne gene=One protein
sugar
phosphate
nitrogen base
What is a 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 Group
2. 5-Carbon Ribose Sugar
3. Nitrogen Base
Three “Similar” Parts
One phosphate groupBonded to
One sugar (ribose)To make the “side” of the ladder
One nitrogen baseMakes the “rungs” (steps) of the
ladder•There are different Nitrogen bases
• DNA & Genes
Different Nitrogen BasesThere are four nitrogen bases in DNA (making up four different nucleotides)
Adenine
Guanine
Thymine
Cytosine
A
C
G
T
Nucleotide Bonding
Nucleotides are bonded together in alternating sugar and phosphate groups •The “Backbone”
This creates a long chain with nitrogen bases sticking off of the side
Making the DNA Ladder
• Two chains line up next to each other...
• The Nitrogen bases bond together in the center to hold the two chains together like a “zipper”• The bases are held by Hydrogen
bonds The Nitrogen bases only bond in
“Complementary Pairs”!
DNA: Double Stranded (Helix)
• The Nitrogen bases bond in the center of the “Ladder”
• The ladder then “twists” into a helix
• The tighter it “twists”, the more “condensed” it becomesWhich means it is more
dense and compact
DN
A D
OU
BL
E H
EL
IX
ladder shaped molecule
Erwin Chargaff
Chargaff discovered that DNA contains the same amount of adenosine as thymine (A-T) and the same amount of cytosine as guanine (C-G).
A AA AA A
AT
T
T
T TTT
CCC G G
G
ALL THUGS CARRY GUNS!
Chargaff’s Base Pair RulesAdenine always bonds with Thymine. A = T
A
CG
T
DNA: All Thugs Carry Guns
Cytosine always bonds with Guanine. C = G
Nucleotide
PS
N-b
Pairing DNA NucleotidesWhat is a nucleotide?
Rule:
A with T
C with G
What is the base pairing rule?What would be the complementary nucleotide pairing for these strands?
DNA•DNA is the “instruction manual” (the “recipe book”) which tells the cell what proteins to make•But, DNA is “stuck” in the nucleus
•It is too large to pass through the nuclear membrane
•Which organelle makes proteins?•__________________
•How do the instructions get from the nucleus to the Ribosome???????
RNA – Ribonucleic AcidSmall, Single Stranded COPY of the DNA message
Copy of ONE GENE
RNA is small enough to pass through the nuclear membrane and bring the message to the Ribosome in the cytoplasm3 differences from DNA
This allows the organism to recognize that the RNA is NOT the original!
DNA vs. RNA
RNA is Ribonucleic Acid – DNA is Deoxyribonucleic Acid
An Oxygen molecule is missing… making it “Deoxy”…
RNA is a short, single stranded copyDNA is large, double stranded orginal
RNA contains a different Nucleotide!Uracil (Not Thymine)Remember: ALL UNDER-
ACHIEVERS CAN'T GRADUATE
Rules for RNA Base Pairing
C = G
A = UC
A
T
G
G
U
C
A
DNA
RNA
RNA copies the DNA message by pairing with the DNA nucleotides… An “A” is paired with a “U”. “C” and “G” are always paired together…
ALL UNDERACHIEVERS CAN’T GRADUATE!
What is the function of RNA?
Carries the DNA coded message out of the nucleus
RNA copies the information for one geneOne gene = One protein
Brings message to the RibosomeRibosome reads the code and
makes the correct protein
Types of RNA
There is only ONE Type of DNA
There are THREE Types of RNAMessenger RNA (mRNA)Transfer RNA (tRNA)Ribosomal RNA (rRNA)
You only need to know two!
Nitrogen Base
Sugar
(Ribose)
Phosphate
Group
RNA
RNA Codes for Amino Acids
The nitrogen bases in RNA code for amino acids
Monomers of Protein
A triplet of nitrogen bases codes for one amino acid
The triplet is called a “codon”
(You NEED to know that!)
RNA to Polypeptide
•The Scientific Name for Protein is:Polypeptide- Because peptide bonds hold Amino Acids together
•The Ribosome reads each “codon” (triplet code) and calls for different Amino Acids to be bonded in the chain
•Think “CAN of PEPSI”
Peptide Bond
C N
Overall process of protein synthesis
transcription translation
DNA RNAProtein
What does a chain of amino acids represent?
- a protein!
Threonine
Arginine
Glycine
Glycine
Proline
Asparagine
ProlineAlanine
Polypeptide Chain – A Protein
CodonsOne codon codes for one amino acid.
A sequence of amino acids is a protein... A different sequence makes a different protein!
EX: ACG = amino acid (threonine)
CGC = amino acid (arginine)
GGA = amino acid (glycine)
ACG
GGAGGC
CCA
AAC
CCG
GCCCGC
Threonine
Arginine
GlycineGlycine
Proline
Asparagine
Proline
Alanine
Amino Acid
protein
Let’s Try It…
• DNA “Complementary Pairs”
•Remember:•All Thugs•Carry Guns
Let’s Try It…
• RNA “Complementary Pairs”
•Remember:•All Underachievers•Can’t Graduate