DNA AND RNA

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CHAPTER 12

• DNA AND RNA

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• Sutton and Boveri
• Formulated the chromosome theory of heredity in
  1903
• Fredrick Griffith
• Helped determine that genes are composed of DNA
• Experimented with Streptococcus pneumoniae
  (bacteria) in mice

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• Two strains used
• S because it looked smooth and caused pneumonia
• R because it looked rough and did not cause
  pneumonia
• Griffith injected mice with heat-killed S strains
  and they did not get pneumonia
• Griffith injected a mixture of heat-killed S and
  healthy R and the mice got pneumonia

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• Griffiths experiment

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• Griffith reasoned that a material must have been
  transferred from the heat-killed S strain to the
  R strain
• 1944 Avery discovered that it was DNA

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• Chase and Hershey
• Found that DNA was without a doubt the substance
  that was the hereditary material
• Used bacteria and viruses called bacteriophages

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• Watson and Crick
• Found the components of the nucleotides
• And that sugar and phosphate formed the sides
  of the helix
• Franklin
• Photographed DNA using X rays and found that DNA
  was spiral shaped

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• DOUBLE HELIX twisted ladder
• Sides of ladder
• Alternating sugar and phosphates
• Rungs of ladder
• Chargaffs rules
• Pairs of bases
• ( A T or G C)
• Adenine
• Thymine
• Cytosine
• Guanine
• Held together by hydrogen bonds

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• Chargaff
• Found that the four bases always paired in a
  certain way
• Adenine always pairs with thymine
• Guanine always pairs with cytosine
• Two classes of nitrogen bases
• Pyrimidines cytosine and thymine
• Purines adenine and guanine

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• DNA structure
• Made up of smaller units called nucleotides
• Nucleotide
• One phosphate
• One sugar (deoxyribose)
• One nitrogen base

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• DNA REPLICATION
• DEF making another copy of DNA
• Done during synthesis of interphase
• Done in order to insure all cells in body have
  same information

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• DNA replication
• Makes a copy of itself during mitosis and meiosis
• ANIMATION LINK

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• STEPS IN DNA REPLICATION
• Double helix is opened by a specific enzyme by
  breaking open hydrogen bonds between bases
• Free nucleotides are base paired according to A-T
  and G-C by enzyme called DNA polymerase pairs up
  bases

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• Another enzyme causes the hydrogen bonds to form
  new rungs again and another enzyme causes
  sugar-phosphate bonds form to create new side
• Resulting in two new identical DNA molecules
  each have one original side and one new side

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• CHROMOSOMES AND DNA
• Chromosomes made of protein and DNA
• One type of protein histone
• DNA wraps around histones twice
• Nucleosome one histone and its DNA

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• Histones are important in keeping the DNA in
  order as it tightens and becomes a chromosome
  before mitosis

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CHAPTER 12.1

• Protein synthesis
• Process by which an organisms genotype is
  translated into its phenotype
• Involves two types of nucleic acids
• DNA
• RNA
• The order of the bases in DNA specifies order of
  bases in mRNA ? the order of amino acids (brought
  in by tRNA) ? makes the specific protein

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• PROTEINS ARE IMPORTANT
• Structure, repair, and growth
• As enzymes control metabolism
• Hormones steroids control growth and
  development
• RNA ribonucleic acid
• mRNA messenger RNA takes information for
  protein to be made from DNA to the ribosome

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• tRNA carries amino acids to ribosomes, lines
  them up in the correct order according to mRNA
• rRNA makes up the structure of the ribosome
• Monomers (RNA nucleotides) of RNA are composed of
  phosphate, ribose (sugar) and a base (adenine,
  guanine, cytosine and uracil)

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• DNA
• Double stranded
• Deoxyribose sugar
• Thymine pairs with adenine
• Located in the nucleus only

• RNA
• Single stranded
• Ribose sugar
• Uracil pairs with adenine
• Located all over the cell

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• Genes are made up of DNA
• The sequence of DNA bases in a gene determine the
  order of the amino acids making up a protein
• Every protein made in your body has a gene that
  codes for it.

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• TWO STEPS TO PROTEIN SYNTHESIS
• TRANSCRIPTION
• TRANSLATION

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• TRANSCRIPTION
• A copy of DNA is made by RNA polymerase
• Takes place in the nucleus
• A molecule of mRNA is formed that is
  complementary to the DNA
• transcribe means to copy (nucleic acid to
  nucleic acid)

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• TRANSCRIPTION
• Portion of the DNA that has the code for the
  needed protein opens up
• RNA polymerase separates the two strands of a DNA
  double helix
• RNA nucleotides are lined up across from the
  exposed bases on the sense strand according to
  Chargaffs rules by RNA polymerase

• DNA side used sense strand
• Other side nonsense strand

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• BASE PAIRS
• NONSENSE DNA - SENSE DNA mRNA G C G
• C G C
• A T A
• T A U
• 3 BASES OF DNA CODE
• 3 BASES OF mRNA triplet codon
• 3 BASES OF tRNA anticodon

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• Each triplet codon codes for one amino acid
• There are 64 possible codons
• Only 20 amino acids, therefore some amino acids
  may be coded for more than one triplet codon
• Initiator codon AUG ? codes for the amino acid
  methionine

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• Terminator codons UGA, UAG, UAA
• These are STOP codons and they signal the end of
  a protein

LET'S REVIEW!
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• The genetic instructions for a polypeptide chain
  are written in the DNA as a series of
  3-nucleotide words
• Codons
• U (uracil) replaces T in RNA

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• mRNA from nucleus is read along its codons by
  tRNAs anticodons at the ribosome
• tRNA anticodon (nucleotide triplet)
  amino acid

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• TRANSLATION
• DEF taking the message of mRNA and filling in
  the amino acids to make the protein
• Occurs at the ribosomes in the cytoplasm
• Once DNA makes the strand of mRNA, it leaves the
  nucleus and goes to the ribosome
• translate means to change languages (nucleic
  acid to protein)

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• The tRNA base pairs with the bases on the mRNA
  strand, bringing in the correct amino acids
• Peptide bonds form between the amino acids
  making a polypeptide which is a small protein (or
  part of a large protein)

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CHAPTER 12.1
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• BASE PAIRS
• NONSENSE DNA - SENSE DNA mRNA -tRNA
• G C G C
• C G C G
• A T A U
• T A U A
• Therefore DNA has controlled the production of
  the protein by bases paired with mRNA, which base
  paired with tRNA, nearly duplicated itself

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• Exons and introns go to end of notes
• Much of the mRNA that is transcribed in the
  nucleus does not actually get translated
• Some mRNA gets clipped out, enzymes do this
  called processing, maturing, or editing
• The part taken out introns (interferring)
• The part that actually codes for the needed
  protein and goes to the ribosome to be translated
  is called the exon (that which is expressed)

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http//omega.dawsoncollege.qc.ca/ray/protein/panim
.htm
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• Animation
• Another animation

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• PROKARYOTIC CELLS
• No nucleus
• mRNA travels right to the ribosome to begin
  translation

• EUKARYOTIC CELLS
• mRNA has to go through another step called RNA
  splicing
• Introns (noncoding segments of mRNA) are removed
• Exons (coding regions) are spliced together
• Then mRNA leaves the nucleus and goes to the
  ribosome

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• GENE MUTATIONS
• POINT MUTATIONS
• BECAUSE THEY OCCUR AT A SINGLE POINT IN THE DNA
  SEQUENCE
• DNA ? TAC GCA TGG AAT
• RNA ? AUG CGU ACC UUA
• AA ? MET-ART-THR-LEU
• BUT WHAT IF THERE IS A LETTER CHANGE?
• DNA ? TAC GTA TGG AAT
• WHAT IS THE CHANGE?
• RNA ? AUG CAU ACC UUA
• AA ? MET HIS- THR-LEU

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• FRAMESHIFT
• IF A NUCLEOTIDE IS DELETED OR INSERTED, BASES ARE
  STILL READ IN GROUPS OF THREE SO.
• DNA ? TAC GCA TGG AAT
• RNA ? AUG CGU ACC UUA
• AA ? MET- ARG- THR-LEU
• IF THERE IS AN INSERTION OF ONLY ONE NUCLEOTIDE
• DNA ? TAT CGC ATG GAA T
• RNA ? AUA GCG UAC CUU A
• AA ? ILE ALA- TYR-LEU

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• GENE REGULATION AND THE PROCESSING OF mRNA
• Genes can be turned off or on
• Activated or deactivated
• Activated means the gene is expressed or the
  protein is made
• Deactivated means the gene is not expressed or no
  protein is made

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• LAC OPERON
• DEF the set of DNA used to make lactase
• Consists of
• Three genes that code for lactase
• Promoter area in front of genes that says RNA
  polymerase start here
• Operator between promoter and genes where
  repressor sits when gene does not work

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• Repressor protein that when attached to
  operator stops production of gene
• If lactose is present in the bacteria it can act
  as the inducer (the inducer removes the
  repressor)
• Without the repressor sitting on the operator
• Lactase is made, lactase is the enzyme that
  breaks down lactose
• When the level of lactose in the cell gets low
  the repressor attaches to the operator

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CHAPTER 12.2

• JACOB AND MONOD
• Model of how bacterial cells (prokaryotes)
  control gene expression
• OPERON ?

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CHAPTER 12.2

• PROKARYOTIC CELLS
• Genes turn on and off in response to changes in
  the environment
• Example gene for lactase can be turned off by a
  molecule called a repressor

• EUKARYOTIC CELLS
• Only certain genes actually function
• Can control gene expression by controlling RNA
  splicing which results in one gene producing
  various proteins

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• DEVELOPMENT AND DIFFERENTIATION
• CELLS BECOME SPECIALIZED IN STRUCTURE AND
  FUNCTION
• HOX GENES
• SERIES OF GENES THAT CONTROL DIFFERENTIATION OF
  CELLS AND TISSUES
• MUTATION IN ONE OF THESE GENES CAN COMPLETELY
  CHANGE THE ORGANS THAT DEVELOP IN SPECIFIC PARTS
  OF THE BODY

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• GENE CALLED PAX 6
• CONTROLS EYE GROWTH IN MICE
• COPY OF THIS GENE WAS INSERTED INTO THE GENES
  THAT CONTROL THE GROWTH OF A FRUIT FLYS KNEE
  THE RESULTING FRUIT FLY GREW AN EYE ON ITS LEG!

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CHAPTER 14.3

• HUMAN DNA ANALYSIS
• TESTING FOR ALLELES
• DNA FINGERPRINTING
• ANALYSIS OF SECTIONS OF DNA
• SMALL SAMPLE IS CUT WITH A RESTRICTION ENZYME
  RESULTING IN FRAGMENTS OF VARYING LENGTH
• GEL ELECTROPHORESIS TO SEPARATE STRANDS BY LENGTH

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CHAPTER 14.3

• HUMAN GENOME PROJECT
• ANALYZE THE HUMAN DNA SEQUENCE
• GENE THERAPY
• AN ABSENT OR FAULTY GENE IS REPLACED BY A NORMAL
  WORKING GENE