1. A PowerPoint presentation by Gene Tempest
From Gene To Protein
A PowerPoint presentation by Gene Tempest

2. Table of Contents Overview Transcription RNA Processing Translation
Differences in protein Synthesis Between Prokaryotes and Eukaryotes
Point Mutations
Bibliography

3. Overview DNA RNA Protein The one gene-one polypeptide hypothesis
Main processes in protein production in eukaryotes:
1. Transcription
2. RNA processing
3. Translation
The synthesis of RNA under the direction of DNA
Yields the finished mRNA
Actual synthesis of a polypeptide, under the direction of mRNA
DNA
RNA
Protein

4. Animation 17.1

5. Terms
Triplet Code
Template Strand
Codon
Initiation Codon
Termination Codons
Series of three-nucleotide “words” that contain the instructions for making polypeptide chains.
The one out of the two DNA strands that is transcribed.
mRNA base triplet
AUG (also codes for amino acid methionine)
UAA UAG UGA

6. Fig. 17.3

7. Fig. 17.4
Note: Based on mRNA Codon

8. Pries the two strands of DNA apart and hooks together the RNA nucleotides, as they base-pare along the DNA template
Transcription
In eukaryotes, a collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription
A closer look
Stretch of DNA that is transcribed into an RNA molecule
Terms
RNA polymerase
Transcription unit
Promoter
Transcription factors
Terminator
RNA sequence that functions as the actual termination signal
Region of DNA where RNA polymerase attaches and initiates transcription

9. Stages
1. RNA polymerase unwinds the two DNA strands RNA synthesis begins at the starting point on the template strand.
2. The RNA polymerase works its way “downstream”.
5’ ’
3. RNA polymerase transcribes a terminator RNA is released RNA polymerase dissociates from DNA

10. Fig. 17.6

11. Animation 17.2

12. The removal of a large portion of the originally synthesized RNA molecule
RNA Processing
A closer look
Non-coding segments of nucleic acid that lie between coding regions
Terms
Small nuclear ribonucleoproteins; joins with proteins to form the spliceosome
RNA splicing
Introns
Exons
snRNPs
Spliceosome
Cuts at specific points to release the intron, then joins the two exons together
Eventually expressed--or translated into amino acid sequences

13. Stages
1. The ends of each pre-mRNA molecule are modified: the 5’ end is capped off with a modified form of a guanine (G) nucleotide ( 5’ cap )
- a poly(A) tail, consisting of adenine nucleotides, attaches to the 3’ end
2. The spliceosome removes the introns and produces joined exons, now mRNA

14. Animation 17.3

15. Translation Terms Transfer RNA Function:
to transfer amino acids from the cytoplasm to a ribosome
Holds the tRNA carrying the growing polypeptide chain
A closer look
Relaxation of the base-paring rules
Terms
tRNA
Wobble
rRNA
P Site
A Site
E Site
Sites on the large ribosomal subunit
Ribosomal RNA
Function:
structural and catalytic role in ribosomes
Holds the tRNA carrying the next amino acid to be added to the chain
Exit for discarded tRNAs

16. Stages
I. Initiation Small ribosomal subunit binds to a molecule of mRNA A large ribosomal subunit complex completes it
II. Elongation Codon Recognition Peptide bond formation Translocation III. Termination The ribosome accepts a release factor instead of tRNA The release factor hydrolyses the bond between tRNA and P site Ribosomal subunits dissociate

17. Animation 17.4

18. Differences between Prokaryotes and Eukaryotes
Can simultaneously transcribe and translate the same gene
Newly made proteins can diffuse to their sites of function
Nuclear envelope segregates transcription from translation
Have complicated mechanisms for targeting proteins to their appropriate destinations

19. Point Mutations Vocabulary
Chemical changes in just one or a few base pairs in a single gene
Substitutions
Insertions and deletions
Replacement of one nucleotide and its partner in the complementary DNA strand with another pair of nucleotides
Vocabulary
Missense Mutation
Nonsense Mutation
Frameshift Mutation
The altered codon still codes for an amino acid
Addition or loss of one or more nucleotide pairs in a gene
Alterations that change amino acids to a stop signal
Alters the reading frame of the genetic message

20. Bibliography
Campbell, Mitchell, Reece. “Biology Fifth Edition”. Illinois, USA. 1999
Biology Fifth Edition CD-ROM