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DNA
CLIP
1
DNA
• located in the
nucleus
• Function: Carry
genetic material
• Many People
contributed to
the discovery of
DNA.
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People Who Discovered DNA
• 1928 – Frederick Griffith
- DNA = carrier of genetic
info
• 1944 – Avery – Genes =
composed of DNA
• 1952 – Hershey and
Chase – genetic material =
DNA, not protein
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People Who Discovered DNA
• 1952 – Rosalind Franklin –
DNA = twisted
• 1952 – Edwin Chargraff #A = #T; #C = #G;
Chargraff’s Rule
• 1953 – Watson and Crick –
Discovered structure of
DNA we know today
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Shape of DNA
1. Double Helix.
-Twisted ladder or
spiral staircase
2. Two stranded
3. Held together by
hydrogen bonds
4. Made of four
Nucleotides
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Structure of DNA
Remember:
• DNA is a
nucleic
acid.
• Nucleic
acids are
made of
nucleotides
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Nucleotides
• DNA = long chain
of nucleotides
• 4 that make up
DNA
• Have 3 parts: a
sugar molecule
(deoxyribose), a
phosphate group,
and a
nitrogenous base
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4
Nitrogenous
Bases
•
•
•
•
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Adenine
Guanine
Cytosine
Thymine
Sides of
the
“Ladder”
are made
up of
sugar and
phosphate.
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Adenine always pairs with Thymine
Cytosine always pairs with Guanine
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Would
Thymine
be able
to pair
up with
Guanine?
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DNA
Replication
• Before mitosis,
the DNA must be
replicated (Copied)
exactly.
• Each strand can
be used to make
the other strand.
• Many enzymes are
involved.
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Chromosome
Structure
• DNA is packed very tightly
as chromosomes in the
nucleus.
• Human nucleus has 1 meter
of DNA!
• Smallest human
chromosome has 30 million
base pairs.
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Chromosome
Structure
• A chromosome has
DNA and proteinchromatin.
• Tiny sections of
DNA are called
genes
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Steps:
Semi-conservative replication
1. parent/original
strands are
unwound with the
help of DNA
helicases
(enzymes).
Replication Bubble
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Steps:
2. DNA
polymerase
attached
new
nucleotides
to the
parent
strands
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DNA replication website
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How a protein is
made
•Transcription
•Translation
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DNA codes for all of the
cell proteins.
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Overview:
• DNA is located in the Nucleus
• Proteins are made on the ribosomes.
• DNA makes a copy (send a message) called “mRNA”
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Two Steps of Protein Synthesis
1. Transcription
2. Translation
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Transcription
• a copy of the DNA is made…the copy is
called messenger RNA or mRNA.
• The mRNA takes the code to the
ribosome.
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DNA vs. RNA
• Double
Stranded
• AGTC
• Deoxyribose
• NEVER!
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• Single
Stranded
• AGUC
• Ribose
• YES!
DNA Transcription
• During transcription the DNA unzipped and
RNA nucleotide are paired up with the DNA
bases.
• Website
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• Once the mRNA copy is made, it can
go to the ribosome to be translated.
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• Remember
….Proteins
are made
out of
amino
acids.
• There are
20
different
amino
acids.
• 3 bases
code for
each amino
acid =
codon.
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How you
figure out
which codon is
coding for
which amino
acid…
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• Once the mRNA
gets to the
ribosome, the
protein can be
assembled.
• Transfer RNA
brings the amino
acids to the
ribosome.
• Website
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• The three letter code on the mRNA is
called a codon.
• The three letter code on the tRNA that is
matched up with the mRNA is called an
anticodon.
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Review Clip
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Mutations
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Mutations
• A sudden change in the genetic
code is called a mutation.
• Most mutations have little or no
effect on the organism.
• Mutations can be spontaneous or
may be caused by environmental
factors called mutagens.
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Mutations in DNA usually occur through one
of three processes:
1- DNA damage from environmental agents such as
ultraviolet light (sunshine) or nuclear radiation
Certain chemicals called mutagens
2- Errors that occur when a cell replicates its DNA in
preparation for cell division.
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Types of
Mutations
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Point
mutation
-a simple change
in a single base
of the gene
sequence
- 3 Types:
1. Point
2. Insertion
3. Deletion
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Frame-shift
Mutations
In a frame-shift
mutation, one or
more bases are
deleted or inserted,
the equivalent of
adding or removing
letters in a sentence.
Original:
THE CAT ATE THE RAT
Deletion:
THE CAT ATE THE RAT
THE CTA TET HER AT
Insertion
THE CAT ATE THE RAT
THE CAT ATT ETH ERA T
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Chromosomal Mutations
• Mutations can occur that involve whole or
partial chromosomes
– Non-disjunction – homologous chromosomes
don’t separate during meiosis – a gamete ends
up with an extra chromosome (ex. Down’s
syndrome)
– Crossing Over – parts of homologous
chromosomes are swapped during meiosis
43A
Results of DNA Mutations
• The results of mutations can be
• Helpful
– They can result in a helpful trait such as better
camoflage
CLIP
• Neutral
– If the mutation does not cause a change in
amino acid sequence, or the replaces 1 amino
acid with one that is similar, the protein will still
function the same.
• Harmful
– A large change in the amino acid sequence51
can
make a protein that does not function at all.
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Which of the following
is the correct basepairing rule for DNA?
A A-U; C-G
B A-G; T-C
C A-T; G-C
D A-C; T-G
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DNA
TECHNOLOGY
genetic recombination.
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DNA Fingerprinting
Determining the sequence of bases in
DNA for comparisons
How they identify criminals and do
paternity tests (i.e. “Who is my Baby’s
Daddy?”)
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•
•
•
•
How DNA Fingerprinting works:
Scientist cut up DNA into pieces using enzymes
Then load the pieces into a gel.
Electricity is run through the gel.
The pieces of DNA move to the other end of the gel.
Smaller pieces move farther.
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Who doesn’t belong?
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Recombinant DNA
•is a form of artificial DNA where
DNA combined that would not
normally be combined.
•They cut, splice together, and
insert the modified DNA molecules
from different species into bacteria
or another type of cell that rapidly
replicates and divides.
•The cells copy the foreign DNA
right along with their own DNA.
•Example: goldfish have genes for
fluorescent proteins that have been
inserted
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Genetic Engineering
•the manipulation of an organisms
genes
•applications in medicine and the
environment, industry, and
agriculture.
•Sheep are used in the production
of alpha-1 antitrypsin, which is
used in the treatment of
emphysema.
•Goats are also producing the CFTR
protein used in the treatment of
cystic fibrosis.
•Crops are being devised that have
natural insect repellants
•60
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Genetic Engineering
Example:
In the plant world, the buds of cotton
plants are vulnerable to worm
attacks. The buds of a modified
cotton plant resist these worms,
resulting in increased cotton
production.
These gene insertions are
ecologically safer than pesticides.
They affect only the targeted pest.
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Clip
Scientists today have developed genetically
altered bacteria.
Among them are strains of bacteria that
eat up oil spills
manufacture alcohol and other
chemicals
process minerals.
There is concern about possible risks to the
environment and the general population as
genetically engineered bacteria are
introduced.
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Cloning
• Occurs when the DNA from an adult is inserted into
the fertilized egg of the organism.
• Results in an offspring that is genetically identical
to the parent.
• The DNA in the egg must be removed before the
new DNA is inserted.
• Has been used in animals and plants, hopes for the
future to allow for the cloning of organs.
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