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DNA
Deoxyribonucleic Acid
Nature vs. Nurture?
DNA
We know traits
are inherited
but how are
they inherited?
Chargaff’s Rule
Chargaff’s Rule
X-ray Evidence
• 1952 Rosalind
Franklin took an
x-ray diffraction
to take picture of
DNA shape
• Picture gave
clues to structure
of DNA
Watson & Crick
• Watson &
Crick made a
model of DNA
structure
• Won Nobel
Prize
Watson and
Crick’s model
of DNA was a
double helix
The Components & Structure of
DNA
Nucleotide
1. 5-carbon sugar
deoxyribose
2. phosphate
group
3. nitrogenous
base
i. Adenine
ii. Thymine
iii. Guanine
iv. Cytosine
Nucleotides are monomers!
• Nucleotides are
linked in a strand
• The sides of the
“ladder” are
phosphates and the
sugar deoxyribose
- Sugar & phosphate form backbone
- The bases form the “steps” of ladder, held
together by Hydrogen bonds
• C-G = 3 hydrogen bonds
• A-T = 2 hydrogen bonds
How is DNA Packaged?
• DNA is wrapped around proteins
called histones forming beads
• These beads pack together, forming
nucleosomes.
• These coil to make chromatin
• When the chromatin (stringy DNA) coils it make a
chromosome
DNA Replication
• Think about DNA’s
structure
• Perfect for use of
replication!
• Each original side
is a Template
Parent Strand
Or Template
Daughter
strand
Before a cell divides, it duplicates its
DNA in a process called replication.
• This makes sure each cell will have a
complete set of DNA
How is it done?!
1. DNA is unwound
2. DNA helicase enzyme unzips the weak
hydrogen bonds between base pairs
3. DNA polymerase enzyme matches up
nucleotides to complement the other
side
4. Strands checked for error
“Semi-conservative”- why?
Replicate your own DNA
• 1. Take piece of paper and fold is
vertically
• NOW REPLICATE
Label
1.
2.
3.
4.
5.
6.
Template/ Parent Strand
Hydrogen Bonds
Complementary Base Pairing
DNA Helicase
DNA Polymerase
Daughter Strands
Central Dogma
• DNA  RNA Protein
• DNA gives the instructions for RNA which
gives the instructions to make proteins
Central Dogma
What is a gene?
• Part of the DNA
(letters/bases) that
code for a
particular protein
Genotype
vs. Phenotype
• Genotype, genetic
makeup, is the
sequence of bases
in the DNA
• Phenotype, traits,
due to proteins
Proteins we learned!
Structural
• Keratin ( hair, skin and nails )
• Muscles
Reactions
• Enzymes (lactase)
Signal
• Insulin, human growth hormone
Hemoglobin- carriers oxygen in
your red blood cells
RNA vs DNA
•
•
•
•
RNA
Ribonucleic Acid
Ribose Sugar
A,C,G,U
– U = Uracil
• Single Stranded
Transcription
1. RNA copies the
message from DNA Called messenger
RNA ( mRNA)
2. Complementary
base pair ( NO T!! In
RNA)
3. Only copies a gene
of the DNA
4. mRNA Leaves the
Nucleus
Transcription
• Enzyme that build RNA
strand
• RNA polymerase
RNA Splicing
Introns stay in the nucleus
Exons join (splice) together and exit – final mRNA
Translation
mRNA to Protein
1. mRNA goes to the Ribosome
– Each 3 letters of the mRNA is called a codon
2. Each mRNA codon bonds to a tRNA
(transfer RNA) anticodon
– Complementary Base paring rules
3. tRNA carries the amino acid which builds
the polypeptide (protein)
4. Begins with mRNA start codon AUG and
ends with mRNA STOP Codon
Introduction Worksheet
• http://learn.genetics.utah.edu/content/begi
n/dna/transcribe/
• Transcribe and Translate a Gene
SHOW REAL TIME
• Great Simple Video!!
Mutations
http://www.dnalc.org/resources/3d/17-sicklecell.html
1 base change in 438-base sequence.
Change in DNA, change in RNA, change in Amino Acid
Hemoglobin protein does not work properly to carry oxygen.
Tay Sachs
Cracking the Code:17:00-20:00
Inherited genetic
mutation
• Mutation in a gene
that codes for an
enzyme protein that
breaks down fatty
acids in the brain
Mutation
• Change in the nucleotide Sequence (
letters/bases) of a gene
1. Base Substitution (can be bad or silent)
2. Base Addition/ Deletion- worse
- Frameshift mutation= alter group of 3
Affects the function of the PROTEIN
ADDITION
• THE CAT ATE THE RAT
• THE ACA TAT ETH ERA T
Mutagens cause Mutations
• Xray, UV light, smoking chemicals,
pesticides
• Sometimes GOOD? How so?
Example of Inherited DNA
Mutations: Diseases
Mutations