1. Protein Synthesis

2. PROTEIN SYNTHESIS

3. Protein synthesis involves two types of nucleic acids:
DNA (deoxyribonucleic acid)
RNA (ribonucleic acid)

4. Differences Between DNA and RNA
DNA RNA
double-stranded single-stranded
sugar = deoxyribose sugar = ribose
bases = A,T,C,G bases = A,U,C,G
(uracil takes the place of thymine)

5. RNA
RNA, like DNA, is a polymer formed by a sequence of nucleotides

7. Free Nucleotide

8. Protein Synthesis involves two processes:
Transcription: the copying of the genetic instructions (DNA) into a molecule of mRNA
Translation: mRNA is used to assemble an amino acid sequence into a polypeptide (protein)

9. Pathway to Making a Protein
DNA
mRNA
Protein
Transcription
Translation

10. Transcription
Process in which genetic instructions are transcribed (rewritten) to form an RNA molecule.
occurs in the nucleus of eukaryotic cells
Transcription occurs in 3 major steps:

11. RNA polymerase (enzyme) binds to the promoter.
Step 1:
RNA polymerase (enzyme) binds to the promoter.
Promoter – a specific nucleotide sequence of DNA that initiates transcription. (“START” sequence)
DNA strand unwinds and separates

12. Step 2:
RNA polymerase adds free RNA nucleotides that are complementary to the nucleotides on one of the DNA strands.

13. Complementary Pairings:
EXAMPLE:
DNA RNA
A = U
T = A
C = G
G = C

14. Step 3:
RNA polymerase reaches the “termination signal” sequence of nucleotides that marks the end of transcription.
RNA polymerase releases both the DNA strand and the newly formed RNA strand.

15. The RNA made during transcription can be any of the three types of RNA:
messenger RNA (mRNA)
transfer RNA (tRNA)
ribosomal RNA (rRNA)

16. Transcription Animation

17. Translation (Protein Synthesis)
RNA  protein

18. Translation occurs in the cytoplasm of the cell, at the ribosome
All RNAs needed in translation
mRNA, tRNA, and rRNA

19. Messenger RNA (mRNA)
Carries coded instructions for protein synthesis (translation)
From the DNA in the nucleus to the ribosome

20. The genetic code Codons instructions for making a
protein, a series of three nucleotides
on the mRNA
Each codon signifies
start, stop, or an amino acid

21. The genetic code

22. Transfer RNA (tRNA)
Brings amino acids to the ribosome so it can build proteins
It has Anticodons
3 nucleotide sequence
complementary to the mRNA
codon

23. Ribosomal RNA (rRNA)
Makes up ribosomes

24. Translation Step 1:
mRNA from nucleus Through cytoplasm to the ribosome
mRNA start codon AUG signals beginning of protein

25. Translation Step 2:
tRNA with the complementary anticodon carries amino acid (a.a.) to bind to the codon

26. Translation Step 3:
Enzymes help form peptide bonds between amino acids
Peptide bond

27. Translation Step 4: This continues until a stop codon is reached
Protein is released into the cell

28. Translation Animation