1. Transcription and Translation
Chapter 17

2. Central Dogma DNA mRNA Protein DNA DNA – Replication – nucleus
DNA mRNA – Transcription – Nucleus
mRNA Protein – Translation – Ribosome in the cytoplasm

3. Central Dogma

4. One Gene-One Protein (Polypeptide)
One gene – section of DNA – codes for one protein (polypeptide)
Exceptions – Quaternary level proteins that are made of one or more subunits.
EX: hemoglobin – transports O2 and CO2 in blood
Made from 2 different polypeptides (alpha and beta) therefore two genes code for the proteins that make hemoglobin

5. DNA vs. RNA

6. DNA vs. RNA DNA RNA Nucleus only Double Stranded ATCG
Deoxyribose Sugar
Nucleus and cytoplasm (ribosome)
Single Stranded
AUCG
Ribose sugar
3 types
mRNA - messenger
tRNA - transfer
rRNA - ribosomal

7. Left Page Draw a picture showing the Central Dogma
Something similar to that on slide 1 or 2.
DNA compare contrast – (Double Bubble or T-chart or Venn Diagram)
Summary

8. Transcription DNA  pre-mRNA Copying of DNA’s message to pre-mRNA
Occurs in the nucleus

9. Detailed Transcription
RNA polymerase binds to DNA at promoter region.
Promoter is before the gene that is to be transcribed
Determines which strand of DNA to use
Usually a TATA box in eukaryotes
Initiation – RNA polymerase unwinds DNA and starts RNA synthesis
Aided by transcription factors in eukaryotes
Elongation - adds nucleotides to mRNA strand based on DNA strand in a 5’ 3’ direction.
Termination – RNA polymerase “falls off” the DNA strand when the termination sequence (terminator) is reached.
AAUAAA in eukaryotes

11. Transcription
Flow Map with pictures and summarize

12. RNA Processing Pre-mRNA RNA Occurs in the nucleus
5’ cap – guanine and phosphate cap on the 5’ end of mRNA
3’ poly-A tail – 50 to 250 Adenines are added to the 3’ end of the mRNA
Both the 5’ cap and 3’ poly-A tail facilitate the export of mRNA from the nucleus
Both protect the mRNA from degradation by hydrolytic enzymes in the cytoplasm
Both help ribosomes attach to the 5’ ends of the mRNA strand

13. RNA processing

14. RNA Processing RNA Splicing Keeps the exons  gets rid of the introns
Introns – non-coding sections of mRNA
Don’t leave the nucleus – only on pre-mRNA
Exons – coding sections of mRNA
Leave the nucleus – final mRNA
Keeps the exons  gets rid of the introns
snRNPs – cut the introns
Ribozyme – RNA that functions like an enzyme
Spliceosomes – join remaining exons together to form final mRNA

16. RNA Processing
Bubble Map
Pictures
Summarize

17. Translation mRNA  protein Process of mRNA converting to a protein
Occurs in the cytoplasm – ribosome

18. tRNA Interpreter of mRNA’s message is tRNA – transfer RNA
80 nucleotides long
Hairpin shape – L shaped
One end contains an anticodon which pairs with the codon on the mRNA
Codons on the mRNA determine which amino acid is coded for by the DNA
The other end contains an amino acid attachment site
Aminoacyl-tRNA synthetase attaches the correct amino acid to the tRNA

19. tRNA

20. Ribosomes
Pair codons on mRNA with anticodons on tRNA to form polypeptides
Made of large and small subunits
rRNA – ribosomal RNA
Made in the nucleolus
Contain multiple binding sites
mRNA binding site
P site – peptidyl – tRNA site
A site – aminoacyl – tRNA site
E site – exit site

21. Ribosomes

22. Making a protein Initiation Small subunit binds to mRNA
Start codon AUG – methionine at P site
Elongation
A site recognizes codon and pairs with correct tRNA
Peptide bond forms between the carboxyl end of the polypeptide at the P site and amino acid at the A site
Amino acid in the A site translocates to the P site
Termination
Stop codon is reached at the A site
UAA, UAG, UGA
Release factors free the polypeptide from the ribosome

23. Making a Protein

24. Translation
Diagram
Summarize and explain the process

25. Proteins
Fold spontaneously into primary, secondary, and tertiary structures.
Chaperone proteins assist in folding.
Some polypeptides become quaternary with multiple subunits
Signal peptide – directs proteins through the endomembrane system

26. Prokaryotes vs. Eukaryotes
No nucleus
Transcription and translation same location
Transcription and translation at the same time - coupling
Smaller ribosomes
70 s
Killed by some antibiotics
Nucleus
Pre-mRNA  mRNA
transcription
Larger ribosomes
Translation
80 s

27. Mutations Point Mutations – one base altered Base-pair substitution
Silent mutation – no effect
Missense mutation – changes an amino acid
Nonsense mutation – creates a stop codon
Insertion – extra base
Deletion – removal of a base
Frameshift mutations – nonfunctional proteins

28. Primary
structure
Primary
structure
Exposed
hydrophobic
region
Secondary
and tertiary
structures
Secondary
and tertiary
structures
Quaternary
structure
Normal
hemoglobin
(top view)
Quaternary
structure
Sickle-cell
hemoglobin
Function
Molecules do
not associate
with one
another; each
carries oxygen.
Function
Molecules
interact with
one another and
crystallize into
a fiber; capacity
to carry oxygen
is greatly reduced.
Red blood
cell shape
Normal red blood
cells are full of
individual
hemoglobin
moledules, each
carrying oxygen.
Red blood
cell shape
Fibers of abnormal
hemoglobin deform
red blood cell into
sickle shape.

29. Mutations Bubble Map types of point (non chromosomal) mutations
Summarize and explain how a single point mutation can alter a protein – include levels of protein structure in your explanation.