1#___ Name:_____KEY___________ Date:______ Period: _____
DNA: The Molecule of Heredity &
Understanding How Your Body Works!...“From Gene to Protein”
 Note-Taking Sheet- (Keep in your Notebook to study!) 
Today we will learn:
 The structure and purpose of DNA & RNA
 We will investigate 3 major processes that involve DNA & RNA
A. Semiconservative replication= the process of copying/doubling the amount of
DNA prior to cell division so the daughter cells both get a full set.
The next two processes occur back to back, and this is how your genes make
your body work. Each gene codes for specific protein(s) each individual cell
needs to function properly and keep you alive. Many of these proteins are
enzymes that speed up reactions, some are structural proteins, and they
make other types of proteins that are important for your cells to function.
This process of going from Gene to Protein occurs in two stages:
B. Transcription= process of copying the gene on the DNA strand into a working
copy of mRNA.
C. Translation=the process of building a protein using the “working mRNA copy” of
the original gene.
Ok, now on with the show!
So, what exactly is this DNA STUFF Anyway???
DNA’s Official Name: Deoxyribonucleic acid
 DNA is a type of nucleic acid
 Chromosomes (and genes) are made of DNA
Putting it all together: Chromosomes are long strands of DNA-> each contain many
genes-> which is a section of DNA that codes for a trait. Each section of DNA is
made of individual nucleotide subunits that are read in sets of three.)
 DNA is made up of repeating nucleotide subunits. (3 million base pairs!)
 Each nucleotide represents half of the helix and consists of a
1. phosphate group, 2. Sugar, and 3. nitrogenous base.
Deoxyribose
Sugar
Phosphate
Group
Nitrogenous
Base
Adenine
Of bases: Guanine
Cytosine
Thymine
4 types

Has 2 strands, so bases can pair up
o A binds T only (Think “at”)
o C binds G only
Strand 1
Strand 2
P
S
Remember
P
A
T
P
S
(A)
(G)
(C)
(T)
S
DNA is like an Oreo
P
C
G
S
Phosphates + sugar = cookies
bases = cream filling
Bases on the ladder’s steps (Bases fit like puzzle pieces)
Phosphates + sugars
on the sides
Shape is a Double Helix
o Double helix: 2 spirals wound around each other
o Rosalind Franklin took an X-ray photo of DNA.
o James Watson and Francis Crick interpreted the photo and
discovered the double helix structure. They won the Nobel Prize.
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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Triplet= Group of 3 DNA bases
that represents the
matching set for the
codon
CODON= 3 bases on mRNA;
(which is the
complement “copy” of
the DNA triplet)

Genes: stretch of DNA that codes for a trait. (20,000 protein coding genes)
o The code is the order of the bases (letters)
o Genes are hundreds or thousands of bases long
Eye color gene
Dimples gene
Hair color gene
Chargaff’s Rule
A scientist named Chargraff measured the amount of each base in DNA samples
and determined how they fit together based on the % of each.
 HIS FINDINGS= In DNA, the amount of Adenine = the amount of Thymine
the amount of Cytosine = the amount of Guanine
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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So, they figured out that the DNA HELIX is Complementary!
 Complementary: bases on one strand of the helix match up with the bases on the
other strand (A-T and G-C)
 Example: Strand 1- A T G G G C C T A
Strand 2- T A C CCG G A T
During S-phase of Interphase, the DNA is replicated (copied) so there are 2
individual sets of DNA for each new daughter cell. This Synthesis phase is when
DNA Replication occurs. But it took a while for scientists to figure out how it
happened.
DNA Replication
 Replication is the process by which DNA copies itself
 Happens during S-phase of Interphase when chromosomes copy themselves
before mitosis and meiosis.

Semi-conservative replication: Each new piece of DNA is made up of 1 original
strand and 1 new strand
Original DNA helix
Helicase (enzyme) unzips
DNA polymerase enzyme that copies &
proof reads) Each original strand into a
new strand; which limits errors!!
DNA never ever leaves the nucleus
 DNA is the master copy (or master blueprint) of the directions a cell
needs to live so it needs to be protected
DNA in
the
nucleus
is Sheet: From Gene to Protein
Mrs. Lambert’s
Note-taking
safe!
But DNA in
the cytoplasm
can be
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destroyed
mRNA is a working copy of DNA that goes out into the cytoplasm to tell the cell
what to do in order to stay alive & perform all of its duties.
 RNA: nucleic acid
 You can always make more RNA, so it’s ok if it gets destroyed
 RNA is divided into 3 types, each with a different job.
1. mRNA (messenger RNA) = working copy of the gene
2. tRNA (transfer RNA) = is a mini shuttle (bus) to take amino acids to mRNA
3. rRNA (ribosomal RNA) = makes up ribosomes which is the “protein factory”
DNA
2
How many
strands?
Nucleotide
subunit
Bases
Phosphate
Group
deoxyribose
______________
Sugar
RNA
1
Nitrogen
Base
Deoxyribose sugar
Thymine (T)
T–A
Adenine (A)
Guanine (G)
G–C
Cytosine (C)
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
Phosphate
Group
Ribose
Sugar
Nitrogen
Base
Ribose sugar
Uracil (U)
U–A
Adenine (A)
Guanine (G)
G–C
Cytosine (C)
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UNDERSTANDING TRANSCRIPTION- From DNA-> mRNA
Transcription- the process of making a mRNA “working copy” of the
“master gene” made of DNA
 The type of RNA made is called mRNA (messenger RNA) because it
sends a message from DNA to the cytoplasm
DNA safe in the
nucleus
Uses mRNA
(working copy of the gene)
To send a
message to the
cytoplasm
Transcription- Happens Like This:
1. An enzyme called Helicase unzips the DNA
2. An enzyme called RNA polymerase copies the
exposed DNA strand and matches up bases to
make a “working copy” of it called mRNA.
3. mRNA separates from the DNA
4. mRNA moves out of the nucleus through
nuclear pores and into the cytoplasm
What is different about the RNA bases?
DNA: GAG AAC TAG TAC
RNA: CUC UUG AUC AUG
That is right! RNA doesn’t have T; it has U
For figuring out RNA:
A binds U
C binds G
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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OVERVIEW OF TRANSCRIPTION!
DNA
mRNA
mRNA
A
Cytoplasm
of cell
Nucleus
Transcription
happens in the
nucleus. An
mRNA copy of
a gene is made.
Then the mRNA
that has been
made moves out
of the nucleus
into the
cytoplasm
Once in the
cytoplasm, the
mRNA is used to
make a protein.
Which is called
Translation!
How does mRNA tell the cell what to do?
 mRNA is a message that codes for a protein
 Proteins are made in the cytoplasm and then work to keep the cell alive
Translation (protein synthesis): Process of making a protein
 Proteins are made up of amino acids (small building blocks)
 There are 20 different types of amino acids
Protein
Amino Acids
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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Nucleus
Process of Translation
1. mRNA moves OUT
of nucleus and into
cytoplasm
Cytoplasm
2. mRNA attaches
to a RIBOSOME
3. Transfer RNA (tRNA) shuttles the
matching Amino Acid to the
mRNA/Ribosome complex to build
up the protein
tRNA
Ribosome
Amino
acid
Anticodon (3 bases on tRNA):
Matches up to the
Codons on mRNA
4. PROTEIN! (chain of amino acids)
detaches from ribosome and goes
off to work in the cell
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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Genetic Code- “An individual’s sequence of genes that code for proteins and noncoding regions. This is also called the GENOME!
DNA- mRNA Protein. The chain of amino acids is the protein.
mRNA
codons
(3 bases)
Pairs with
anticodons on
tRNA thus
delivering
the next
Amino acid.
Start codon- indicates the beginning
of the gene and the
Stop codon – codes for the end of the
mRNA (no amino acid added)
1. Read your mRNA codon 
ACU
2. Find 1st base on the left, 2nd base on the top, 3rd base on the right.
Find where they all cross in the chart.
3. Read your amino acid.

Threonine
There are different codons code for different amino acids!!!
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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Central dogma of molecular biology
Transcription
DNA
Directions to
make proteins are
safely stored in
the nucleus
Translation
mRNA
Carries the
directions to
the cytoplasm
Protein
Work to keep
the cell alive
**Now lets talk about when things don’t work as planned…
Mutations
 a CHANGE in the DNA sequence
 It’s a mistake that’s made during replication or transcription
 can be harmful: cancer or deformities
helpful: organism is better able to survive
neutral: organism is unaffected
 if a mutation occurs in a sperm or egg cell, that mutation is passed on to
offspring (germline mutation)
 if a mutation occurs in a somatic cell, that mutation affects only the
organism and is NOT passed onto offspring
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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Types of mutations
1. Point mutations: BASES are mismatched
 Harmful when: a mistake in DNA is carried into mRNA and results
in the wrong amino acid
Correct DNA
Correct mRNA
GAG
CTC
Point mutation in DNA
GCG
CTC
Correct amino acid
CUC
Leucine
Mutated mRNA
Wrong amino acid
CGC
Arginine
A should pair with T, but instead C is mismatched to T
Not harmful when: a mistake in DNA is carried into mRNA but still
results in the correct amino acid
2. Frameshift mutations: bases are inserted or deleted
 Are usually harmful because a mistake in DNA is carried into
mRNA and results in many wrong amino acids

Correct DNA:
ATA
TAT
CCG
GGC
TGA
ACT
Correct mRNA:
UAU
GGC
ACU
Correct amino acids: Tyrosine
Glycine
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
Threonine
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Extra inserted base shifts how we read the codons (3
bases), which changes the amino acids
Frameshift mutation
in DNA:
ATG
TAC
ACC
TGG
GTG
CAC
A
T
Mutated mRNA:
UAC
UGG
CAC
U
Wrong amino acids: Tyrosine Tryptophan Histidine
3.



Chromosomal mutations
chromosomes gained or are lost during mitosis or meiosis
broken chromosomes may rejoin incorrectly
almost always deadly when it occurs in a zygote
Causes of mutations
 Mutagens are anything that can cause a change in DNA;
 Examples: X rays, UV light (sunlight), nuclear radiation, asbestos,
cigarette smoke
 Usually, harmful mutations are most commonly discussed if something is
mutagenic, but it doesn’t have to be harmful.
 Carcinogens= include any agent that causes cancer. (90% of these agents
are also mutagens because it caused a changed in the DNA that lead to
developing cancer.)
Mrs. Lambert’s Note-taking Sheet: From Gene to Protein
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