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BIOL V04 Lecture: From Gene to Protein (CR10-Ch 17)
© copyright 2015 Marta D. de Jesus
I. How does DNA affect phenotype?
A. Archibald Garrod (1909)
B. George Beadle & Edward Tatum (early 1940’s)
C. Overview: information flow & gene expression
II. Transcription
A. Structure
1. nucleotide differences
2. RNA
3. short
B. When does this happen?
C. 3 main kinds of RNA
1. messenger RNAs (mRNA)
2. Other 2 types of RNA - protein-producing machinery
a. transfer RNAs (tRNA)
b. ribosomal RNAs (rRNA)
D. How is it made?
1. Musical analogy
2. similar
a. DNA
b. the information
c. RNA
3. RNA polymerase
a. 3’ end
b. promoter
termination signal
c. transcription unit
d. synthetic process
4. Steps:
a. initiation
1) initiator site
2) upstream
3) RNA polymerase
b. elongation
c. termination & release
d. 1 chromosome can have
E. major differences between prokaryotes & eukaryotes
1. in prokaryotes
2. in eukaryotes
promotor structure in more detail [17.8]
influencing initiation
TATA box
UPE
enhancers
activators
2) transcription factors
c. termination & release of RNA transcript
termination sites
d. post-transcriptional modifications
1) capping
2) tailing
3) removal
(i) involve
- small nuclear RNAs (snRNAs)
small nuclear riboproteins (snRNPs)
- spliceosomes
ribozymes
(ii) alternative splicing
III. Translation
A. foreign language analogy
B. what is it saying?
1. codons
redundancy or degeneracy
Marshall Nirenberg & JH Matthaei
Nobel Prize 1968: Nirenberg, Khorana & Holley
Story about that time: http://nautil.us/issue/21/information/the-thrill-of-defeat
C. How is a protein built?
1. Takes ribosomes
a. made of large & small subunits
b. have 3 sites for tRNAs
c. catalytic activities
(ribosome structure: http://www.rcsb.org/pdb/molecules/pdb10_1.html)
2. Takes tRNAs
a. aminoacyl-tRNA synthetases
b. tRNA structure
anticodon loop
wobble
3. mRNA
4. GTP
D. Steps:
1. initiation
initiation complex
2. chain elongation
a. codon recognition
b. peptide bond formation
c. translocation
d. repeat
3. chain termination
stop codon
release factor
E. polyribosomes/polysomes
F. proteins are folding into their final shape
G. post-translational modifications
1. modified
2. signal sequences of protein
a. proteins for the RER
1) signal peptide/sequence
2) signal-recognition particle (SRP)
3. further editing can also occur: eg: insulin
IV. How accurate do all these processes have to be?
A. mutation
B. point mutation
1. base-pair substitution
a. silent
b. missense
c. nonsense
2. frameshift mutation
a. base-pair insertion
b. base-pair deletion
C. larger DNA changes
1. chromosomal
2. transposon
3. viruses
D. is mutation always bad?
1. bad
2. not so bad
3. good
E. How to test chemicals for mutation-causing ability
1. for mutagens
2. for carcinogens
Helpful resources:
DNA from the Beginning- Molecules of Genetics: http://www.dnaftb.org/15/
The Biology Project: Molecular Biology
http://www.biology.arizona.edu/molecular_bio/molecular_bio.html
NDSU Virtual Cell: Transcription
https://www.youtube.com/watch?v=WsofH466lqk
Biology / Medicine Animations HD: Transcription
https://www.youtube.com/watch?v=pNVPB6NFIZU
NDSU Virtual Cell: Translation
https://www.youtube.com/watch?v=5bLEDd-PSTQ
DNA Learning Center – 3D Animation Library http://www.dnalc.org/resources/3d/