RNA

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RNA

• Chapter 12-3

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The Genetic Code

• DNA is a code that stores hereditary information
• For it to be used by the cell, it must be decoded
  
• The first step in decoding this information is to
  copy the information from DNA into RNA

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What is RNA?

• RNA is moleculde composed of a single strand of
  nucleotides
• RNA contains the nucleotides adenine, guanine,
  cytosine and uracil
• The five-carbon sugar that makes up the
  nucleotides in RNA is ribose

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Three Types of RNA

• Messenger RNA (mRNA)- serves as a template for
  the assembly of amino acids when proteins are
  made
• Transfer RNA (tRNA)- folded back strand and can
  exist in 20 or more varieties, each bonded to one
  specific amino acid
• Ribosomal RNA (rRNA)- glob-shaped form found on
  the ribosomes. It assembles the amino acids in
  the correct order

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Transcription

• To write across
• Process by which mRNA is produced from DNA
• Enzyme called RNA polymerase unzips DNA

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Transcription

• After the DNA molecule is separated, RNA
  polymerase uses the one-sided DNA as a template
• Complimentary base pairs of form along the DNA
  template
• C-G
• A-U

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The Genetic Code

• After DNA has been transcribed into RNA, it is
  time for it to be decoded further
• The next step is to decode mRNA into amino acid
  chains
• This process is called translation

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Codons

• A group of three sequential mRNA bases is called
  a codon
• Each codon is specific for an amino acid
• There are 64 codons that code for amino acids
  (Figure 12-17)

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(No Transcript)
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Translation

• Translation takes place in the ribosome
• During translation, the cell uses information
  from mRNA to assemble proteins
• Translation binds tRNA to mRNA using the rule of
  base pairing

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tRNA

• Transfer RNA (tRNA) consists of three base pairs
  called an anticodon attached to a specific amino
  acid

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Translation

• mRNA attaches to the ribosome
• As mRNA moves through the ribosome, tRNA
  anticodon attaches to mRNA codon
• Each tRNA molecule carries an amino acid
• As mRNA continues to move through the ribosome, a
  chain of amino acids forms
• A long chain of amino acids will code for a
  specific protein

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Translation
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Translation