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Chapter 8 The Central Dogma of Molecular Biology

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Chapter 8 The Central Dogma of Molecular Biology Cell DNA Transcription Ribosome mRNA Translation ... DNA REPLICATION Process in which DNA is copied. – PowerPoint PPT presentation

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Title: Chapter 8 The Central Dogma of Molecular Biology


1
Chapter 8The Central Dogma of Molecular Biology
Cell
2
  • DNA (DEOXYRIBONUCLEIC ACID)
  • Nucleic acid that composes chromosomes and
    carries genetic information.

3
  • CHROMOSOME ORGANIZATION
  • 1. A chromosome is an enormous strand of super
    coiled DNA.
  • 2. Sections of DNA on the chromosome that code
    for proteins are called genes.
  • 3. Noncoding sections of DNA are called junk
    DNA (regulatory or unknown function)

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  • BUILDING BLOCKS OF DNA
  • Composed of nucleotides
  • Nucleotides contain three parts
  • 1. 5-Carbon Sugar (deoxyribose)
  • 2. Phosphate Group
  • 3. Nitrogen Base (four types, adenine, guanine,
    thymine and cytosine)

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  • Adenine and Guanine are purines (composed of two
    rings of nitrogen atoms)

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  • Thymine and Cytosine are pyrimidines (composed of
    one ring of nitrogen atoms)

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  • STRUCTURE OF DNA
  • Consists of two strands of nucleotides that form
    a twisted ladder (double helix)
  • Sugar and phosphate alternate along the sides of
    the ladder (linked by strong covalent bonds)
  • Pairs of nitrogen bases form the rungs of the
    ladder (linked by weak hydrogen bonds).

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  • Specific base pairing arrangement (Chargaffs
    Rule)
  • A-T 2 hydrogen bonds
  • C-G 3 hydrogen bonds
  • Nitrogen bases attach to the sugar portion of the
    side (NOT the phosphate)
  • Strands run in opposite directions

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  • FUNCTION OF DNA
  • DNA codes for proteins (structural proteins,
    enzymes, and hormones)
  • information for building proteins is carried in
    the sequence of nitrogen bases
  • proteins determine physical and metabolic traits
    and regulate growth and development.

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  • DNA REPLICATION
  • Process in which DNA is copied.
  • PURPOSE OF DNA REPLICATION
  • Gives daughter cells produced by cell division a
    complete set of genetic information identical to
    the parent cell.
  • WHERE REPLICATION OCCURS
  • Nucleus
  • WHEN DURING THE CELL CYCLE REPLICATION OCCURS
  • Interphase (S)

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  • HOW REPLICATION OCCURS
  • 1. Helicase enzymes unzip the parent strand by
    separating the nitrogen base pairs.
  • 2. DNA polymerase pairs free DNA nucleotides
    with the exposed bases on both strands following
    the base pair rules.
  • each strand from the parent molecule serve as a
    template

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  • 3. Hydrogen bonds reform spontaneously sealing
    the two strands of each DNA molecule together.

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  • RESULTS OF REPLICATION
  • Two molecules of DNA that are identical
  • Each is half old (strand from parent) and half
    new (strand synthesized by DNA polymerase)

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  • RNA (RIBONUCLEIC ACID)
  • Nucleic acid involved in the synthesis of proteins

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  • RNA STRUCTURE
  • Composed of nucleotides, but differs from DNA in
    three ways.
  • Single strand of nucleotides instead of double
    stranded
  • Has uracil instead of thymine
  • Contains ribose instead of deoxyribose

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  • DNA RNA
  • Double strand Single strand
  • A---Thymine A---Uracil
  • Deoxyribose Ribose

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  • RNA FUNCTION
  • Three forms of RNA involved in protein synthesis
  • 1. mRNA (messenger) copies instructions in DNA
    and carries these to the ribosome.
  • 2. tRNA (transfer) carries amino acids to the
    ribosome.
  • 3. rRNA (ribosomal) composes the proteins
    (ribosome).

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  • PROTEIN SYNTHESIS
  • Cells build proteins following instructions coded
    in genes (DNA).
  • Consists of two parts, transcription and
    translation

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  • TRANSCRIPTION
  • DNA is copied into a complementary strand of
    mRNA.
  • WHY?
  • DNA cannot leave the nucleus. Proteins are made
    in the cytoplasm. mRNA serves as a messenger
    and carries the protein building instructions to
    the ribosomes in the cytoplasm.

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  • LOCATION OF TRANSCRIPTION
  • Nucleus
  • HOW TRANSCRIPTION OCCURS
  • 1. RNA polymerase untwists and unzips a section
    of DNA (usually a single gene) from a chromosome.

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  • 2. RNA polymerase pairs free RNA nucleotides to
    the exposed bases of one of the DNA strands
    following base pair rules.
  • Uracil replaces thymine
  • Only 1 strand of DNA serves as a template, the
    other hangs out
  • 3. Newly synthesized mRNA separates from
    template DNA and DNA zips back up.

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Protein Synthesis Transcription
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  • RESULT OF TRANSCRIPTION
  • mRNA strand with instructions for building a
    protein that leaves the nucleus and goes to the
    cytoplasm.

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  • TRANSCRIPTION EXAMPLE
  • Transcribe the following DNA Sequence in mRNA
  • TAC CGG ATC CTA GGA TCA
  • AUG GCC UAG GAU CCU AGU

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  • PROTEINS
  • Structural and functional components of
    organisms.
  • Composed of amino acids (monomers).
  • order of nucleotides in DNA determines order of
    amino acids in a protein
  • One gene codes for one protein

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  • GENETIC CODE
  • The language that translates the sequence of
    nitrogen bases in DNA (mRNA) into the amino acids
    of a protein.
  • Codon three nucleotides on DNA or mRNA
  • One codon specifies one amino acid
  • Some codons are redundant (code for the same
    amino acid)
  • The genetic code is universal to all organisms

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  • TRANSLATION
  • Instructions in mRNA are used to build a protein

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  • PROCESS OF TRANSLATION
  • 1. mRNA binds to the ribosome.
  • 2. Ribosome searches for start codon (AUG)
  • 3. tRNA brings correct amino acid (methionine)
    to the ribosome.
  • Each tRNA carries one type of amino acid.
  • The anticodon (three nitrogen bases on tRNA) must
    complement codon for amino acid to be added to
    protein chain

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  • 4. ribosome reads next codon
  • 5. tRNAs continue lining up amino acids
    according to codons
  • 6. peptide bonds link amino acids together
  • 7. ribosome reaches STOP codon
  • Amino acid chain is released

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  • LOCATION OF TRANSLATION
  • ribosome (in the cytoplasm)
  • RESULT OF TRANSLATION
  • A Protein

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Protein Synthesis Translation
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A Codon
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Protein Synthesis Translation
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Protein Synthesis Translation
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Translation - Initiation
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Translation - Elongation
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Translation - Elongation
Aminoacyl tRNA
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  • DNA TAC CTT GTG CAT GGG ATC
  • mRNA AUG GAA CAC GUA CCC UAG
  • A.A MET G.A HIS VAL PRO STOP

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  • IMPORTANT CODONS
  • AUG start translation (Met)
  • UAA, UAG, UGA stop translation
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