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DNA & RNA
THE GENETIC MATERIAL
Vocabulary you should know…
 DNA: (deoxyribonucleic acid) the material
that contains the information that
determines inherited characteristics
 Nucleotide: in a nucleic-acid chain, a sub-unit
that consists of a sugar, a phosphate, & a
nitrogenous base
More Vocab…
 Nitrogenous base: an organic base that
contains nitrogen, such as a purine or
pyrimidine; a sub-unit of a nucleotide in DNA
or RNA
 Purine: a nitrogenous base that has a doublering structure; one of two general categories
of nitrogenous bases found in DNA & RNA;
either adenine or guanine
More Vocab…
 Pyrimidine:a nitrogenous base that has a single-ring
structure; one of the two general categories of
nitrogenous bases found in DNA& RNA; thymine,
cytosine or uracil
 Base-Pairing Rules: the rules stating that cytosine
pairs w/ guanine & adenine pairs w/ thymine in DNA &
adenine pairs w/ uracil in RNA
More Vocab…
 Complementary Base Pair: the nucleotide bases in one
strand of DNA or RNA that are paired w/ those of
another strand; adenine pairs w/ thymine or uracil, and
guanine pairs with cytosine
 Base Sequence: the order of nitrogenous bases on a
chain of DNA
 Double Helix: shape of a DNA molecule formed when
two twisted DNA strands are coiled into a springlike
structure & held together by hydrogen bonds b/t the
bases
DNA – deoxyribonucleic acid
 The genetic information for an
organism
 DNA contains the instructions that
cells need to make every protein
required for essential life functions
 Found mostly in the nucleus of cells
 Composed of 100’s of 1000’s of
repeating units of nucleotides
DNA
 Photographed through x-ray
crystallography by Rosalind Franklin
in the 1950s (w/ help from Maurice
Wilkins)
 1st model was created by James
Watson & Francis Crick in the ‘50s,
with the use of Franklins x-ray
crystallography picture
Rosalind Franklin
Maurice Wilkins
James Watson & Francis Crick
DNA
 Made of subunits called nucleotides:
 1 phosphate group
 1 deoxyribose – simple sugar **this is
what DNA is named for
 1 of 4 nitrogen bases
 Either purines or pyrimidines
NITROGEN BASES
 Purines: double ringed structure
 Adenine (A)
 Guanine (G)
Nitrogenous Bases
 Pyrimidines: single ringed structure
 Thymine (T)
 Cytosine (C)
STRUCTURE OF DNA
 Shape: double
helix –
repeating units
of nucleotides
**the sequence
of nucleotides
determines
gene function
DOUBLE HELIX
 2 chains of nucleotide monomers
running anti - parallel
 Phosphate groups make up the
backbone of the double helix
 Covalent bonds hold the nucleotides
together by connecting the
deoxyribose of one nucleotide to the
phosphate group of the adjacent
nucleotide
Double Helix Cont’d
 The nitrogen bases of the
nucleotides pair up to link the 2
helixes
 hydrogen bonds b/t the nitrogen
bases hold the strands of the
double helix together
Double Helix Structure
Base-Pairing Rules
 Adenine (A)
& Thymine (T)
are always
together
 Cytosine (C)
& Guanine (G)
must then pair
together
DNA Basics Quiz
1. What is DNA?
2. The first person to photograph DNA was
____________.
3. The first people to make a model of DNA
were ________ & ______.
4. A strand of DNA is made up of repeating
units of __________.
DNA Basics Quiz Cont’d
5. A nucleotide is composed of 3 parts, name
all three.
6. List the 4 different nitrogenous bases.
7. Which part of the nucleotide makes up the
backbone of the strand of DNA?
DNA Basics Quiz Cont’d
8. What type of bonds hold the deoxyribose of
one nucleotide to the phospate of the
adjacent one?
9. What type of bonds hold the
complementary nitrogenous bases
together?
10. Out of Adenine, Guanine, Cytosine &
Thymine, tell me the two complementary
pairs.
DNA Technology
 DNA is manipulated for many
different reasons:
 Crime scene analysis
 Genetic counseling
 Research
 Treatment of disease
DNA Technology
 DNA ID
 Only identical twins have identical DNA
 Only 10% of the human genome varies
between all humans
 The 10% that differs falls on the same
chromosome region so we can isolate
this DNA and use it to make important
discoveries
Identifying DNA
 Step 1: Copying DNA: Polymerase Chain
Reaction
 Method of quickly copying DNA from small
samples
 Step 2: Cutting DNA: Restriction Enzymes
 Restriction enzymes recognize specific short DNA
sequences & cut in or near them
 This isolates the DNA needed for ID
Identifying DNA cont’d
 Step 3: Sorting DNA by Size: Gel
Electrophoresis
 Gel electrophoresis separates DNA according to
size and charge
 Does this by running an electrical current through
gel that the DNA cut by the restriction enzymes
has been placed in, + & - charged pieces move to
opposite ends
 The resulting pattern is called the DNA fingerprint
Identifying DNA
 Step 4: Comparing DNA: DNA Fingerprints
 Compare the DNA sample to other DNA
fingerprints until you find a match, or pattern that
you are looking for
 Accuracy??
 The odds that 2 people will share the same DNA
fingerprint: 1: 100 billion
 # of people on Earth: approx 7 billion
Gel Electrophoresis
Recombinant DNA
 Genetic engineering: the process of altering
the genetic material of cells or organisms to
allow them to make new substances
 DNA recombination/Recombinant DNA:
 Joining together DNA from two different
organisms
DNA Recombination
 Step 1: isolate the DNA and the plasmid of
interest
 Plasmids: small rings of DNA found naturally in
some bacterial cells in addition to the main
bacterial chromosome
 Step 2: restriction enzymes cut the DNA into
fragments
 Step 3: fragments and plasmid DNA are
joined together permanently by DNA ligase
DNA Recombination Cont’d
 Step 4: recombinant DNA plasmids, each
with different fragments of DNA, are inserted
into bacterial cells
 These recombinant DNA plasmids are then copied
each time the bacterial cell copies its own DNA
 Step 5: once a colony of bacterial cells
containing the recombinant DNA plasmids is
created, the recombinant DNA is removed to
be used
Recombinant DNA
Central Dogma of Molecular Genetics
 How we go from DNA to RNA
 1. replication (DNA copies itself)
 2. transcription (DNA acts as a
template for the production of
messenger RNA (mRNA))
 3. translation (mRNA carries coded
information to ribosomes; ribosomes
"read" this information and use it to
make proteins)
The Central Dogma Cont’d
Dogma Cont’d
Replication:
know…
Vocab you should
 DNA replication: process by which DNA is
copied in a cell before a cell divides by
mitosis, meiosis or binary fission
 Helicase: enzymes that separate DNA
strands by breaking the hydrogen bonds that
hold the nitrogenous bases together
Replication:
More vocab…
 Replication Fork: a Y shaped point that
results when the two strands of DNA double
helix separate so that the DNA molecule can
be replicated
 DNA Polymerase: an enzyme that catalyzes
the formation of the DNA molecule
Replication:
More Vocab…
 Semi-conservative Replicaiton: in each new
DNA double helix, one strand is from the
original molecule & one strand is new
 Mutation: a change in the nucleotide-base
sequence of a gene or DNA molecule
Facts about Replication
 Occurs during interphase of both
the cell cycle for mitosis and for
meiosis
 Happens to all of the DNA in the
cell, not just selected parts (every
chromosome)
Replication (of DNA)
1. Strands of DNA separate
a) Helicase enzymes move along the
strand of DNA
b) They break the hydrogen bonds
between the nitrogen bases
c) The two strands separate,
exposing a a Y-shaped region
called the replication fork
Replication: Helicase & the
Replication Fork
Replication Cont’d
2. DNA polymerase enzymes add
complementary nucleotides to the two
separated strands
a) The nucleotides are found free-floating
around inside the nucleus
b) As the nucleotides are added, covalent
bonds form b/t the deoxyribose of one
and the phosphate of the next
Replication:
Cont’d
Adding Nucleotides
2. Adding nucleotides cont’d
c) Hydrogen bonds are formed b/t
the nitrogenous bases from the
original strand and the
nitrogenous bases on the newly
added nucleotides
Replication:
Cont’d
Adding Nucleotides
2. Adding Nucleotides cont’d
d) DNA synthesis (creation) occurs in different
directions on each strand
i. As the replication fork moves along the
original DNA, synthesis of one strand, the
leading strand, follows the movement of
the replication fork
ii. Synthesis of the other strand, the lagging
strand, moves in the opposite direction,
away from the replication fork
Replication:
Cont’d
Adding Nucleotide
2. Adding Nucleotides Cont’d
e) Because the nucleotides are added to
the leading and lagging strands in
opposite directions, it leaves gaps in
the newly synthesized DNA, called
Okazaki Gaps
f) These gaps are later joined together by
the enzyme DNA ligase
Replication:
Strands
Leading & Lagging
Replication Okazaki
Fragments
Replication Cont’d
3. DNA polymerase enzymes finish
replicating the DNA & fall off
The result of replication of a strand of
DNA is two completely identical
strands of DNA, each containing one
old strand & one new stand =
semiconservative replication
Semi-Conservative
Replication
Replication cont’d
 DNA replication flash interactive
DNA Replication Quiz
1. What are the three parts of the Central
Dogma of molecular genetics?
2. What is the first thing that must happen in
order for DNA to replicate itself?
3. What is the name of the enzyme that
separates the two strands of DNA?
Replication Quiz Cont’d
4. Helicase breaks the ________ bonds that
hold the nitrogenous bases together.
5. The Y-shaped region that appears as the two
strands separate is called the ________
_______.
6. After the strands separate, what is the
second thing that happens as DNA replicates
itself?
Replication Quiz Cont’d
7. What is the name of the enzyme that adds
the free-floating nucleotides to the two
exposed strands of DNA?
8. The gaps created as the new DNA strands
are being synthesized are called _________
__________.
Replication Quiz Cont’d
9. What happens to the DNA polymerase after
is finished being replicated?
10. Replication results in _____ (#) strands of
DNA, each having one ____ strand and one
_______ strand.
RNA:
Vocabulary You Should Know
 Ribonucleic Acid (RNA): a natural polymer that is present in all
living cells & that plays a role in protein synthesis
 Transcription: the process of forming a nucleic acid by using
another molecule as a template; particularly the process of
synthesizing RNA by using one strand of a DNA molecule as a
template
 Translation: the portion of protein synthesis that takes place at
ribosomes & that uses the codons in mRNA molecules to specify
the sequence of amino acids in ploypeptide chains
RNA:
move vocab…
 Protein Synthesis: the formation of proteins by using
infomration contained in DNA & carried by mRNA
 Ribose: a five-carbon sugar present in RNA
 Messenger RNA (mRNA): a single-stranded RNA
molecule that encodes the information to make a
protein
RNA:
more vocab…
 Ribosomal RNA (rRNA): an organelle that contains
most of the RNA in the cell & that is responsible for
ribosome function
 Transfer RNA (tRNA): an RNA molecule that transfers
amino acids to the growing end of a polypeptide chain
during translation
 RNA Polymerase: an enzyme that starts (catalyzes)
the formation of RNA by using a strand of DNA
molecule as a template
RNA:
More vocab…
 Promoter: a nucleotide sequence on a DNA molecule to which
an RNA polymerase molecule binds, which initiates the
transcription of a specific gene
 Termination Signal: a specific sequence of nucleotides that
marks the end of a gene
 Genetic Code: the rule that describes how a sequence of
nucleotides, read in groups of three consecutive nucleotides
(triplets) that correspond to specific amino acids, specifies the
amino acid sequence of a protein
RNA:
More Vocab…
 Codon: in DNA, a three-nucleotide sequence that
encodes an amino acid or signifies a start signal or a
stop signal
 Anticodon: a region of tRNA that consists of three
bases complementary to the codon of mRNA
 Genome: the complete genetic material contained in
an individual
RNA – Ribonucleic Acid
RNA:
Structure & Comparison to DNA
 RNA
1. Single stranded
2. Sugar = ribose
3. Nitrogenous bases:
1. Adenine
2. Cytosine
3. Guanine
4. Uracil
4. Usually much
shorter
 DNA
1. Double stranded
2. Sugar = deoxyribose
3. Bases:
1. Adenine
2. Cytosine
3. Guanine
4. Thymine
4. Usually much
longer: 100s or
1000s of genes
RNA v. DNA
RNA:
Types of
1. mRNA: messenger RNA
 Single stranded
 carries instruction from a gene to
make a protein
 Eukaryotic cells: carries messages
from DNA in the nucleus to a
ribosome in the cell’s cytoplasm
mRNA
RNA:
Types of …
2. tRNA: transfer RNA
 transports amino acids to the
ribosomes (rRNA) to be
assembled into proteins
 Made of many nucleotides
linked together
tRNA
RNA:
Types of …
3. rRNA: ribosomal RNA
 This type of RNA makes up a part of
ribosomes
 Ribosomes are organelles in each cell
where protein synthesis occures
 clamp onto the mRNA & use its info to
assemble amino acids in the correct
order to make proteins
rRNA
COMPOSITION OF RNA
 Made of nucleotides:
 1 phosphate group
 1 ribose – type of sugar
 1 of 4 nitrogen bases
RNA’s NITROGEN BASES
 Purines:
 Adenine (A)
 Guanine (G)
 Pyrimidines:
 Cytosine (C)
 Uracil (U) ***instead of
Thymine
RNA Base-Pairing Rules
 Adenine pairs w/ Uracil (because
there is no thymine)
 Cytosine pairs w/ Guanine
RNA BasePairing
RNA Quiz
1. Protein synthesis results in the creation of
2.
3.
4.
5.
6.
7.
________.
RNA has _______ strands.
RNA has the sugar _________.
Name the 4 bases for RNA.
RNA is usually ______ than DNA.
Name the 3 types of RNA.
What does mRNA do?
RNA Quiz Cont’d
8. What does tRNA do?
9. rRNA is found on what cell part?
10. What are the base-pairing rules for RNA?
Transcription
 The rewriting of genetic instructions
from DNA into RNA
 “transcribes” DNA into genes
 Takes place in the nucleus of
eukaryotic cells
 Takes place in the cytoplasm of
prokaryotic cells
Transcription Steps
1. Unwinding & separating the DNA
strands
 The enzyme RNA polymerase
binds to a promoter (a specific
codon that starts transcription) on
the DNA molecule
 DNA unwinds & separates
Transcription Steps:
Separating DNA
Unwinding &
Transcription Steps
2. Adding RNA nucleotides to create a strand of
RNA
 RNA polymerase adds free-floating RNA
nucleotides to one of the exposed DNA
strands
 The nucleotides that are added are
complementary to one of the DNA strands
 Only a specific section of the DNA strand is
used to create the strand of RNA
Adding RNA Nucleotides
Transcription Steps
3. Release of the RNA molecule
 RNA polymerase reaches a termination
signal that tells it to stop
 RNA polymerase releases both the DNA &
the newly formed RNA molecule
 RNA created is mRNA
 The RNA molecule is free to perform its “job”
 RNA polymerase is available to transcribe
more genes
Releasing both DNA & RNA
Transcription Quiz
1. Transcription rewrites what?
2. Where does transcription take place in
eukaryotic cells?
3. What is the 1st step in transcription?
4. What is the enzyme that unwinds &
separates DNA?
Transcription Quiz Cont’d
5. What is the second step of transcription?
6. What are added to the exposed strand of
DNA?
7. What tells RNA polymerase when to stop
adding nucleotides?
8. The newly formed RNA is __RNA.
Transcription Quiz Cont’d
9. When RNA polymerase reaches the terminal
signal it releases both _______ & _______.
10. What does RNA polymerase do after it
releases the DNA & newly formed RNA
molecule?
Protein Synthesis
 Gene: segment of DNA , located on a
chromosome that codes for a
hereditary characteristic (like hair
color)
 Genes direct the synthesis or making
of proteins for that particular trait
 Genes use RNA to help make the
appropriate proteins
Protein Synthesis
 Genetic information flows in the following
order:
 Transcription
 Translation / Protein synthesis
 DNA → RNA → protein
 Proteins are important b/c they create &
do everything that our body is & does
The Genetic Code
 The code needed to convert the language of




mRNA into proteins
Proteins are made of amino acids
Amino acids are made based on the
nucleotide sequence in mRNA
3 adjacent nucleotides in mRNA specify a
particular amino acid
The 3 nucleotide sequence that encodes an
amino acid, a start signal or a stop signal = a
codon
Codons
 Codons can only code for one amino acid
 i.e.: UUA = Leucine and only leucine
 Each amino acid can be coded for by more
than one codon
 the amino acid leucine can be coded for by all of
the following codons
 i.e.: UUA = Leucine, UUG = Leucine

CUU = Leucine, CUC = Leucine

CUA = Leucine, CUG = Leucine
Codons Cont’d
 Start codons: sequence of nucleotides in
mRNA that signals where translation should
begin
 Codes for the amino acid methionine
 Stop codons: sequence of nucleotides in
mRNA that signals where translation should
stop
 Does not code for any amino acid
Codons in mRNA
Proteins
 Made of polypeptides
 Polypeptides are chains of amino acids linked by
peptide bonds
 20 different amino acids
 Polypeptide chains are 100s of 1000s of amino acids
long
 The sequence of amino acids determine how the
protein will fold & twist into a 3d shape, the shape
gives the protein its function
Proteins
Translation
 Is the synthesis or making of a protein
 The instructions for making a protein are
transcripted from DNA into mRNA
 All three types of RNA are involved in
translation
Translation Steps
1. Joining RNAs




rRNAs & tRNAs attach to a mRNA
Enzymes attach an amino acid to one end of
each tRNA
The other end of the tRNA contains the
anticodon for mRNA
A tRNA carrying the amino acid methionine
must be present to start the reading of mRNA &
attaches to a start codon on mRNA
T-RNA
Translation
Translation Steps Cont’d
2.
Creation of a polypeptide chain





tRNAs carrying correct amino acids, pair their anticodons w/
the codons on the mRNA strand
Methionine detaches from the 1st tRNA after the 2nd
anticodon is added
A peptide bond forms b/t methionine & the 2nd amino acid
to start a polypeptide chain
The 1st tRNA exits the ribosome
Ribosome moves one codon down on the mRNA strand
Translation
Translation Step Cont’d
3. Polypeptide Chains Grow
 mRNA continues to move through the ribosome
 New tRNAs w/ correct anticodons move in &
peptide bonds are created b/t the amino acids of
each tRNA
 The polypeptide chain moves from one tRNA to
the next tRNA & attaches to its amino acid
Translation
Translation Steps
4. Stop Codon


Polypeptide grows one amino acid at a time until
it reaches a stop codon
Polypeptide falls off
Translation
Translation Steps Cont’d
5. End of Translation
 All the parts that are needed for translation
come apart
 The last tRNA exits the ribosome
 The ribosome moves away from the mRNA
 All the parts are free to be used over & over
again
Translation
Translation Quiz
1. Proteins are made of ____ ____, which are
made of 3 RNA ______.
2. Polypeptides are chains of amino acids
linked by _____ ____.
3. Translation is the synthesis of ________.
4. List the types of RNA involved in protein
synthesis.
Translation Quiz Cont’d
5. The first tRNA to be used during translation
must carry the amino acid ________.
6. A polypeptide chain is started when
methionine is bonded to the __________.
7. For the polypeptide chain to grow the mRNA
must ____________.
Translation Quiz Cont’d
8. The polypeptide chain stops growing when it
reaches the ______ ________.
9. When the polypeptide chain reaches the
stop codon what happens to the chain?
10. Once the polypeptide chain falls off, what
happens to all the parts that assembled to
translate RNA?