Download Transcription/Translation Notes

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Biology
Transcription and Translation
Objectives:
 To understand how mRNA is made
 To be able to translate an mRNA strand into a protein sequence.
Do Now:
1. What are the 3 types of RNA?
2. What is the purpose of each of them?
3. What are the names of the two processes involved in making proteins?
Notes:
I.
Transcription
a. *only individual genes are transcribed, not an entire strand of DNA.
i. Step 1: DNA molecule unwinds and separates just like in replication.
ii. Step 2: RNA nucleotides match up with their complimentary bases on
the template strand.
1. Practice: Write the complimentary mRNA strand from this
DNA…
ATCGATGGCAAGCTA
iii. Step 3: mRNA detaches once entire gene is done and the DNA
recoils.
1. *Many copies of mRNA can be made from the same gene in a
short period of time.
II.
Translation:
a. Step 1: Translation begins when a ribosome attaches to the beginning end of
an mRNA molecule.
i. *Translation MUST START AT THE LETTERS “AUG”.
ii. * Every 3 letters on the mRNA is called a “Codon” that codes for a
specific amino acid.
b. Step 2: A tRNA molecule carrying an amino acid matches up to a
complementary codon in the mRNA on the ribosome.
i. *tRNA molecules contain “Anticodons” which are 3 bases on the
tRNA.
c. Step 3: The ribosome attaches one amino acid to another as it moves along
the mRNA molecule.
i. Amino acids are attached by peptide bonds.
d. Step 4: The tRNA molecules are released after the amino acids they carry
are attached to the growing chain of amino acids.
e. Step 5: The ribosome completes the translation when it reaches a stop
codon. The newly made protein molecules in the form of a chain of amino
acids, is released.
Practice!
Translate this mRNA sequence. *Remember to start and stop at the right places!!
mRNA:
Peptide Chain:
UCACUAUGCGGACGGACUAATCG