Download DNA & Protein Synthesis

1
DNA
• DNA is often called
the blueprint of life.
• In simple terms,
DNA contains the
instructions for
making proteins
within the cell.
2
Watson & Crick’s Model
3
History
• Rosalind Franklin & Maurice Wilkins had
taken the 1st pictures of DNA using X-ray
crystallization
This proved that DNA had a helical shape.
History
• The Nobel Prize in Medicine 1962
Francis Harry Compton Crick
James Dewey Watson
Rosalind Franklin
(Died of cancer 1958)
Maurice Hugh Frederick Wilkins
Watson
Crick
Wilkins has become a
historical footnote and
Watson & Crick are
remembered as the
Fathers of DNA
Why do we study DNA?
We study DNA for
many reasons,
e.g.,
• its central
importance to all
life on Earth,
• medical benefits
such as cures for
diseases,
• better food crops.
9
Chromosomes and DNA
• Our genes are on
our
chromosomes.
• Chromosomes
are made up of a
chemical called
DNA.
10
The Shape of the Molecule
• DNA is a very long
polymer.
• The basic shape is
like a twisted ladder
or zipper.
• This is called a
double helix.
11
The Double Helix Molecule
• The DNA
double helix
has two
strands
twisted
together.
12
One Strand of DNA
• The backbone or
sides of the ladder
of the molecule are
alternating
phosphates and
deoxyribose sugar
• The teeth or rungs
of the ladder are
nitrogenous bases.
phosphate
deoxyribose
bases
13
Nucleotides
One deoxyribose together with
its phosphate and nitrogen base
make a nucleotide.
O
O -P O
Nitrogenous
base
O
O
Phosphate
C
C
O
C
Deoxyribose
14
Nucleotides
O
O -P O
O
O
O -P O
One deoxyribose together with
its phosphate and base make
a nucleotide.
O
O
O -P O
Nitrogenous
base
O
O
Phosphate
C
C
O
C
Deoxyribose
15
One Strand of DNA
nucleotide
• One strand of DNA
is a polymer of
nucleotides.
• One strand of DNA
has many millions
of nucleotides.
16
Four nitrogenous bases
DNA has four different bases:
• Cytosine
C
• Thymine T
• Adenine A
• Guanine G
17
Two Stranded DNA
• Remember, DNA
has two strands
that fit together
something like a
zipper.
• The teeth are the
nitrogenous
bases but why
do they stick
together?
18
C
N
N
C
N
N
C
C
C
O
• The bases attract each
other because of
hydrogen bonds.
• Hydrogen bonds are weak
but there are millions and
millions of them in a
single molecule of DNA.
• The bonds between
cytosine and guanine are
shown here with dotted
lines
N
Hydrogen Bonds
N
C
N
C
C
O
19
C
N
Hydrogen Bonds, cont.
• When making
hydrogen bonds,
cytosine always
pairs up with
guanine
• Adenine always
pairs up with
thymine
• Adenine is bonded
to thymine here
O
N
O
C
C
C C
N
C
20
Chargaff’s Rule: Base
Pairing Rule
• Adenine and Thymine
always join together
A
T
• Cytosine and Guanine
always join together
C
G
21
DNA by the Numbers
• Each cell has about 2 m
of DNA.
• The average human has
75 trillion cells.
• The average human has
enough DNA to go from
the earth to the sun
more than 400 times.
• DNA has a diameter of
only 0.000000002 m.
The earth is 150 billion m
or 93 million miles from
the sun.
22
What have we learned about DNA
so far?
• 1. DNA is made of units called _________.
• 2. A sugar and a _______ make up the sides of the
DNA ladder?
• 3. DNA is found in the ____ of a eukaryotic cell.
• 4. If a one strand of DNA is: ATCCGTAAG. What is
the complementary strand?
• 5. What three scientists won the Nobel prize in
medicine for their discovery of DNA’s structure?
• 6. What is the process where viruses reproduce
called?
What have we learned about DNA
so far?
• 1. DNA is made of units called
__nucleotides__.
• 2. A sugar and a _______ make up the sides
of the DNA ladder?
What have we learned about DNA
so far?
• 1. DNA is made of units called
__nucleotides__.
• 2. A sugar and a __phosphate_ make up the
sides of the DNA ladder?
• 3. DNA is found in the ____ of a eukaryotic
cell.
What have we learned about DNA
so far?
• 1. DNA is made of units called
__nucleotides__.
• 2. A sugar and a __phosphate_ make up the
sides of the DNA ladder?
• 3. DNA is found in the _nucleus_ of a
eukaryotic cell.
• 4. If a one strand of DNA is: ATCCGTAAG.
What is the complementary strand?
What have we learned about DNA
so far?
• 1. DNA is made of units called __nucleotides__.
• 2. A sugar and a __phosphate_ make up the sides
of the DNA ladder?
• 3. DNA is found in the _nucleus_ of a eukaryotic
cell.
• 4. If a one strand of DNA is: ATCCGTAAG. What is
the complementary strand? TAGGCATTC
• 5. What three scientists won the Nobel prize in
medicine for their discovery of DNA’s structure?
What have we learned about DNA
so far?
• 1. DNA is made of units called __nucleotides__.
• 2. A sugar and a __phosphate_ make up the sides of the
DNA ladder?
• 3. DNA is found in the _nucleus_ of a eukaryotic cell.
• 4. If a one strand of DNA is: ATCCGTAAG. What is the
complementary strand? TAGGCATTC
• 5. What three scientists won the Nobel prize in medicine for
their discovery of DNA’s structure?
Watson, Crick and Wilkins
• 6. What is the process where viruses reproduce called?
What have we learned about DNA
so far?
• 1. DNA is made of units called __nucleotides__.
• 2. A sugar and a __phosphate_ make up the sides of the
DNA ladder?
• 3. DNA is found in the _nucleus_ of a eukaryotic cell.
• 4. If a one strand of DNA is: ATCCGTAAG. What is the
complementary strand? TAGGCATTC
• 5. What three scientists won the Nobel prize in medicine for
their discovery of DNA’s structure?
Watson, Crick and Wilkins
• 6. What is the process where viruses reproduce called?
The Lytic Cycle
30
RNA & Protein Synthesis
© Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved
Chromosome Structure of Eukaryotes
Nucleosome
Chromosome
DNA
double
helix
Coils
Supercoils
Histones
Nucleosomes pack together to form thick
coiled fibers. When cell is NOT dividing,
these fibers are spread out in nucleus as
CHROMATIN (Allows reading of code)
___________.
Image from: http://evolution.berkeley.edu/evosite/evo101/images/dna_bases.gif
HOW IS DNA COPIED?
The structure of DNA
explains how it can be
copied.
Each strand has all the info
needed to construct
matching
the __________other
half.
If strands are separated,
base-pairing rules allow
_____________
you to fill in the
complementary bases.
Figure 12–11 DNA Replication
Section 12-2
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Original
strand
Nitrogenous
bases
Sites where strand separation and
replication forks
replication occur are called _____________
REPLICATION STEPS
1.Enzymes “unzip” molecule by breaking
_______________
Hydrogen bonds that hold the strands
together and unwind it.
DNA polymerase joins nucleotides
2. _______________
using original strand as template and
spell checks
______________for
errors.
opposite directions
3. Copying happens in ________
along the two strands & in __________
multiple
places at once.
DNA Replication
• DNA replication occurs before every cell in
the body divides.
• Every cell in the body has the exact same
DNA (except for sex cells)
• Replication occurs in the S stage of the
Interphase part of cell division or (Mitosis)
REPLICATION
ANIMATION
See a video clip about
DNA REPLICATION (12B)
ACTIVITY
• BE A DNA MOLECULE
DNA
• Semi-conservative
means that you
conserve part of
the original
structure in the
new one.
• You end up with 2
identical strands of
DNA.
Replication Quiz
A---?
G---?
C---?
2. When does replication occur?
T---?
3. Describe how replication works. A---?
G---?
A---?
4. Use the complementary rule to
G---?
create the complementary
C---?
strand:
A---?
G---?
T---?
1. Why is replication necessary?
Replication Quiz
1. Why is replication necessary?
So both new cells will have the correct
DNA
2. When does replication occur?
3. Describe how replication works.
4. Use the complementary rule to
create the complementary strand:
A--G--C--T--A--G--A--G--C--A--G--T---
Replication Quiz
1. Why is replication necessary?
So both new cells will have the correct
DNA
2. When does replication occur?
During interphase (S phase).
3. Describe how replication works.
4. Use the complementary rule to
create the complementary strand:
A--G--C--T--A--G--A--G--C--A--G--T---
Replication Quiz
A---T
1. Why is replication necessary?
G---C
So both new cells will have the correct
C---G
DNA
T---A
2. When does replication occur?
A---T
During interphase (S phase).
G---C
3. Describe how replication works.
A---T
Enzymes unzip DNA and complementary G---C
nucleotides join each original strand.
C---G
4. Use the complementary rule to
A---T
create the complementary strand:
G---C
T---A
DNA
• Gene - a segment of
DNA that codes for a
protein, which in turn
codes for a trait (skin
tone, eye color, etc.)
• A gene is a stretch of
DNA.
DNA
• A mistake in DNA
replication is called a
mutation.
• Many enzymes are
involved in finding and
repairing mistakes.
• Mutagen: An agent, such as a chemical,
ultraviolet light, or a radioactive element,
that can induce or increase the frequency
of mutation in an organism. (Almost
anything that you can think of that causes
cancer is a mutagen.)
Mutations
• A change in DNA sequence
• A mistake that’s made during replication,
translation, transcription or cell division
• Can be:
harmful: disease deformities
helpful: organism better able to survive
neutral: organism unaffected
If a mutation occurs in a sperm or egg cell, that mutation is
passed to the offspring, if a mutation occurs in a body or
somatic cell it only affect the organism and is not passed
on to the offspring.
Mutations
• Example: Sickle Cell Anemia
When can having
the sickle cell trait
be an advantage?
Mutations
• Example: Hemophilia
DNA Repair
• A complex system of
enzymes, active in the G2
stage of interphase,
serves as a back up to
repair damaged DNA
before it is dispersed into
new cells during mitosis.
RNA
Phosphate
Group
O
O=P-O
O
Nitrogenous base
(A, U , G, C )
5
CH2
O
N
Sugar
(ribose)
C4
C3
C1
C2
RNA
• Function: obtain
information from
DNA & synthesizes
proteins
3 differences from DNA
1. Single strand
instead of double
strand
2. Ribose instead of
deoxyribose
3. Uracil instead of
thymine
3 types of RNA
1. Messenger RNA (mRNA)copies information from DNA
for protein synthesis
Codon- 3 base pairs that
code for a single amino
acid.
codon
3 types of RNA
2. Transfer RNA (tRNA)collects amino acids for
protein synthesis
Anticodon-a sequence
of 3 bases that are
complementary base
pairs to a codon in the
mRNA
3 types of RNA
3. Ribosomal RNA (rRNA)combines with proteins to form
ribosomes
Amino Acids
• Amino acids- the
building blocks of
protein
• At least one kind of tRNA
is present for each of the
20 amino acids used in
protein synthesis.
Transcription - mRNA is made from DNA
& goes to the ribosome
Translation - Proteins are made from the
message on the mRNA
Transcription
• In order for cells to make
proteins, the DNA code
must be transcribed
(copied) to mRNA.
• The mRNA carries the
code from the nucleus to
the ribosomes.
Occurs in the nucleus
Translation
• At the ribosome,
amino acids (AA)
are linked together
to form specific
proteins.
• The amino acid
sequence is
directed by the
mRNA molecule.
Amino acids
ribosome
Make mRNA ---Transcription
DNA
RNA
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence ????
Make mRNA ---Transcription
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence
UAC
Make mRNA ---Transcription
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence
UAC UUU
Make mRNA ---Transcription
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence
UAC UUU UUG
Make mRNA ---Transcription
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence
UAC UUU UUG UUC
Make mRNA ---Transcription
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence
UAC UUU UUG UUC CAU
Make mRNA ---Transcription
• DNA sequence
• ATG AAA AAC AAG GTA TAG
• mRNA sequence
UAC UUU UUG UUC CAU AUC
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
___ ____ ____ ____ ____ ____
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC AAG
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC AAG GUA
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC AAG GUA UAG
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC AAG GUA
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC AAG GUA
Make a Protein
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
tRNA sequence (anti- codon)
AUG AAA AAC AAG GUA
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr Phe
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr Phe
Leu
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr Phe
Leu Phe
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr Phe
Leu Phe Hist
Make Protein (amino acids)
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr Phe
Leu Phe Hist
Iso
Make mRNA
• mRNA sequence (codon)
UAC UUU UUG UUC CAU AUC
Tyr
Phe Leu Phe Hist Iso
Amino Acid sequence --- Protein
Human Genome Project
•
The Human Genome Project is a
collaborative effort of scientists around the
world to map the entire gene sequence of
organisms.
•
This information will be useful in detection,
prevention, and treatment of many genetic
diseases.
DNA Technologies
• DNA technologies
allow scientists to
identify, study, and
modify genes.
• Forensic identification
is an example of the
application of DNA
technology.
Gene Therapy
• Gene therapy is a technique for correcting
defective genes responsible for disease
development.
• Possible cures for:
– diabetes
– cardiovascular disease
– cystic fibrosis
– Alzheimer's
– Parkinson’s
– and many other diseases is possible.
Genetic Engineering
•
•
The human manipulation of the genetic
material of a cell.
Recombinant DNA- Genetically
engineered DNA prepared by splicing
genes from one species into the cells of
a different species. Such DNA becomes
part of the host's genetic makeup and is
replicated.
Genetic Engineering
•
Genetic engineering techniques are used in
a variety of industries, in agriculture, in
basic research, and in medicine.
This genetically
engineered cow
resists infections of
the udders and can
help to increase dairy
production.
Genetic Engineering
•
There is great potential for the development
of useful products through genetic
engineering
•
EX., human growth hormone, insulin, and pestand disease-resistant fruits and vegetables
Seedless
watermelons are
genetically
engineered
Genetic Engineering
•
We can now grow new body parts and soon
donating blood will be a thing of the past,
but will we go too far?
Photo of a mouse
growing a "human ear"
1. Why is transcription necessary?
2.
3.
4.
5.
Describe transcription.
Why is translation necessary?
Describe translation
What are the main differences between
DNA and RNA?
6. Using the chart on page 211, identify the
amino acids coded for by these codons:
UGGCAGUGC
1. Why is transcription necessary?
2.
3.
4.
5.
6.
Transcription makes messenger RNA (MRNA)
to carry the code for proteins out of the
nucleus to the ribosomes in the cytoplasm.
Describe transcription.
Why is translation necessary?
Describe translation
What are the main differences between DNA
and RNA?
Using the chart on page 211, identify the
amino acids coded for by these codons:
UGGCAGUGC
1. Why is transcription necessary?
Transcription makes messenger RNA (MRNA)
to carry the code for proteins out of the
nucleus to the ribosomes in the cytoplasm.
2. Describe transcription.
RNA polymerase binds to DNA, separates the
strands, then uses one strand as a template to
assemble MRNA.
3. Why is translation necessary?
4. Describe translation.
5. What are the main differences between DNA
and RNA?
1. Why is transcription necessary?
Transcription makes messenger RNA (MRNA)
to carry the code for proteins out of the
nucleus to the ribosomes in the cytoplasm.
2. Describe transcription.
RNA polymerase binds to DNA, separates the
strands, then uses one strand as a template to
assemble MRNA.
3. Why is translation necessary? DNA cannot
leave the nucleus, so mRNA carries the
message.
4. Describe translation.
4. Describe translation.
The cell uses information from MRNA to
produce proteins.
5. What are the main differences between
DNA and RNA.
6. Using the codon chart, identify the amino
acids coded for by these codons:
UGGCAGUGC
4. Describe translation.
The cell uses information from MRNA to
produce proteins.
5. What are the main differences between
DNA and RNA.
DNA has deoxyribose, RNA has ribose;
DNA has 2 strands, RNA has one strand;
DNA has thymine, RNA has uracil.
6. Using the codon chart, identify the amino
acids coded for by these codons:
UGGCAGUGC
4. Describe translation.
The cell uses information from MRNA to
produce proteins.
5. What are the main differences between
DNA and RNA.
DNA has deoxyribose, RNA has ribose;
DNA has 2 strands, RNA has one strand;
DNA has thymine, RNA has uracil.
6. Using the codon chart, identify the amino
acids coded for by these codons:
UGGCAGUGC
tryptophan-glutamine-cysteine
If a strand of DNA is 30% Adenine,
then what percentage of the cell is:
Thymine –
Guanine-
Cytosine -
DNA
strand
A
G
T
A
T
G
T
T
G
T
A
A
G
C
T
Replicate
DNA
DNA Replicate DNA strand
strand
DNA
T
G
A
A
T
G
A
C
C
T
C
A
G
T
A
C
C
G
T
A
G
C
A
G
C
T
T
A
G
C
Replicate
DNA