DNA and RNA

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DNA and RNA

• Chapter 12

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Hereditary Material

• Genes are protein codes.
• Our genes are on our chromosomes.
• Chromosomes are made up of DNA.
• Genes are composed DNA!

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Chromosome Structure

• Chromatin is tightly coiled around proteins
  called histones.
• DNA and histone molecules form a beadlike
  structure nucleosome
• Nucleosomes create the supercoils
• of DNA in a chromosome.

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Chromosome Structure of Eukaryotes
Nucleosome
Chromosome
DNA double helix
Coils
Supercoils
Histones
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Structure of DNA

• In eukaryotes, DNA is found in the NUCLEUS of
  cells.
• DNA is made up of a series of monomers called
  nucleotides.
• Nucleotide structure
• 1. 5carbon sugar Deoxyribose
• 2. Phosphate group
• 3. Nitrogenous base
• DNA is a twisted-ladder called a
• DOUBLE HELIX!

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DNA Nucleotide

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Nitrogenous Bases

• Double ring PURINES
• Adenine (A)
• Guanine (G)
• Single ring PYRIMIDINES
• Thymine (T)
• Cytosine (C)

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Chargaffs (Base Pairing) Rule

• Adenine must pair with Thymine
• Guanine must pair with Cytosine
• The bases form weak hydrogen bonds

Why do they pair together this way?
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DNA Double Helix

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DNA Structure
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key Adenine (A) Thymine (T) Cytosine (C) Guanine
(G)
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DNA Replication

• Occurs during cell division.
• Helicase enzyme unzips the molecule of DNA,
  breaking the hydrogen bonds.
• Free-nucleotides in the nucleus will be bonded
  with its complementary base.
• DNA polymerase helps to bond the nucleotides
  together and check for errors.

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DNA Replication
Section 12-2
Original strand
DNA polymerase
New strand
Growth
DNA polymerase
Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand
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DNA Replication
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The Scientists

• Griffith one strain of bacteria was
  transformed into another strain.
• Avery found that DNA was the transforming
  factor.
• Hershey and Chase DNA is the genetic material.
• Watson and Crick discovered the molecular
  structure of DNA.

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Griffiths Transformation Experiment
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Averys experiment isolated the element that
caused the bacterial to become lethalDNA
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Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
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Chargaff and Franklin

• Chargaff
• Percentages of guanine and cytosine bases are
  almost equal in any sample of DNA
• Same is true of adenine and thymine
• DNA in all instances and from all organisms
  followed this rule
• Rosalind Franklin
• X-Ray diffraction showed that
• DNA was twisted into a
• double helix.

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RNA and Protein Synthesis

• Section 12-3

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RNA

• Long, single strand of nucleotides.
• Nitrogen bases A,U,G,C no Thymine!
• Sugar Ribose
• Found in cytoplasm and nucleus
• Types messenger, transfer, ribosomal
• Function Involved in the synthesis of protein
  molecules.

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Protein Synthesis occurs in two phases

• TRANSCRIPTION
• TRANSLATION

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Transcription

• Location where it occurs Nucleus
• RNA polymerase will unwind DNA at the region to
  be transcribed.
• It locates and binds at the promoter.

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• mRNA is then made by base-pairing
• A-U, G-C, T-A, C-G
• If DNA sequence is GATTACA
• Then mRNA sequence is CUAAUGU
• When finished, mRNA leaves the nucleus and goes
  to the cytoplasm.

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Transcription
Section 12-3
Adenine (DNA and RNA) Cystosine (DNA and
RNA) Guanine(DNA and RNA) Thymine (DNA
only) Uracil (RNA only)
RNApolymerase
DNA
RNA
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Translation

• Location Cytoplasm mRNA finds a ribosome
• Ribosome reads strand for the start codon
• A codon is a mRNA triplet. Ex AUG, UUC, etc
• Start codon is AUG
• Transfer RNAs bring
• amino acids to
• ribosome.

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Translation continued

• tRNAs anticodon bonds with mRNA codon.
• mRNA codons AUG UAA CGC
• tRNA anticodons UAC AUU GCG
• Amino acids connected with peptide bonds.
• When a Stop codon is reached. Protein is
  released from ribosome.

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Translation
Section 12-3
Animation
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How to Interpret m-RNAs Code

• Each 3 nitrogen base sequence is called a CODON.
• Each codon specifies for a particular amino acid.
• AUG codon starts the initiation of the protein
  and codes for the amino acid methionine.
• Stop codons do not code for any amino acids
  ending the protein chain.
• A polypeptide is a chain of amino acids joined
  with peptide bonds aka a PROTEIN!

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Codon Chart 1
Section 12-3
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Codon Chart 2
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Lets Practice!

• DNA TACTTGGAT
• mRNA AUGAACCUA
• tRNA UACUUGGAU
• Amino Acid squence
• Methionine, Asparagine, Leucine

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Mutations

• Section 12-4

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Mutations

• Changes that occur in the DNA
• Two types
• 1. Gene mutations
• 2. Chromosomal mutations
• Many mutations are harmless
• Pros increase adaptation or survival
• Cons some can be lethal or debilitating

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Gene Mutations

• Changes that occur in a single gene.
• Point mutations one nucleotide that affects one
  amino acid.
• (substitutions produce point mutations)
• Frameshift mutations involve the reading of the
  DNA or m-RNA strand many amino acids are
  affected.
• (insertion or deletions produce frameshift
  mutations)

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Gene Mutations
Frameshift mutations
Point mutation Substitution
Insertion
Deletion
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Chromosomal Mutations

• Whole chromosome is affected.
• Four types
• 1. Deletion loss of material
• 2. Duplication addition of material
• 3. Inversion rearrangement of material
• 4. Translocation switching material with
  another chromosome

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Chromosomal Mutations
Deletion
Duplication
Inversion
Translocation