Protein Synthesis
An intro to
this section!
Transcription
Making RNA from DNA
296-297; 300-303
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Translation
Forming polypeptides
297-300; 304-309
From your reading…
• How many total amino acids are there?
• How many bases (nucleotides) code for each
amino acid?
• A triplet code known as a codon is found on what
strand, DNA or RNA?
• What is a polypeptide chain made up of?
• Is the genetic code universal? (Do all organisms
use the same codon/amino acid genetic code?)
• How does the above question relate to the linked
history of the life on Earth?
From your reading…
• What type of RNA transfers amino acids from the
cytoplasm to the ribosome?
• Where is tRNA made?
• Is tRNA reuseable?
• tRNA is a strand of RNA nucleotides, what is
found at each of its ends?
• Wobble position=Not Needed
• Joining of amino acid to the tRNA is performed by
what type of molecule? (Specific name is not
needed)
From your reading…
•
•
•
•
•
•
Where are the rRNA subunits made?
The order of sites in the ribosome are E, P, A.
P holds:
A holds:
E does what?:
The movement of mRNA and tRNA through the
sites requires energy from whom?
• What type of molecule is the release factor?
• Why are polyribosomes used?
Translation
• Converts/transfers information from mRNA into
amino acids
• Amino acids are the monomers of proteins
• String amino acids together and a protein is made
• 3 RNAs needed
– mRNA (messenger—from nucleus to ribosome)
– rRNA (ribosomal—used in the ribosome)
– tRNA (transfer—transfers the codons into amino acids
using anticodons)
Translation
3 Main Steps
1. Initiation
• mRNA attaches to the ribosome (with the use
of rRNA)
• rRNA reads the mRNA in groups of 3
nucleotides called codons
• Translation starts with a special codon
– AUG—start codon—initiator
Translation
3 Main Steps
2. Elongation
• tRNA carries specific amino acid to the ribosome
• The specific amino acid is determined by the
anticodon of tRNA
• The anticodon pairs with complementary codon
on mRNA (Example: codon AUG; anticodon UAC)
• Peptide bonds form between amino acids, linking
them into proteins
• tRNAs get recycled back to go pick up more
amino acids
Translation
amino acid
tRNA
**Draw this!
anticodon
codon
protein
(linked amino acids)
ribosome
Translation
3 Main Steps
3. Termination
• Protein is released from ribosome when “stop
codon” is reached
– 3 stop codons:
• UAA
• UAG
• UGA
1.
mRNA codon chart
Let’s Try!!
1. If mRNA codon is CCG,
what is the amino acid?
2. If tRNA anticodon is AAC,
what is the mRNA codon?
What is the amino acid?
3. If the DNA template
strand is ATA, what is the
mRNA codon?
What is the amino acid?
2.
3.
Translation Answers
1. Proline
2. UUG ; leucine
3. UAU ; tyrosine
Now….
1. Use codon chart to complete practice worksheet
2. Draw/analyze/explain Figures:
17.9 17.12 17.15 17.16 17.23
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Protein Synthesis
• DNA: TACACCTTCGCGCAATACTGC
• mRNA:
• AA:
AUGUGGAAGCGCGUUAUGACG
START-TRY-LYS-ARG-VAL-MET-THR
• START=METHIONINE