Ch. 5: DNA and
Modern Genetics!!
“The Molecule of Life”
Do Now!! 
 What is DNA?
 Why is it important?
 List three places in the body where you can
find DNA.
Objectives
 To explain the structure of DNA
 To identify the different types of bases how
they pair up
 To list the scientists involved in discovering DNA
So what is DNA?
 A molecule that stores information
 What do the letters stand for?
 DEOXYRIBONUCLEIC ACID
 Where is it found?
 In the nucleus (or nuclear region in prokaryotes)
 What is it used for?
 Blueprints of your genes/traits
 To make proteins!
What is DNA Made of?
 Repeating units of nucleotides
 Nucleotides are made of 3
components:
 5 carbon sugar (Deoxyribose)
 Phosphate Group
 Nitrogenous base
Nitrogenous Bases
 Purines
Have 2 rings (double ring
structure)
a. Adenine (A)
b. Guanine (G)
 Pyrimidines
Have 1 ring (single ring structure)
a. Thymine (T)
b. Cytosine (C)
c. Uracil (U) instead of Thymine
in RNA
Nitrogenous Bases
Chargaff’s Rule
 Erwin Chargaff
 Discovered that A pairs with T
and C pairs with G.
 Chargaff’s rule:
A=T, C=G
 Amounts vary between
species
What is the complimentary sequence??
ATGCTAATTCGCATCG
Do Now! 
 What makes up a nucleotide?
 What is the difference between a purine and a
pyrimidine? Identify the purines and pyrimidines we
talked about!
 Please write the complementary sequence:
TGACCAGTTTAGCTAGGGC
Objectives
 To identify the scientists who contributed to the discovery of
DNA
 To define the structure of DNA
 To complete a DNA structure worksheet
Rosalind Franklin
Used X-ray diffraction to
determine shape of DNA
X-ray diffraction:
X-rays aimed at molecule,
bounce off electrons
Determines the
molecule’s shape
Rosalind Franklin
 Took now famous photo 51
 Data indicated that DNA was a
double helix shape
 Helped Watson and Crick solve
the structure of DNA
Watson and Crick
 Built a model of the double
helix DNA molecule:
two outside strands
consist of alternating
sugar and phosphate
molecules
thymine and adenine
bases pair to each other
by two hydrogen bonds
cytosine and guanine
bases pair to each other
by three hydrogen bonds
*Go back to your DNA sequence!
DNA Structure
DNA looks like a twisted
ladder!
Rails: alternating
deoxyribose sugars and
phosphates
Rungs (steps): base
pairs (C-G, A-T) bonded
by hydrogen bonds
Do Now! 
Label the parts of the DNA!
A
B
C
D
Objectives
 To review DNA structure
 To define DNA replication
 To identify the steps of DNA replication
DNA Replication
 Allows cells to get an exact
copy of DNA.
 Replication:
Parent strands separate,
serve as templates
Daughter DNA
produced (have one
DNA strand from parent
and one new strand)
Steps to Replication
 1- The two DNA strands unwind and
separate:
 Helicase- enzyme that separates
the DNA molecule
Steps to Replication
o 2- Nucleotides match up base by base with the nucleotides on each
TEMPLATE DNA strand:
 All of the C’s pair with the G’s and all of the A’s pair with the T’s.
 DNA Polymerase: enzyme that creates new DNA by assembling
nucleotides
Steps to Replication
 3- Each new daughter DNA
molecule has one strand of new
DNA and one from the original
parent strand.
Replication Animation!
 http://highered.mheducation.com/sites/0072943696/student_v
iew0/chapter3/animation__dna_replication__quiz_1_.html
Do Now!! 
 Please complete the worksheet in front of you!
Objectives
 To define RNA
 To identify the different types of RNA
 To define transcription and translation
So why do we NEED DNA??
We need to make RNA to make
proteins!!
 What is RNA?
Ribonucleic Acid
 How is it different from
DNA?
Single stranded
Indefinite shape
Uses “uracil”
Contains Ribose
Types of RNA
1. Messenger RNA (mRNA):
Linear
Located in both the
nucleus and the
cytoplasm
Brings genetic code
from DNA to the
ribosome to make
protein (in cytoplasm)
Contains codons (every
3 letters, ex. AUG is 1
codon)
Types of RNA
 2. Ribosomal (rRNA):
Located within the ribosome
Helps make the structure of the ribosome
Types of RNA
 3. Transfer (tRNA)
Located in the cytoplasm
Clover-like loop structure
Brings amino acids (attached to
top of tRNA) to ribosome to help
build proteins
Contains anticodon (3 letter
sequence at bottom of tRNA,
complements codon)
The Central Dogma!
 DNA
RNA
Protein
 Transcription:
 Occurs in nucleus
 Create (transcribe) mRNA from DNA
template
 Translation:
 Occurs in cytoplasm
 Takes mRNA and makes proteins with the
help of tRNA and ribosomes.
Do Now!! 
o Please take out your worksheet from last class
and finish!
Objectives
 To identify the steps of transcription.
 To understand the process of transcription and
how mRNA is made.
Transcription
o Gene: a distinct sequence of
nucleotides
o Determines your traits
o Only individual genes are
transcribed, not a whole DNA
molecule
o Occurs in the nucleus
o Produces mRNA
Transcription
 Step 1: DNA molecule unwinds and separates just like in
replication:
RNA polymerase: enzyme that unwinds the DNA and
assembles new nucleotides (makes RNA strand).
Transcription
 Step 2: RNA nucleotides match up with their
complimentary bases on the DNA template strand:
 RNA polymerase assembles these nucleotides
 Creates a single stranded mRNA molecule
 Practice: Write the complimentary mRNA strand from this
DNA
 ATCGATGGCAAGCTA
Transcription
 Step 3: mRNA detaches once entire
gene is done and DNA rewinds:
 mRNA strand leaves nucleus
through pores
 Goes to cytoplasm to help
ribosomes make proteins
 *Delivers directions from DNA for
how to make proteins
*Many copies of RNA can be made
from the same gene in a short period
of time.
Transcription Video
 http://www.dnalc.org/resources/3d/12-transcription-basic.html
Do Now!! 
 With a partner, please complete the worksheet in front
of you!
Do Now!! 
 What is the “Central Dogma”?
 What is transcription?
 Please transcribe the DNA sequence below:
T A C C G A A T C G T A C G G A C T
Objectives
 To define translation
 To identify the steps of translation
 To practice building amino acid sequences to
form proteins
Translation
 What happens in the steps before translation?
 What happens in translation?
 Where does this happen?
Translation
 Step 1: Translation begins when a ribosome attaches to the beginning
of an mRNA molecule.
 *Translation MUST START AT THE LETTERS “AUG”:
 This is the START codon
 * Every 3 letters on the mRNA is called a “Codon” that codes for a
specific amino acid.
CODON BINGO!!
Do Now!! 
 What is translation?
 Where does translation take place?
 Write the amino acid sequence this mRNA strand
would form:
A U G C G G C U A A U U
Objectives
 To identify the steps of translation
 To practice the process of protein synthesis
Translation
 Step 2: A tRNA molecule carrying an amino acid matches
up to a complementary codon in the mRNA on the
ribosome:
 *tRNA molecules contain “Anticodons” which are 3 bases on
bottom of tRNA
 Anticodons compliment codons on mRNA
Translation
 Step 3: The ribosome attaches one amino acid to another
as it moves along the mRNA molecule.
Amino acids are attached by PEPTIDE BONDS.
Translation
 Step 4: The tRNA molecules are released after the amino
acids they carry are attached to the growing chain of
amino acids.
 Return to cytoplasm to pick up another amino acid
Translation
 Step 5: The ribosome completes the translation when it
reaches a stop codon:
 The newly made protein is then released.
Do Now!! 
 Please complete the worksheet in front of you!
Objectives
 To define genetic mutation
 To identify the different types of genetic mutations
What is a mutation?
Mutation: a permanent change
in a cell’s DNA
Errors can occur when DNA is
copied
UV light, X-rays, chemicals, etc.
can cause mutations in DNA
Types of mutations
Substitution – Exchanges one base for another.
Normal:
ACAGAG
Mutated: ACAGGG
 Insertion – Extra base pairs are inserted.
Normal:
AATGAG
Mutated: AATGTGGAG
Types of mutations (cont.)
Deletion- Section of DNA is lost or deleted.
Normal: CTGGAG
Mutated: CT___AG
Frameshift- Message is no longer read correctly.
Normal: THE FAT CAT ATE THE BIG RAT
Mutated: HEF ATC ATA TET HEB IGR AT
What happens when there is a mutation?
Cells have different ways to repair
mistakes:
Proofreading enzymes can correct
mismatched base pairs
EX: DNA polymerase, exonuclease
Do Now!! 
 What are the three kinds of mutations?
 What is a frameshift?
 Are all mutations bad?
Objectives
 To discuss the effects of genetic mutations on protein
synthesis
 To complete a review protein synthesis worksheet
 To simulate genetic mutations in a lab activity
Mutations can have different effects
1. The mutation has no effect:
o
Amino acids have more than 1 code
2. The effect of a mutation is minor:
o
Could affect skin/eye/hair pigmentation
3. The effect of a mutation is great:
o
Genetic disorder/disease
Genetic disorders
Sometimes passed from parents to offspring:
Sickle Cell Anemia
Cystic Fibrosis (CF)
Hemophilia
Tay- Sachs Disease
Huntington’s Disease (HD)
Cancer
Sickle cell anemia
Mutation occurs on gene that
codes for hemoglobin:
Hemoglobin – a protein that
carries oxygen in red blood cells
Substitution mutation causes 1
amino acid to be replaced with
another