Download DNA - Warren County Schools

Why do we Study DNA?
1.
2.
3.
4.
Disease
Better vegetable, fruit, and animals.
Crime
History of life
• DO YOU UNDERSTAND
THE RELATIONSHIP
BETWEEN A GENE, DNA,
AND
CHROMOSOMES????????
• DNA: nucleic acid that builds
chromosomes.
• Gene: segment of DNA on your
chromosomes that determines your
traits.
• Trait: characteristics about you. It can
be a part or a behavior. You inherited
your traits from your parents.
Remember BB, Bb,or bb!!
• Chromosomes: 23 pairs made up of
DNA wind around histones (proteins).
• What is the human genome?
DNA Karotype – Appearance of the chromosome
of a somatic cells. Paired in descending size.
Karotype
• A display of metaphase
chromosomes of a cell arranged by
size and centromere positions.
• From these pictures, doctors can
study to chromosomes to look for
disorders.
DNA Facts
•One chromosome has 50 – 250 million base
pairs(A,T,C,AND G). This is why we are all
different!!!
•DNA is found in the mitochondria.
One sequence of DNA is a genome or gene.
*DNA molecules are incredibly long.
If all of the DNA from all of your cells
was stretched out into a single thread, it
would extend to the moon and back
about one million times!
• The human genome is contained in 23
pairs of chromosomes.
• The DNA within the human genome
makes up 60,000 to 100,000 genes.
The nucleus, or control centre, of a cell, is
where DNA is located.
http://genomics.energy.gov/gallery/chromosomes/gallery-01.html
Discovery of DNA
Invented X-ray
Rosalind
diffraction
Franklin - photography. Photo
used to determine the
shape of DNA is
spiral.
DISCOVERY OF DNA
James Watson and
Francis Crick used the
information from
Franklin and other
scientists to build a 3-D
model of DNA.
Won the Nobel
Piece Prize in
Chemistry in 1961.
Watson & Crick proposed…
•DNA had specific pairing between the
nitrogen bases:
ADENINE – THYMINE
CYTOSINE – GUANINE
•DNA was made of 2 long stands of
nucleotides arranged in a specific
way called the “Complementary Rule”
A HISTORY OF THE STRUCTURE
OF DNA
• Discovery of the DNA double helix
A. Rosalind Franklin - Used X-ray
photo of DNA to discover the shape
was a double helix.
(1952)
B. Watson and Crick - Used
Franklin’s work to build the first model
of DNA. They figured out the exact
structure.
(1953)
Why Do You
Think We All
Are
Different????
DNA – stands for!!!
(Deoxyribonucleic Acid)
DNA
DNA stands for – Deoxyribonucleic acid
Functions of DNA:
1. Carries the codes
to make proteins.
2.Carries the genetic
material that is passed
on from the parents to
the offspring.
DNA Double Helix – SHAPE!!!
“Rungs of ladder”
Nitrogenous
Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone
STRUCTURE OF DNA
These three parts the basic unit of
DNA NUCLEOTIDE(monomer).
phosphate
Sugar
(deoxyribose)
Nitrogen base
Can be A, T, C or G
DNA Nucleotide
Phosphate
Group
O
O=P-O
O
5
CH2
O
N
C1
C4
Sugar
(deoxyribose)
C3
C2
Nitrogenous base
(A, G, C, or T)
STRUCTURE OF DNA
Side Pieces(The Rope Part)
Are alternating units of a 5
carbon sugar and a
phosphate group. These
go down both sides of the
molecule
phosphate
Sugar (called deoxyribose)
STRUCTURE OF DNA
Nitrogen Bases (Steps of the ladder)
1.Adenine - A
2.Thymine
–T
2
.
3.Cytocine – C
4.Guanine - G
The bases are
connected to
the sugar
only !!!!!
Nitrogenous Bases
• PURINES – double ring
1. Adenine (A)
2. Guanine (G)
A or G
• PYRIMIDINES – single ring
3. Thymine (T)
4. Cytosine (C)
T or C
BASE-PAIRINGS
H-bonds
3 bonds
G
C
T
A
2 Bonds
phophate
adenine
sugar
thymine
cytocine
guanine
How are the nucleotides held
together?
• Nucleotides are
held together by
covalent bonds
between the sugar
of one nucleotide
and the phosphate
of the next.
DNA
Amount of DNA
• Amount of DNA in a sample can be
determined by how much UV light is
absorbs. DNA absorbs UV light!!!
STRUCTURE OF DNA
One complete
turn of the
double helix is
10 base pairs
or 10 steps on
the ladder
DNA is antiparallel
The two strand of DNA run opposite of each
other. The happens because of the
structure of the nitrogen bases. To fit
together,they must be upside down.
DNA Double Helix
5
O
3
3
O
P
5
O
C
G
1
P
5
3
2
4
4
2
3
1
P
T
5
A
P
3
O
O
P
5
O
3
5
P
Chargaff’s Rule
• Adenine must pair with Thymine
• Guanine must pair with Cytosine
• Their amounts in a given DNA molecule will be
about the same.
T
A
G
C
Chargaff’s Rule
• In his experments on several different
organisms, Chargaff discovered that the
percentage of A and T were equal. The
same for C and G. This observation
became Chargaff’s rule. This is always
the same no matter what organisms.
Genetic Diversity…
• Different
arrangements of
NUCLEOTIDES in a
nucleic acid (DNA)
provides the key to
DIVERSITY among
living organisms.
What makes us all different?
Our alphabet!!!!
• The “code” of the chromosome is the
SPECIFIC ORDER that bases occur.
A T C G T A T G C G G…
How does our DNA fit into the nucleus?
DNA is wrapped tightly around
histones and coiled tightly to form
chromosomes
Why extract DNA?
• To show there is DNA in the food we eat.
• TO show how much DNA there is in a
small piece of banana
• To show where DNA is located in
organisms.
• To discuss the function of DNA.
• To demonstrate how to remove DNA from
organism
What Happens to the DNA in
the foods we eat?
• Our digestive system will break it down
into nucleotides we can use.
• It can be broken down into even smaller
parts of phoshate, sugars, and nitrogen.
Video of girl burned!!
• United streaming
Watson and Crick
• The model that Watson and Crick where
the nitrogen bases pair suggested a
mechanism for DNA to replicate.
Messelson and Stahl
• They proved that DNA is semiconservative
by attaching radioactive material to DNA.
As the cell divided, they observed the new
DNA in each cell and saw that it contain
half of the old.
How does DNA copy itself?
Purpose: DNA copies itself to ensure
that each new cell that is produced in
gets the correct number of
chromosomes and receives an EXACT
copy of the DNA molecule.
This is called DNA REPLICATION.
The DNA molecule serves
as its own pattern or
template so as an exact
copy can be made.
DNDA Replication
• DNA must copy itself so each new cell has
a copy so you can –
• GROW
• REPAIR
STEPS OF DNA REPLICATION
•
Helicase begin to unzip the double helix at many
different places breaking the hydrogen bonds
between the bases creates a replication fork.
Occurs in two different directions.
Leading strand – read normal
Lagging strand – upside down – reads in fragments
Okazaki Fragments
This occurs in many places along the DNA!!
Sites of replication – places where replication is
occurring
Okazaki Fragments
Small segments of DNA that are used on the
3’ DNA. DNA ligase puts them together.
2.
Free floating in the cytoplasm
nucleotides pair with the bases on
the template. DNA polyermase
bonds together the nucleotides.
Small segments are bonded
together.
3. Two identical strands of DNA
result. The DNA will twist back
together. DNA is called
SEMICONSERVATIVE because
it uses an old strand to make a
new one.
4. DNA polymerase – checks for
mistakes – PROOFREADS!!!
DNA Replication Fork
Point where DNA is split apart to
replicate. Forms a Y!
Semi-conservative
• DNA replication is said to be semiconservative because it uses an old
strand to create a new one.
Role of Enzymes
1. Helicase unzips the
two DNA strands.
2. DNA polymerase is
the enzyme that joins
individual nucleotides
to produce a new
strand of DNA.
Proofreads DNA
when finished!
3. Ligase -links together
the 3’ DNA strand
DNA Replication in Prokaryotic
Cells
1. Proteins binds to
starting point.
2. Starts at a single
point and proceeds
in both directions.
Eukaryotic Replication
• Since eukaryotic cells
are so much bigger,
the replication will
start at dozens to
hundreds of different
places on the DNA.
DNA REPLICATION
What if there is a
mistake?
There is always a
chance that the wrong
nucleotide bonds to
another. HOWEVER,
DNA polymerase is
responsible for
“reading” the bases
and recognizing and
replacing damaged or
wrong nucleotides.
This PROOFREADING
allows for only one (1)
error in ONE BILLION
nucleotides.
DNA Fingerprinting
• When DNA is found at a crime crime, the
DNA I replicated many time to make
enough to test. Once they have
fingerprinted it, they can compare to find
suspect.
Go to DNA replication
animation
www.fed.cuhk.edu.hk/~johnson/teaching/genetics/
animations/dna_replication.htm
http://video.search.yahoo.com/
search/video;_ylt=Anvp.VTwI60W.
BKoUEpJxR.
bvZx4?p=dna+replication&toggle=
1&cop=mss&ei=UTF-8&fr=yfp-t-701
DNA Fingerprinting
Speed of DNA Replication
• In the human cell, 50 nucleotides can
be added every second. It would that
several days for replication to occur if
the DNA did not start at several spots
on the DNA so that it is occurring in
many places on the DNA strand.
DNA Replication
• Replication: coping of DNA
• The DNA molecule produces 2
IDENTICAL new complementary
strands following the rules of
base pairing:
A-T, G-C
•Each strand of the
original DNA serves as
a template for the new
strand
Why is DNA Replication
necessary?
• DNA must copy
itself so that each
new cell gets a
copy of DNA.
Replication must
occur before cell
division.
Semiconservative Model
• Replication is called semiconservation
because one strand of DNA is used to as a
template to make the new DNA.
Steps of DNA
Replication
1.DNA unzips and the
hydrogen bonds between
the nitrogen bases pulled
apart. The base pairs are
separated and are left
exposed. This occurs in
two different directions.
This occurs along
hundreds of different
places at a time.
.
DNA Template
Parental DNA
New DNA
Steps of Replication
2. Free-floating
nucleotides are
paired up to the
free nucleotides.
DNA polymerase
bond the
nucleotides
together.
3.Two identical
strands result.
DNA polymerase
checks for
mistakes when
complete.
DNA Replication
• DNA has 80 million base pairs in a
chromosomes. DNA is copied at about 50
base pairs per second. This would take a
month if replication did not occur at hundreds
of different places at once.
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
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
(1961)
Watson & Crick proposed…
• …DNA controlled cell function by
serving as a template for PROTEIN
structure.
• 3 Nucleotides = a triplet or CODON
(which code for a specific AMINO ACID)
See p.303
• AMINO ACIDS are the building blocks
of proteins.
DNA Transcription
• DNA can “unzip”
itself and RNA
nucleotides match
up to the DNA
strand. See p.301
• Both DNA & RNA
are formed from
NUCLEOTIDES and
are called NUCLEIC
acids.
DNA Translation
• The cell uses
information from
“messenger” RNA
to produce proteins
See p.304-305
We will
discuss details
of this on a
later date
1.
2.
3.
4.
5.
6.
Transcription/Translation Quiz
Why is transcription necessary?
Describe transcription.
Why is translation necessary?
Describe translation.
What are the main differences
between DNA and RNA.
Using the chart on page 303,
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?
Translation assures that the right amino acids
are joined together by peptides to form the
correct protein.
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 chart on page 303, identify the
amino acids coded for by these codons:
UGGCAGUGC
tryptophan-glutamine-cysteine
AMAZING DNA FACTS…
• DNA from a single human
cell extends in a single
thread for almost 2 meters
long!!!
• It contains information
equal to some 600,000
printed pages of 500 words
each!!!
(a library of about 1,000 books)
LET’S REVIEW DNA…
LM p.44
1. List the conclusions Griffith & Avery,
Hershey & Chase drew from their
experiments.
2. Summarize the relationship between
genes & DNA.
3. Describe the overall structure of the
DNA molecule.
4. What are the 4 kinds of bases?
MUTATIONS
Changes in DNA that affect genetic
information
Gene Mutations
• Point Mutations – changes in
one or a few nucleotides
– Substitution
• THE FAT CAT ATE THE RAT
• THE FAT HAT ATE THE RAT
– Insertion
• THE FAT CAT ATE THE RAT
• THE FAT CAT XLW ATE THE RAT
– Deletion
• THE FAT CAT ATE THE RAT
• THE FAT ATE THE RAT
Gene Mutations
• Frameshift Mutations – shifts
the reading frame of the
genetic message so that the
protein may not be able to
perform its function.
– Insertion
• THE FAT CAT ATE THE RAT
• THE FAT HCA TAT ETH ERA T
– Deletion
H
• THE FAT CAT ATE THE RAT
• TEF ATC ATA TET GER AT
H
Sex Chromosome Abnormalities
• XYY Syndrome
– Normal male traits
– Often tall and thin
– Associated with antisocial and behavioral
problems
Chromosome Mutations
• Changes in number and structure of entire
chromosomes
• Original Chromosome ABC * DEF
• Deletion
AC * DEF
• Duplication
ABBC * DEF
• Inversion
AED * CBF
• Translocation
ABC * JKL
GHI * DEF
Significance of Mutations
• Most are neutral
• Eye color
• Birth marks
• Some are harmful
• Sickle Cell Anemia
• Down Syndrome
• Some are beneficial
• Sickle Cell Anemia to Malaria
• Immunity to HIV
What Causes Mutations?
• There are two ways in which DNA can
become mutated:
– Mutations can be inherited.
• Parent to child
– Mutations can be acquired.
• Environmental damage
• Mistakes when DNA is copied
Chromosome Mutations
• Down Syndrome
– Chromosome 21 does
not separate correctly.
– They have 47
chromosomes in stead of
46.
– Children with Down
Syndrome develop
slower, may have heart
and stomach illnesses
and vary greatly in their
degree of inteligence.
Chromosome Mutations
• Cri-du-chat
– Deletion of material on 5th
chromosome
– Characterized by the cat-like
cry made by cri-du-chat
babies
– Varied levels of metal
handicaps
Sex Chromosome Abnormalities
• Klinefelter’s
Syndrome
–
–
–
–
–
XXY, XXYY, XXXY
Male
Sterility
Small testicles
Breast enlargement
Sex Chromosome Abnormalities
• XYY Syndrome
– Normal male traits
– Often tall and thin
– Associated with antisocial and behavioral
problems
Sex Chromosome Mutations
• Turner’s Syndrome
–X
– Female
– sex organs don't
mature at adolescence
– sterility
– short stature
Sex Chromosome Mutations
• XXX
– Trisomy X
– Female
– Little or no visible differences
– tall stature
– learning disabilities
– limited fertility
How do we know that all of our
genetic information comes from
DNA?
• What type of experiment would you
design to determine that DNA is the
source of all genetic information?
After Mendal? WHAT CARRIES
THE TRAITS TO OFFSPRING?
• They did not know what carried the genes.
• Scientists actually thought that proteins
carries the genetic code.
• Several scientists worked to disprove this
theory.
Scientists – Proved DNA carries
genetic code not proteins
1. Griffith
2. Avery
3. Hershey and Chase
Fredick Griffith’s Experiment
1. Injected mice with two bacteria - one that
made them sick and one that didn’t.
2. He boiled bacteria A and then the mice
did not get sick.
3. He injected both bacteria A(boiled) and
bacteria B into mice and they got sick.
CONCLUDED - Transformation occurred.
Bacteria causing bacteria changed the
harmless bacteria. Passed on genes
somehow.
Griffith’s Experiment with Pneumonia
and the accidental discovery of
Transformation
• Frederick Griffiths was a
bacteriologist studying
pneumonia
• He discovered two types of
bacteria:
– Smooth colonies
– Rough colonies
Griffith’s Experiment with Pneumonia
and the accidental discovery of
Transformation
CONCLUSION:
The smooth colonies
must carry the disease!
Griffith’s Experiment with Pneumonia
and the accidental discovery of
Transformation
• When heat was applied
to the deadly smooth
type…
• And injected into a
mouse…
• The mouse lived!
Griffith’s Experiment with Pneumonia
and the accidental discovery of
Transformation
• Griffith injected the heat-killed
type and the non-deadly rough
type of bacteria.
• The bacteria “transformed” itself
from the heated non-deadly type
to the deadly type.
Avery, McCarty, and MacLeod
Repeated Griffith’s Experiment
Oswald Avery
Maclyn McCarty
Colin MacLeod
Avery, McCarty, and MacLeod
Repeated Griffith’s Experiment
Avery, McCarty, and MacLeod
Added the non-deadly Rough Type of
Bacteria to the Heat-Killed Smooth Type
To the Heat-Killed Smooth Type,
added enzymes that destroyed…
Carbohydrates
Lipids
Proteins
RNA
DNA
S-Type
S-Type
S-Type
S-Type
S-Type
Carbohydrates Lipids
Proteins
RNA
DNA
Destroyed Destroyed Destroyed Destroyed Destroyed
Conclusion:
DNA was the
transforming factor!
The Hershey-Chase Experiment
Alfred Hershey &
Martha Chase
worked with a
bacteriophage:
A virus that
invades bacteria.
It consists of a
DNA core and a
protein coat
Protein coat
DNA
Protein coats of bacteriophages labeled with Sulfur-35
Phage
1. Hershey and Chase
Bacterium
mixed the
radioactively-labeled
viruses with the
bacteria
Phage
Bacterium
The viruses infect the
bacterial cells.
DNA of bacteriophages labeled with Phosphorus-32
Hershey - Chase
Injected bacteriophages with radioactive
isotopes then placed them with bacteria.
The virus injected the bacteria with DNA
containing radioactive material. Then
tested for the radioactive material.
COCNLUDED: Viruses passed on their
DNA to the bacteria.
The Hershey-Chase results
reinforced the Avery, McCarty, and
MacLeod conclusion:
DNA carries the genetic code!
However, there were still
important details to uncover…
WHAT is the structure of DNA????