DNA

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DNA Protein Synthesis
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History

• Before the 1940s scientists didnt know what
  material caused inheritance.
• They suspected it was either DNA or proteins.

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History

• A series of experiments proved that DNA was the
  genetic material responsible for inheritance.

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History

• In 1952, Alfred Hershey and Martha Chase did an
  experiment using a virus that infects E. coli
  bacteria.
• The experiment proved that DNA and not protein is
  the factor that influences inheritance.

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History

• Erwin Chargaff discovered the base pairing rules
  and ratios for different species.
• Adenine pairs with Thymine
• Cytosine pairs with Guanine.

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History

• Rosalind Franklin Maurice Wilkins had taken the
  1st pictures of DNA using X-ray crystallization

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This proved that DNA had a helical shape.
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History

• The Nobel Prize in Medicine 1962

Francis Harry Compton Crick
James Dewey Watson
Rosalind Franklin (Died of cancer 1958)
Maurice Hugh Frederick Wilkins
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Wilkins has become a historical footnote and
Watson Crick are remembered as the Fathers of
DNA
Double Helix
Watson
Crick
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DNA
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Nitrogen Bases

• 2 types of Nitrogen Bases
• Purines
• Double ring
• G A
• Pyrimidines
• Single ring
• C U T

PGA
CUT PY
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DNA - double helix
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DNA

• The genetic code is a sequence of DNA nucleotides
  in the nucleus of cells.

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DNA

• DNA is a double-stranded molecule.
• The strands are connected by complementary
  nucleotide pairs (A-T C-G) like rungs on a
  ladder.
• The ladder twists to form a double helix.

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DNA

• During S stage in interphase, DNA replicates
  itself.
• DNA replication is a semi-conservative process.

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DNA

• Semi-conservative means that you conserve part of
  the original structure in the new one.
• You end up with 2 identical strands of DNA.

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DNA

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

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DNA

• A mistake in DNA replication is called a
  mutation.
• Many enzymes are involved in finding and
  repairing mistakes.

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Mutations

• What causes mutations?
• Can occur spontaneously
• Can be caused by a mutagen
• Mutagen An agent, such as a chemical,
  ultraviolet light, or a radioactive element, that
  can induce or increase the frequency of mutation
  in an organism.

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Mutations

• Some mutations can
• Have little to no effect
• Be beneficial (produce organisms that are better
  suited to their environments)
• Be deleterious (harmful)

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Mutations

• Types of mutations
• Point Mutations or Substitutions causes the
  replacement of a single base nucleotide with
  another nucleotide
• Missense- code for a different amino acid
• Nonsense- code for a stop, which can shorten the
  protein
• Silent- code for the same amino acid (AA)

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Mutations

• Example Sickle Cell Anemia

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Mutations

• Types of mutations
• Frame Shift Mutations the number of nucleotides
  inserted or deleted is not a multiple of three,
  so that every codon beyond the point of insertion
  or deletion is read incorrectly during
  translation.
• Ex. Crohns disease

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Insertion
Deletion
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Mutations

• Types of mutations
• Chromosomal Inversions an entire section of DNA
  is reversed.
• Ex. hemophilia,
• a bleeding disorder

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DNA Repair

• A complex system of enzymes, active in the G2
  stage of interphase, serves as a back up to
  repair damaged DNA before it is dispersed into
  new cells during mitosis.

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RNA
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RNA

• Function obtain information from DNA
  synthesizes proteins

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3 differences from DNA

1. Single strand instead of double strand
2. Ribose instead of deoxyribose
3. Uracil instead of thymine

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3 types of RNA

• Messenger RNA (mRNA)- copies information from DNA
  for protein synthesis
• Codon- 3 base pairs that
• code for a single amino
• acid.

codon
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3 types of RNA

• 2. Transfer RNA (tRNA)- collects amino acids for
  protein synthesis
• Anticodon-a sequence of 3 bases that are
  complementary base pairs to a codon in the mRNA

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3 types of RNA

• 3. Ribosomal RNA (rRNA)- combines with proteins
  to form ribosomes

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DNA Replication

• During DNA replication, the DNA molecule
  separates into 2 strands, and then produces 2 new
  complementary strands following the rules of base
  pairing.
• Each strand of the double helix of DNA serves as
  a template, or model, for the new strand.
• http//207.207.4.198/pub/flash/24/menu.swf

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Amino Acids

• Amino acids- the building blocks of protein
• At least one kind of tRNA is present for each of
  the 20 amino acids used in protein synthesis.

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Transcription - mRNA is made from DNA goes to
the ribosome Translation - Proteins are made from
the message on the mRNA           
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Transcription

• In order for cells to make proteins, the DNA code
  must be transcribed (copied) to mRNA.
• The mRNA carries the code from the nucleus to the
  ribosomes.
• http//www-class.unl.edu/biochem/gp2/m_biology/ani
  mation/gene/gene_a2.html

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Translation

• At the ribosome, amino acids (AA) are linked
  together to form specific proteins.
• The amino acid sequence is directed by the mRNA
  molecule.
• http//www-class.unl.edu/biochem/gp2/m_biology/ani
  mation/gene/gene_a3.html

Amino acids
ribosome
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Make A Protein

• DNA sequence
• ATG AAA AAC AAG GTA TAG

• mRNA sequence

UAC UUU UUG UUC CAU AUC
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Make mRNA

• mRNA sequence
• UAC UUU UUG UUC CAU AUC
• tRNA sequence

AUG AAA AAC AAG GUA UAG