DNA-The code of life

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DNA-The code of life

• Why dont we all look alike?

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WARM-UP 7
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Why do we Study DNA?

1. Disease
2. Better vegetable, fruit, and animals.
3. Crime
4. History of life

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DNA Facts

• One chromosome has 50 - 250
• million base pairs.
• DNA is found in the mitochondria.
• mDNA is only found in the egg. Sperm
• has no mitochondria so mDNA is passed
• to offspring from the mother.
• One sequence of DNA is a genome or
• gene.
• Unwind all our DNA, it will stretch from the moon
• and back 6000X.

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http//public.ornl.gov/hgmis/gallery/
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• 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.
• What is the human genome?

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Genetic material of cells

• GENES units of genetic material that CODES FOR
  A SPECIFIC TRAIT
• Called NUCLEIC ACIDS
• DNA is made up of repeating monomers called
  NUCLEOTIDES

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DNA(Deoxyribonucleic Acid)
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A HISTORY OF DNA

• Discovery of the DNA double helix
• A. Frederick Griffith Discovers that a factor
  in diseased bacteria can transform harmless
  bacteria into deadly bacteria (1928)
• B. Rosalind Franklin - X-ray photo of DNA.
• (1952)
• C. Watson and Crick - described the DNA
  molecule from Franklins X-ray.
• (1953)

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Discovery of DNA
Invented X-ray diffraction photography. Photo
used to determine the shape of DNA is spiral.
Rosalind Franklin -
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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.
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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

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DNA
DNA stands for
Deoxyribonucleic acid
Functions of DNA 1. Carries the codes to make
proteins.

1. Carries the genetic material that is passed on
   from the parents to the offspring.

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STRUCTURE OF DNA
These three parts form the basic unit of DNA
called the NUCLEOTIDE.
phosphate
Nitrogen base Can be A, T, C or G
Sugar (deoxyribose)
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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)
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STRUCTURE OF DNA
Nitrogen Bases (Steps of the ladder) -

• Adenine - A
• Thymine T
• Cytocine C
• Guanine - G

The bases are connected to the sugar only !!!!!
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DNA Nucleotide

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phosphate
adenine
sugar
thymine
cytocine
guanine
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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.

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DNA
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DNA Double Helix

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Nitrogenous Bases

• PURINES
• 1. Adenine (A)
• 2. Guanine (G)
• PYRIMIDINES
• 3. Thymine (T)
• 4. Cytosine (C)

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BASE-PAIRINGS

• 2 Bonds

3 bonds
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STRUCTURE OF DNA
One complete turn of the double helix is 10 base
pairs or 10 steps on the ladder
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DNA Double Helix

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Chargaffs Rule

• Adenine must pair with Thymine
• Guanine must pair with Cytosine
• Their amounts in a given DNA molecule will be
  about the same.

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Chargaffs Rule

• Chargaff discovered that the percentage of A and
  T were equal. The same for C and G. This
  observation became Chargaffs rule. This is
  always the same no matter what organisms.

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Video of girl burned!!

• United streaming

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Genetic Diversity

• Different arrangements of NUCLEOTIDES in a
  nucleic acid (DNA) provides the key to DIVERSITY
  among living organisms.

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The Code of Life

• The code of the chromosome is the SPECIFIC
  ORDER that bases occur.
• A T C G T A T G C G G

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DNA is wrapped tightly around histones and coiled
tightly to form chromosomes
See p. 297
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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.
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Watson and Crick

• The model that Watson and Crick where the
  nitrogen bases pair suggested a mechanism for
  DNA to replicate.

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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 contained half of the old.

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STEPS OF DNA REPLICATION
1. Helicase begin to unzip the double helix at
many different places. The hydrogen bonds
between the bases are broken. Occurs in two
different directions.
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.
This results in 2 new identical DNA molecules.
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DNA Replication Video http//www.youtube.com/watc
h?vzdDkiRw1PdUfeatureplayer_embedded
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DNA Replication Fork
Point where DNA is split apart to replicate.
Forms a Y!
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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!

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DNA Replication in Prokaryotic Cells

• 1. Proteins binds to starting point.
• 2. Starts at a single point and proceeds in both
  directions.

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Eukaryotic Replication

• Since eukaryotic cells are so much bigger, the
  replication will start at dozens to hundreds of
  different places on the DNA.

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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.
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DNA Fingerprinting

• When DNA is found at a crime, the DNA is
  replicated many times to make enough to test.
  Once they have fingerprinted it, they can compare
  to find suspect.
• Video
• http//www.bing.com/videos/search?qdnacrimescen
  eviewdetailmid684167203C024AD0C797684167203C02
  4AD0C797first21FORMLKVR22adltstrict

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DNA Fingerprinting
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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.

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Transciption Making of RNA

• Transcription process of copying DNA to produce
  a complimentary strand of RNA.

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Types of RNA
There are three (3) types RNA
1. Messenger RNA (mRNA) carries messages from
the DNA in the nucleus to the cytoplasm.
2. Transfer RNA (tRNA) 20 different kinds
which are only able to bond with one (1) specific
type of amino acid.
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Types of RNA

• 3. Ribosomal RNA (rRNA) major component (part)
  of the ribosomes

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RNA TRANSCIPTION
Transcription the process by which DNA makes
RNA.
Steps in RNA Transcription

1. A special enzyme tells DNA its time to make RNA.
2. The enzyme tells the nucleotides to only bond
   with RNA nucleotides.
3. The code letters for RNA are A, C, G and U.

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RNA TRANSCIPTION

• 4. Process occurs just like DNA replication
• When complete, only a single strand of RNA is
  formed UNLIKE DNAs double strand.
• All three types of RNA are formed this way.
• 7. All leave the nucleus and travel out into the
  cytoplasm.

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RNA TRANSLATION
Protein Synthesis the formation of a protein
using information coded on DNA and carried out by
RNA in the assembly of amino acids.

• Proteins are
• Amino acids in chains 20 kinds
• Made of 10s or 100s or 1000s of amino acids
• Must be arranged in a specific sequence for each
  type of protein
• Function type of protein is determined by amino
  acid sequence
• DNA makes RNA
• RNA constructs amino acids

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RNA TRANSLATION
Translation Process

• MRNA goes to the ribosomes, tRNA
• goes to the cytoplasm.
• 2. tRNA picks up amino acids brings them
• to the ribosome.
• 3. mRNA tells tRNA in which sequence to
• assemble the proteins.
• 4. An amino acid chain is a protein.

SO
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RNA TRANSLATION
So WHAT??
RNA makes amino acid chains
DNA makes RNA
Amino acid chains make proteins
Proteins make cells
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Go to gslc.genetics.utah.edu/units Translate
Transcribe a Protein and What is a Protein?
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We have been told that DNA is the blueprint for
life, BUT what does that mean?
DNA holds the instructions that tell a cell how
to construct amino acid chains.
SO WHAT?
Proteins build cells
That is important because amino acid chains build
proteins.
AND
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Steps to Protein Synthesis

• 1. DNA replication make new DNA
• 2. Transcription DNA message given to RNA
• 3. Translation RNA is translated in amino acid
  chains(protein).

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Prokaryotic - Protein synthesis

• Location cytoplasm
• At the same time.
• Eukaryotic Protein synthesis

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SO, HOW DOES AN AMINO ACID CHAIN GET BUILT?
Well, first we have to make something called RNA
RNA stands for ribonucleic acid
It differs from DNA in three ways
1. RNA is single stranded.
2. The sugar in RNA is called ribose.

1. Uracil is one of the bases in RNA. There is NO
   thymine in RNA. This means A goes with U and G
   still goes with C.

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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

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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.

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Semiconservative Model

• Replication is called semiconservation because
  one strand of DNA is used to as a template to
  make the new DNA.

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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.
• .

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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.

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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.

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Replication Quiz

• 1. Why is replication necessary?
• 2. When does replication occur?
• 3. Describe how replication works.
• Use the complementary rule to
• create the complementary strand

A---? G---? C---? T---? A---? G---? A---? G---? C-
--? A---? G---? T---?
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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.
• Enzymes unzip DNA and complementary nucleotides
  join each original strand.
• 4. Use the complementary rule to
• create the complementary strand

A---T G---C C---G T---A A---T G---C A---T G---C C-
--G A---T G---C T---A
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(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.

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DNA Transcription

• DNA can unzip itself and RNA nucleotides match
  up to the DNA strand.
• Both DNA RNA are formed from NUCLEOTIDES and
  are called NUCLEIC acids.

See p.301
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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
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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

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• 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.

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• 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.
• Using the chart on page 303, identify the amino
  acids coded for by these codons UGGCAGUGC
• tryptophan-glutamine-cysteine

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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)

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LETS REVIEW DNALM 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?