1. Translation

2. Translation
The final product of gene expression is a polypeptide chain of amino acids whose sequence was prescribed by the genetic code.

3. The Players mRNA transcribed from genomic DNA
Transfer RNA (tRNA) to transport amino acids
Ribosome to “read” mRNA, align amino acids attached to tRNA and create the peptide bonds between adjacent amino acids

4. Ribosome Two subunits composed of protein and ribosomal RNA (rRNA)
The rRNA is a structural component of the ribosome subunits

5. The Ribosome (Eukaryote)
18S RNA +
33 proteins
80S
60S
28S RNA +
49 proteins

6. tRNA
tRNAs are small, extremely stable RNA structures shaped like a cloverleaf due to internal base pairing
They are almost identical in both prokaryotes and eukaryotes
They contain a number of posttranscriptional modifications, including non-traditional bases (other than (A, U, G and C)

7. tRNA

8. tRNA The amino acid attaches to the 3’ end of the tRNA
tRNA can base pair with the codon in mRNA at the anticodon on the tRNA

9. Charging tRNA with an Amino Acid
An individual tRNA is specific for a single amino acid. (There are at least 20 different tRNAs)
Charging is the process of covalently attaching an amino acid to the tRNA
Charging is accomplished by aminoacyl tRNA synthetases, each of which is specific for an amino acid.

10. Prokaryotes vs. Eukaryotes
The process is essentially the same, but somewhat more complicated in eukaryotes.
What I am showing you is the process for prokaryotes, but at the end I’ll talk a little bit about eukaryotes.

11. Steps in Translation
Initiation—the two subunits of the ribosome come together and the start codon on the mRNA in the ribosome is aligned to set the reading frame
Elongation—Charged tRNAs attach and peptide bonds form between the amino acids
Termination

18. Prokaryotes vs. Eukaryotes

19. Prokaryotes vs. Eukaryotes
Translation takes place directly after transcription
mRNA is not modified
Transcription and translation take place in the same area

21. 3’ 5’

22. Prokaryotes vs. Eukaryotes
Transcript is modified before leaving the nucleus (5’ cap and 3’ poly-A tail)
Modifications increase translation efficiency and lifespan of the mRNA
Translation takes place on ribosomes located in the rough endoplasmic reticulum (translation is physically separated from transcription)

23. Eukaryotes

24. Prokaryotes vs. Eukaryotes
Influence on gene expression forms the basis of function in many antibiotics.
The purpose is to impair function in the prokaryote without disrupting function in eukaryotes.

25. Antibiotics
Tetracycline: Blocks attachment of the AA-tRNA to the A site in the ribosome
Erythromycin: Blocks the movement of the ribosome down the mRNA
Streptomycin: Blocks formation of the initiation complex and causes miscoding
Rifamycin: Blocks transcription by blocking binding of RNA polymerase