DNA (Deoxyribonucleic Acid)

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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 Karotype
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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.
• Chromosomes 23 pairs made up of DNA wind around
  histones (proteins).
• What is the human genome?

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DNA Facts

• One chromosome has 50 - 250
• million base pairs.
• 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!

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• The human genome is contained in 23 pairs of
  chromosomes.
• The DNA within the human genome makes up 60,000
  to 100,000 genes.

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• .
• Humans get one complete set of genes from each
  parent.
• In April 2003, the National Human Genome
  Research Institute (NHGRI) celebrates
• the completion of the human genome sequence and
  the 50th anniversary of the description of the
  DNA double helix.
• The nucleus, or control centre, of a cell, is
  where DNA is located.

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http//genomics.energy.gov/gallery/chromosomes/gal
lery-01.html
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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.

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Genetic material of cells

• What is the type of organic molecule?
• Madeup of DNA
• Called NUCLEIC ACIDS
• DNA is made up of repeating monomers called
  NUCLEOTIDES

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DNA(Deoxyribonucleic Acid)
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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?

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Fredick Griffiths Experiment

• Injected mice with two bacteria - one that made
  them sick and one that didnt.
• He boiled bacteria A and then the mice did not
  get sick.
• 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.

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Griffiths 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

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Griffiths Experiment with Pneumonia and the
accidental discovery of Transformation
CONCLUSION The smooth colonies must carry the
disease!
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Griffiths 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!

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Griffiths 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.

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Avery, McCarty, and MacLeodRepeated Griffiths
Experiment
Oswald Avery
Maclyn McCarty
Colin MacLeod
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Avery, McCarty, and MacLeodRepeated Griffiths
Experiment
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Avery, McCarty, and MacLeodAdded 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
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S-Type Carbohydrates Destroyed
S-Type Lipids Destroyed
S-Type Proteins Destroyed
S-Type RNA Destroyed
S-Type DNA Destroyed
Conclusion DNA was the transforming factor!
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The Hershey-Chase Experiment
Protein coat

• Alfred Hershey Martha Chase worked with a
  bacteriophage
• A virus that invades bacteria. It consists of a
  DNA core and a protein coat

DNA
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Protein coats of bacteriophages labeled with
Sulfur-35
Phage

1. Hershey and Chase mixed the radioactively-labeled
   viruses with the bacteria

Bacterium
Phage
The viruses infect the bacterial cells.
Bacterium
DNA of bacteriophages labeled with Phosphorus-32
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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.

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The Hershey-Chase results reinforced the Avery,
McCarty, and MacLeod conclusion

• DNA carries the genetic code!

However, there were still important details to
uncover
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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 Franklins work to
  build the first model of DNA. They figured out
  the exact structure.
• (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 the basic unit of DNA
NUCLEOTIDE(monomer).
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

2.
The bases are connected to the sugar only !!!!!
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DNA Nucleotide

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phophate
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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Amount of DNA

• Amount of DNA in a sample can be determined by
  how much UV light is absorbs. DNA absorbs UV
  light!!!

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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 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.

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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

• 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 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 contain 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

1. DNA helicase breaks the hydrogen bonds between
   the two strands.
2. Replication occurs at multiple site along DNA
   called origins of replication. This will cause
   bubbles.
3. Replication occurs in both directions. This makes
   it quicker.
4. DNA polymerase bring in new nucleotides to fill
   match with old strand.

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• One strand is easily replicated, the other is
  made in pieces because DNA polymerase cannot read
  the upside down piece. DNA ligase will put the
  pieces together.
• DNA polyermase will work it way down DNA strands
  using old DNA as a template.
• Once complete DNA polyermase will proofread for
  mistakes.

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Go to DNA replication animation www.fed.cuhk.edu.h
k/johnson/teaching/genetics/ animations/dna_repli
cation.htm
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Okazaki Fragments

• Small segments of DNA that are used on the 3
  DNA. DNA ligase puts them together.

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ggle 1copmsseiUTF-8fryfp-t-701
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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!
• 3. Ligase -links together the 3 DNA strand

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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 crime, the DNA I
  replicated many time to make enough to test.
  Once they have fingerprinted it, they can compare
  to find suspect.

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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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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?

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MUTATIONS

• Changes in DNA that affect genetic information

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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

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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
• THE FAT CAT ATE THE RAT
• TEF ATC ATA TET GER AT

H
H
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Sex Chromosome Abnormalities

• XYY Syndrome
• Normal male traits
• Often tall and thin
• Associated with antisocial and behavioral problems

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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

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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

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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

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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.

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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

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Sex Chromosome Abnormalities

• Klinefelters Syndrome
• XXY, XXYY, XXXY
• Male
• Sterility
• Small testicles
• Breast enlargement

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Sex Chromosome Abnormalities

• XYY Syndrome
• Normal male traits
• Often tall and thin
• Associated with antisocial and behavioral problems

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Sex Chromosome Mutations

• Turners Syndrome
• X
• Female
• sex organs don't mature at adolescence
• sterility
• short stature

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Sex Chromosome Mutations

• XXX
• Trisomy X
• Female
• Little or no visible differences
• tall stature
• learning disabilities
• limited fertility

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