NOTES: 11'2 RNA

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NOTES 11.2 RNA Protein Synthesis

• Vocabulary
• Messenger RNA (mRNA)
• Ribosomal RNA (rRNA)
• Transfer RNA (tRNA)
• Transcription
• RNA Polymerase
• Codon
• Translation
• Anticodon

• Key Concepts
• What are the 3 main types of RNA?What is
  transcription?
• What is translation?

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Genes and Proteins

• RECALL the sequences of nucleotides in DNA
  contain INFORMATION!
• This information is put to work through the
  production of PROTEINS.

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What do proteins do for the body?

• Proteins are diverse
• ? control chemical messages in cell
• ? direct the synthesis of carbos, lipids, and
  nucleotides
• ? enzymes
• ? give the cell structure and
• movement
• Goal of protein synthesis
• MAKE A PROTEIN

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Protein Structure

• RECALL proteins are polymers of AMINO ACIDS
• The sequence of nucleotides in each GENE contains
  the information for the sequence of AMINO ACIDS
  in a single protein
• Each human cell contains
• about 20-30,000 genes

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RNA

• Like DNA made of nucleotides
• copy of DNA segment
• 3 main types mRNA, rRNA, tRNA
• 3 differences
• 1) sugar ribose
• 2) single stranded
• 3) instead of the base thymine (T), RNA uses
  URACIL (U)

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Job of RNA Function in Protein Synthesis
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Role of RNA an analogy

• Imagine what goes into a new car being built on
  an automobile assembly line
• Engineers make the design and tell the workers
  how to make the cars
• Workers follow the directions to build the cars
• Suppliers bring parts to the assembly line so
  they can be installed in the car

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Role of RNA an analogy

• Now imagine what goes into PROTEIN SYNTHESIS
• DNA provides the workers with the instructions
  for making proteins
• The workers (RNA molecules!) follow the
  instructions from DNA and build the proteins
• Other workers (other RNA molecules) bring parts
  (AMINO ACIDS) over to the assembly line

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3 Types of RNA

• Messenger RNA (mRNA) brings information from the
  DNA in the nucleus out to the ribosomes
• Ribosomal RNA (rRNA) clamp on to the mRNA and
  use its information to assemble amino acids into
  a protein
• Transfer RNA (tRNA) the supplier transports
  amino acids to the ribosome

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DNA ? RNA

• How does the information in DNA , which is found
  in the nucleus, get out to the ribosomes in the
  cytoplasmit needs a MESSENGER!

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Transcription

• Step 1 (of 2) of protein synthesis
• Transcribe to make a copy
• transcribing DNA information (gene instructions)
  into mRNA
• mRNA can leave the nucleus ? ribosomes in the
  cytoplasm
• special base sequences in DNA are recognized by
  RNA as start and stop signals
• Start sequence called PROMOTER region of DNA

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Details of the Process

• 1. RNA polymerase attaches to DNA at the site
  where instructions for the needed protein begins
  it separates the 2 DNA strands

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• 2. RNA polymerase synthesizes the mRNA strand
  using complementary base-pairing

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• Rememberthere arent T bases in RNA
• C binds with G
• DNA A binds with RNA U

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A
B
Which strand was copied? A or B
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• 3. when RNA polymerase reaches the end or "STOP"
  part of the genetic code for that protein, it
  releases
• 4. DNA re-zips
•  5. finished mRNA (message) leaves the nucleus
  and goes to a ribosome in the cytoplasm

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• Bases are grouped by 3
• Called a CODON (code)

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Transcription
Translation
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• Transcription ends with mRNA which will exit the
  nucleus to the cytoplasm
• So if transcription is the first step of Protein
  Synthesis, what happens next in the cytoplasm?

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TRANSLATION

• Making a protein (string of amino acids)
  translating from the language of nucleic acids
  into a polypeptide
• How does it go from mRNA (copy of DNA) to amino
  acids (building blocks of proteins)?
• ? A group of 3 mRNA bases makes up a codon
  (think of as a code word)
• ? each codon specifies a particular amino acid
• ? there are start and stop codons

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The Mechanism...

• 1) mRNA attaches onto the ribosome
• ? 3 nucleotides of mRNA codon
• 2nd kind of RNA ribosomal RNA (rRNA)
• ? makes up the majority of the ribosome

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The Mechanism continued...

• 3rd kind of RNA transfer RNA (tRNA)
• ? carries amino acids to the ribosomes (amino
  acids join together)
• ? 3 nucleotides of tRNA that match or
  compliment the mRNA anticodon
• ? there are 64 different tRNA molecules
  (more than 1 for each amino acid)
• ? REDUNDANCY of the CODE!!

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tRNA
Amino acid
tRNA anticodon
mRNA codon
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amino acid
tRNA
anticodon
codon (mRNA)
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The Mechanism continued...

• 2) By matching the codon of mRNA to the anticodon
  of tRNA, the correct amino acid is put into place

Next tRNA goes here!!!!
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The Mechanism continued...

• 3) a peptide bond is formed between the 2 amino
  acids

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The Mechanism continued...

• 4) protein chain continues to grow until a stop
  codon is reached on the mRNA
• ? no tRNA exists for stop codons

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Amino acid

•   Molecules of tRNA are specific for only 1
  amino acid
• -one end of tRNA attaches to a specific amino
  acid
• -the other end attaches to mRNA codon by base
  pairing
• (anticodon a sequence of 3 bases on tRNA)

tRNA anticodon
mRNA codon
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• ? tRNAs decode the genetic message codon by codon

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• table 11.2 on
• page 298 shows
• the dictionary
• for the codons
• and their
• corresponding
• amino acids

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Transcription
Translation
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Translation All At Once
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PROTEIN SYNTHESIS All At Once
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PROTEIN SYNTHESIS
DNA
Step 1. TRANSCIPTION (nucleus)
mRNA
Step 2. TRANSLATION (ribosome)
tRNA
PROTEIN
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Protein Synthesis
the whole
process
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Protein Synthesisvideo
http//www.sciencenetlinks.com/interactives/protei
n.html
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PRACTICE

• DNA T A C C G C G G T T T A A C T
• RNA
• amino
• acids

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PRACTICE

• DNA T A C C G C G G T T T A A C T
• RNA A U G G C G C C A A A U U G A
• amino
• acids

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PRACTICE

• DNA T A C C G C G G T T T A A C T
• RNA A U G G C G C C A A A U U G A
• amino
• acids met ala - pro - asn - STOP