DNA

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Chapter 10

• DNA

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10.1 Discovery of DNA

• Griffiths Experiments (1928)
• Griffiths experiments showed that hereditary
  material can pass from one bacterial cell to
  another.
• The transfer of genetic material to one cell from
  another cell or from one organism to another
  organism is called transformation.

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Averys Experiments (1940s)

• Averys work showed that DNA was the heredity
  material that transfers information between
  bacterial cells.

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Hershery-Chase Experiment

• Hershey and Chase confirmed that DNA, and not
  protein, is the hereditary material.
• Page 195

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Structure of DNA

• 10.2

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DNA The Blueprint of Life

• Established by James Watson and Francis Crick
  (1950s)
• DNA contains the instructions for making proteins
  within the cell.
• Shape of a double helix
• Made up of repeating sub-units called nucleotides

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DNA codes for genes

• Gene - A segment of DNA that codes for a protein,
  which in turn codes for a trait (skin tone, eye
  coloretc.), a gene is a stretch of DNA.

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Deoxyribonucleic acid - DNA

• Monomer nucleotides
• Each nucleotides has
• Deoxyribose sugar
• Phosphate group
• (1 of 4) nitrogen containing base

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The 4 Bases in DNA are

• Thymine (T)
• Cytosine (C)
• Guanine (G)
• Adenine (A)

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Nitrogen Rings

• Purines have double rings of carbon-nitrogen (G,
  A)
• Pyrimidines have single carbon-nitrogen rings (C,
  T)

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Complementary Base Pairing

• Base Pairing Rules
• 1. C and G
• 2. T and A

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Hydrogen Bonds

• How do the nitrogenous bases stick together?
• Hydrogen bonds
• 3 H bonds hold G C together
• 2 H bonds hold T A together

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DNA Replication 10.3

• Occurs when chromosomes duplicate before mitosis
  meiosis
• Makes an exact copy of the DNA
• H bonds between bases break and enzymes unzip
  the molecule

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Steps of DNA Replication (pg. 201)

• Enzymes called helicases separate the DNA strand
  breaking the H bonds at the replication fork
• Enzymes called DNA polymerase add complementary
  nucleotides
• DNA polymerase falls off when done replicating
  and the result is an
• identical strand of DNA

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Semi-conservative replication-Each old strand of
nucleotides serves as a template for each new
strand.
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Another View of Replication
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Protein Synthesis

• 10.4

The Central Dogma the flow of genetic
information from DNA to RNA to Protein
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Protein Synthesis

• 2 Parts
• Transcription makes a RNA molecule
  complementary to a portion of DNA.
• Translation occurs when the sequences of bases
  of mRNA directs the sequence of amino acids in a
  polypeptide.

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RNA

• Ribonucleic Acid
• 2nd type of nucleic acid
• Monomer nucleotide
• Ribose sugar
• 1 of 4 N bases
• Phosphate group

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N-bases

• A, G, C, U
• Uracil replaces Thymine
• Base pairing rules A-U, G-C
• Purpose to transfer genetic material from DNA
  (inside the nucleus) to the site of protein
  synthesis (in the cytoplasm)

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How does RNA differ from DNA?

1. Different sugars (deoxyribose vs. ribose)
2. Different N-bases (thymine vs. uracil)
3. Different shapes (double helix vs. single strand)

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Types of RNA

• Messenger RNA (mRNA)
• Carries genetic info from the nucleus to the
  cytoplasm
• Transfer RNA (tRNA)
• Carries specific amino acids to the ribosome to
  build the protein
• Ribosomal RNA (rRNA)
• Major component of the ribosome organelle
• Site of protein synthesis
• Most abundant type of RNA

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3 Types of RNA
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How is RNA made?

• Transcription
• The process by which RNA is copied from DNA in
  the nucleus

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Steps of Transcription

1. RNA polymerase binds to the promoter section of
   DNA
2. DNA unwinds and separates
3. RNA polymerase adds nucleotides complimentary to
   the DNA template strand
4. Process ends once RNA polymerase reaches the
   termination signal on the DNA

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Definitions

• RNA polymerase enzyme use to make an RNA polymer
  from DNA
• Promoter Starting point on DNA
• DNA template Strand of DNA that RNA is
  complementary to (create from)
• Termination signal Ending point on DNA

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Products of Transcription

• mRNA, tRNA, rRNA
• All products move out of the nucleus and go into
  the cytoplasm to be used in protein synthesis

DNA ? RNA
mRNA tRNA rRNA
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Protein Synthesis

• The making of proteins at the ribosome
• The amount and kind of proteins produced in a
  cell determine its structure function
• Proteins carry out the genetic instruction in DNA

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Protein Review

• Monomer amino acids
• 20 different types
• Linked together by peptide bonds
• Sequence of amino acids determines the proteins
  structure and function

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The Genetic Code

• The correlation between nucleotide sequence (DNA
  or RNA) and amino acid sequence (protein)
• Codons combination of 3 mRNA nucleotides that
  code for a specific amino acid

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Types of codons

• 64 codons code for 20 amino acids
• Thus more than one codon codes for an AA
• Start codon (AUG) starts the process of
  translation
• Stop codons (UAA, UAG, UGA) ends the process of
  translation

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Circular Genetic Code
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Translation

• The process of assembling polypeptides (proteins)
  from nucleotide sequence in mRNA
• Translating from one language (nucleotides)
  into another language (amino acids)

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Steps of Translation

• During translation, amino acids are assembled
  from information encoded in mRNA
• As mRNA codons move through the ribosome, tRNAs
  add specific amino acids to the growing
  polypeptide chain.
• The process continues until a stop codon is
  reached and the newly made protein is released.

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So what is the Central Dogma?

• The flow from DNA to RNA to Protein

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Mutation

• A change in the nucleotide sequence of a DNA
  molecule.
• DNA proofreading and repair prevent many
  replication errors.
• Unrepaired mutations that affect genes that
  control cell division can cause diseases such as
  cancer.

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Notebook Quiz

1. What type of RNA is pictured here? What is its
   function?
2. List the 4 bases in RNA?
3. What is the function of mRNA?
4. Define translation.
5. Where are proteins assembled in the cell?
6. Describe the flow of genetic material in the
   cell. In other words, how do cells make proteins?