Nucleic Acids and protein synthesis

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Nucleic Acids and protein synthesis

• Higher Human Biology

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Lesson Aims

• To examine the structure of DNA
• To compare the structure of DNA and RNA
• To discuss the differences and similarities
  between mRNA and tRNA
• To examine the role of the nucleus and nucleolus
  during RNA synthesis
• To study the synthesis of proteins

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• It was Francis Crick and James Watson who
  unraveled the DNA molecule.

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DNA Molecule
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• In 1966 the Genetic code was discovered.
• Scientists are now able to predict
  characteristics by studying DNA. This leads to
  genetic engineering, genetic counseling.

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An international team of scientists began the
project to map the human genome.
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1990Gene therapy was used on patients for the
first time.
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1994The FDA approved the first genetically
engineered food -- FlavrSavr tomatoes engineered
for better flavour and shelf life.
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1997Dolly the Sheep - the first adult animal
clone.
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Dolly the sheep, pictured here with her first
lamb Bonnie
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2000J. Craig Ventor, along with Francis Collins,
jointly announce the sequencing of the entire
human genome.
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The Central Dogma

• DNA codes for the production of DNA (replication)
  and of RNA (transcription).
• RNA codes for the production of protein
  (translation).

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The Central Dogma

• Genetic information is stored in a linear message
  on nucleic acids. We use a shorthand notation to
  write a DNA sequence
• 5'-AGTCAATGCAAGTTCCATGCAT....
• A gene determine the sequence of amino acids in
  proteins. We use a shorthand notation to write a
  protein sequence
• NH2-Met-Gln-Cys-Lys-Phe-Met-His.... (or a one
  letter code M Q C K F M H)

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DNA Structure - Nucleotide
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DNA Structure Double Helix
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Comparison of DNA and RNA
DNA RNA
Found in nucleus Found in nucleus and cytoplasm
Double strands Single strand
Bases A, T, G, C Bases A, U, G, C
Deoxyribose sugar Ribose sugar
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Transcription

• Part of chain B sequence. Uncoiled DNA double
  helix which has split exposing bases

• First stage of protein synthesis
• Occurs in the nucleus
• Double helix uncoils
• Double strands split
• DNA strand acts as template for formation of mRNA
  (messenger RNA)

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Transcription
Single strand of DNA coding for Chain B
Strand of mRNA copied from DNA

• Free RNA nucleotides in the nucleus base pair
  with DNA nucleotides A-T, T-U, G-C, C-G
• Strong bonds form between phosphate group and
  ribose sugar of neighbouring RNA nucleotides
• Catalysed by enzyme RNA polymerase
• mRNA moves out of nucleus through nuclear pore

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Role of Rough Endoplasmic Reticulum

• Network of membranes
• Found in cytoplasm
• Has ribosomes on surface
• Proteins produced during translation pass into ER

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Translation

• Second stage of protein synthesis
• Occurs on ribosomes in cytoplasm
• Code on mRNA is used to make protein chain

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Translation
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Comparison of mRNA and tRNA

• tRNA
• Transfer RNA
• Found in cytoplasm
• Involved in translation
• Assembles amino acids into correct order for
  proteins
• Anti-codons present

• mRNA
• Messenger RNA
• Made in nucleus during transcription
• Moves to cytoplasm
• Codes for protein
• Base triplets - codons

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Overview
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Overview
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Role of Golgi Apparatus

• Found in cytoplasm
• Flattened sacs which are continually formed
• Involved in processing and packaging proteins
• Vesicles bud off with processed protein

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Secretion

• Also called exocytosis
• Vesicle which has pinched off Golgi apparatus
  moves towards cell membrane
• Membrane of vesicle fuses with cell membrane
• Insulin secreted from cell

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The Facts You Need To Know

• page 1-2
• from chromosomes which remain in .
• to the sequence of bases in the DNA