Protein Synthesis Step 2: Translation
Dec 28, 2015
Protein SynthesisStep 2: Translation
ReviewProtein Synthesis: The process by
which the message of DNA is used to make proteins
Step 1: Transcription◦Takes place in the nucleus◦Changes DNA to mRNA◦Base Pairs: A-U and C-G
Step Two: Translation “to decode ordecipher the meaning of” Now that our mRNA
molecule has been made, it’s time for its message to be made into a protein sequence.
How does the mRNA sequence translate into an amino acid sequence?
Step Two: TranslationProblem:
◦There are 20 different amino acids.
◦There are 4 RNA bases.phe ile val pro ala his asn asp cys arg
leu met ser thr tyr gln lys glu trp gly
AT
CG
Step 2: TranslationTranslation in 3 steps:
1. mRNA leaves the nucleus and finds a ribosome in the cytoplasm
2. tRNA brings amino acids to the ribosome
3. rRNA joins the amino acids together by matching the codes between mRNA and tRNA
Ribosome
(rRNA)
tRNA
Step Two: TranslationWatch this simplified animation:http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/translation.swf
Watch the more complex animation!
http://www-class.unl.edu/biochem/gp2/m_biology/animation/gene/gene_a3.html
Step Two: Translation1. So how do you exactly go about
determining what protein your cells are going to make?
2. FIRST, divide the mRNA sequence into codons.
◦ Codons are three-base sections of mRNA:
AUG|CGU|ACU|GAU|CGU|UCA|GAU|UGA
Step Two: Translation
2. Since each 3-letter combination “codes” for an amino acid, you need to figure out what amino acid matches up with each codon:
?
AUG|CGU|ACU|GAU|CGU|UCA|GAU|UGA
Use a Codon Chart!
Step Two: Translation
2. Since each 3-letter combination “codes” for an amino acid, you need to figure out what amino acid matches up with each codon:
met
AUG|CGU|ACU|GAU|CGU|UCA|GAU|UGA
?
Step Two: Translation
2. Since each 3-letter combination “codes” for an amino acid, you need to figure out what amino acid matches up with each codon:
met
AUG|CGU|ACU|GAU|CGU|UCA|GAU|UGA
Important Codons/Amino Acids!
Codon Amino Acid
Signal
AUG Methionine
START
UAA None STOP
UAG None STOP
UGA None STOP
Ribosome
(rRNA)
tRNA
How does tRNA know where to go?
tRNA has an anticodon that coordinates with the codon on
mRNA
Anti-codon
Anti-codon and
codon pair up!
RECAP:
1. DNA is transcribed into mRNA in the nucleus.
2. The mRNA leaves the nucleus and enters the cytoplasm.
3. The protein is translated from the mRNA sequence using tRNA and amino acids.