Warmup 2/02
• Who were the authors of the DNA article?
• How many nitrogen bases are found on
DNA?
• What is the name for the structure of DNA
that the authors proposed?
DNA Structure
What is it?
• What is DNA?
• Deoxyribosenucleic Acid
• Located in the nucleus of a cell
• DNA is a nucleic acid
• DNA is made of nucleotides
Nitrogen Bases
• Made of three things
• Phosphate Groups
• Deoxyribose sugar
• Nitrogen Base
Nitrogen Bases
• Nitrogen Bases
• Two bases are called purines (larger)
• Adenine (A)
• Guanine (G)
• Two bases are pyrimidines (smaller)
• Thymine (T) (only found in DNA)
• Cytosine (C)
Nitrogen Bases
• Chargaff’s Rule
• Adenine only pairs with
Thymine
• Guanine only pairs with
Cytosine
• Therefore, for every A there
is a T and for every G there
is a C
Structure
• The DNA has a characteristic
double helix
• Double because there are
two sides
• Helix because it forms a
spiral
• Resembles a twisted ladder
• The structure was discovered by
Watson and Crick
• Contributions were made by Pauling,
Franklin, and Wilkins
Structure
• The nitrogen bases are held together by
Hydrogen Bonds
Hydrogen Bond
• Hydrogen bonds are attractions
between hydrogen atoms on 1
molecule and oxygen atoms on
another. Like a magnet
• Very weak bonds
Sequence
• How the nitrogen bases are arranged are
• Unique to the species
• Unique to the individual
• The more similar the sequence of DNA is,
the more closely related the two species
are
Warmup 9/02
• What are the 3 parts of a nucleotide?
• Where is the DNA found?
• Why does the DNA stay in this structure?
• What are 2 reasons for why organisms look different from
each other even though all of our DNA is made of the same 4
nucleotides?
Warmup 01/04
• Who discovered the structure of DNA?
• DNA is made of what smaller units?
• Describe Chargaff’s Rule.
• What type of bond holds the two sides of
DNA together?
DNA Replication
Making A Copy
• Replication: process of making
an exact copy
Reasons for DNA Replication
•Start Cell Division
•Tissue growth and/or repair
Steps of DNA Replication
• We use the semiconservative model
• You will use the original
piece of DNA as a template
(half the old DNA will be
used in the new DNA strand)
• The right strand will form one
new piece of DNA
• The left strand will form
another new piece of DNA
•Remember that A pairs with T
and C pairs with G
• Each strand is complementary
to the other (it matches)
Helicase
• Step 1: DNA unwinds
• Uses an enzyme called helicase
• You need the weak Hydrogen Bonds so you can
pull the DNA apart easier
Making our DNA longer
• Step 2: Add new nucleotides to the
original DNA strands
• Proteins called DNA polymerases help add
the new nucleotides
Models of DNA Replication
Example of Replication
• Example:
• Original piece of DNA:
• Complementary piece:
A T G C T G T T A
Differences between
DNA and RNA
Making A Protein
RNA Structure
• Ribonucleic Acid
• Made of 3 parts
• Phosphate group
• Ribose sugar
• Nitrogen base
RNA Structure
• Only has one strand
• Nitrogen Bases
• Guanine (G)
• Cytosine (C)
• Adenine (A)
• Uracil (U) (only found in RNA)
Types of RNA
• Types of RNA
• Messenger RNA (mRNA):
complementary copy of DNA
• Ribosomal RNA (rRNA): part of what
makes a ribosome
• Transport RNA (tRNA): transports amino
acids to the ribosome
DNA
RNA
Structure
Double Helix
Single Helix
Sugar
Deoxyribose
Ribose
Bases used
Thymine
Uracil
Location
made
Location
Used
Nucleus
Nucleus
Nucleus
Outside the
Nucleus
Transcribing RNA
• Transcription: Process of making
mRNA
• Steps of Transcription
• RNA Polymerase binds to the DNA
• DNA unwinds only where the
polymerase is bound
• RNA polymerase adds RNA
nucleotides together that form a
complimentary copy of the DNA
• C pairs with G and A pairs with U
• When the mRNA is done being made
it separates from the DNA and leaves
the nucleus
Example
• Example
• Original DNA strand:
G T C A G T A G T T G C
• mRNA strand:
Warmup 9/09
• What is made during transcription?
• What are the steps of transcription?
• What are 2 differences between DNA and
mRNA?
• Where does transcription happen?
Translation
• Translation (mRNA  Protein)
• Process of turning a mRNA
strand into a protein
Translation
• What is a protein?
• Chains of amino acids linked together
• DNA encodes the instructions to make
proteins
• DNA needs to be changed into RNA to
make the protein
• mRNA is read with a ribosome
• The ribosome “reads” the mRNA 3
bases at a time
• These 3 bases are called codons.
• Each codon codes for 1 amino acid
Practice Problems
• Write out the mRNA acodons to the DNA
codons below
• AAT
• CGA
• TAC
• GAT
• tRNA brings the amino acids to the
ribosome
• Ribsome binds the amino acid to
other amino acids with a peptide
bond
• The tRNA forms a complement to
the mRNA codon
• Called an anti-codon
Practice Problems
• Write out the tRNA anti-codons to the
mRNA codons below
• UUA
• GCA
• AUG
• CUA
•You use a codon chart to
determine which amino acid
bonds to the codon
Practice Problems
•Use the codon chart to match
the amino acids to the codons
•UUA
•GCA
•AUG
•CUA
Warmup 9/10
• What is the 3 letter code found on mRNA
called?
• What is the name of the process that creates
proteins?
• What are the monomers that build DNA and
RNA called?
• What are the 3 differences between DNA and
RNA?
Warmup 9/11
• What are the 3 major differences between
DNA and RNA?
• What is the sugar found in RNA?
• How do DNA and RNA work together?
Warmup 9/14
• Which enzyme splits DNA?
• What model is used to describe the
process of DNA replication?
• What does template mean?
Mutations
Mutations
• Change in the DNA of an individual
• Can be caused by
• Radiation
• Chemicals
• Spontaneous
• If it happens in the gametes (sperm or egg
cells), it will be passed on to the children
Types of Mutations
• Point Mutations
• Change in 1 nucleotide base pair in the
DNA sequence
• EXAMPLE
• TTT GGG CCC AAA: Original
• TTT AGG CCC AAA: Mutated
Types of Mutations
• Frameshift Mutations
• Causes the codon reading frame to get
moved up or down one spot
• Insertion: when a new nucleotide gets put
into the sequence
• TTT GGG CCC AAA: Original
TTT GGG ACC CAA A: Mutated
Frameshift Mutations
EXAMPLE
• Deletion: when 1 nucleotide gets removed
from the sequence
• TTT GGG CCC AAA: Original
TTT GGC CCA AA: Mutated
Warmup 9/15
• What is a mutation?
• What is the difference between the 2
types of frameshift mutations?
• How can a mutation be passed on to
offspring?
Warmup 9/16
• Describe the Semi-Conservative Model of
Replication.
• Describe the process of Transcription.
• Translate the following piece of DNA.
T A C G A T T T A