RNA Structure

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RNA Structure

• Like DNA, RNA is a nucleic acid.
• RNA is a nucleic acid made up of repeating
  nucleotides

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RNA differs from DNAin three different ways.

• The sugar in RNA is ribose
• RNA is single- stranded
• RNA contains the base uracil instead of thymine.
• Like thymine, uracil can form bonds with adenine

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• A molecule called RNA ribonucleic acid is used
  to decode the instructions in DNA,

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Transcription

• The instructions for making a protein are
  transferred from a gene (DNA) to RNA
• Transcription DNA ? RNA

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• Segment of DNA unwinds and unzips
• RNA is produced one nucleotide at a time by
  matching base pairs with the nucleotides in DNA.

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• After the synthesis is complete, the RNA
  separates from the DNA and the DNA recoils into
  its helix.
• The RNA (mRNA) strand leaves the nucleus and goes
  into cytoplasm

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Forms of RNA
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Messenger RNA - mRNA

• mRNA carries the information to the cytoplasm
  where the ribosomes can make it into protein.
• "Blueprint" for protein synthesis that is
  transcribed from one strand of the DNA (gene) and
  which is translated at the ribosome into a
  polypeptide sequence.

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Ribosomal rRNA

• a structural component of the ribosome.

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• tRNA
• molecule that converts nucleic acid sequence to
  protein sequence

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• tRNA - transfer RNA
• carries the amino acid elements of a protein to
  the appropriate place as coded for by the mRNA.
• Small, single-stranded RNA molecules that bind to
  amino acids and deliver them to the proper codon
  on messenger RNA.

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• Ribosomes take RNA coded information and
  "translate" that information into chains of amino
  acids called pollypeptides
• A protein is made up of one or more polypeptide
  chains.

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• Messenger RNA (mRNA) is the blueprint for
  construction of a protein.
• Ribosomal RNA (rRNA) is the construction site
  where the protein is made.
• Transfer RNA (tRNA) is the truck delivering the
  proper amino acid to the site at the right time.

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Translation

• The ribosome reads the mRNA sequence and
  translates it (or decodes it) into an amino acid
  sequence in a polypeptide.

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• Polypeptides are chains of amino acids.
• Proteins are made up of one or more polypeptide
  molecules.
• So.the building block of proteins are
  ___________________.

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• There are 20 essential amino acids that make up
  proteins.
• The instructions in DNA specify the order in
  which the amino acids are put together.

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• RNA contains 4 different nucleotides.
• (Language 4 letters)
• How can a code with only 4 letters carry
  instructions for 20 amino acids?

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• of letters of words
• 1 4
• 2 16
• 3 64
• The genetic code could signify 64 different words

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• The group of 3 nucleotides in mRNA that specifies
  an amino acid is known as a codon.
• Think of codons as the words of the genetic
  message.

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• Example The following sequence of nucleotides
  in mRNA
• AAACACGGU
• Would be read as 3 codons
• AAA- CAC-GGU
• And each codon represents a different _____.

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• Page figure
• Shows all 64 possible codons of the genetic
  code.
• Notice More than one codon can specify the same
  amino acid.

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How do tRNAs recognize to which codon to bring an
amino acid? The tRNA has an anticodon that is
complementary to the codon on the mRNA. Each tRNA
only binds the appropriate amino acid for its
anticodon
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• amino acids are carried by the molecules of tRNA.
  
• The ribosomes read the codons in mRNA allowing
  tRNA molecules to bring the proper amino acid.
  (the anti-codon on tRNA bonds to the proper codon
  on mRNA)