Download - Chapter 14
![Page 1: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/1.jpg)
Biology 114AP Biology
Chapter 14.
From Gene to Protein
![Page 2: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/2.jpg)
AP Biology
Metabolism teaches us about genes Metabolic defects
studying metabolic diseases suggested that genes specified proteins
alkaptonuria (black urine from alkapton) PKU (phenylketonuria)
each disease is caused by non-functional enzyme
A B C D E
Genescreate
phenotype
![Page 3: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/3.jpg)
AP Biology
![Page 4: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/4.jpg)
AP Biology
1 gene – 1 enzyme hypothesis Beadle & Tatum
Compared mutants of bread mold, Neurospora fungus
created mutations by X-ray treatments X-rays break DNA inactivate a gene
wild type grows on “minimal” media sugars + required precursor nutrient to synthesize
essential amino acids mutants require added amino acids
each type of mutant lacks a certain enzyme needed to produce a certain amino acid
non-functional enzyme = broken gene
![Page 5: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/5.jpg)
AP Biology
Beadle & Tatum 1941 | 1958
George Beadle
Edward Tatum
![Page 6: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/6.jpg)
AP Biology
Beadle & Tatum’s Neurospora experiment
![Page 7: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/7.jpg)
AP Biology
So… What is a gene? One gene – one enzyme
but not all proteins are enzymes but all proteins are coded by genes
One gene – one protein but many proteins are composed of several
polypeptides but each polypeptide has its own gene
One gene – one polypeptide but many genes only code for RNA
One gene – one product but many genes code for
more than one product …
Where doesthat leave
us?!
![Page 8: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/8.jpg)
AP Biology
Defining a gene…“Defining a gene is problematic because… one gene can code for several protein products, some genes code only for RNA, two genes can overlap, and there are many other complications.”
– Elizabeth Pennisi, Science 2003
gene
polypeptide 1
polypeptide 2
polypeptide 3
RNAgeneIt’s hard to
hunt for wabbits,if you don’t knowwhat a wabbitlooks like.
![Page 9: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/9.jpg)
AP Biology
proteinRNA
The “Central Dogma”
DNAtranscription translation
replication
How do we move information from DNA to proteins?
For simplicity sake,let’s go back togenes that codefor proteins…
![Page 10: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/10.jpg)
AP Biology
From nucleus to cytoplasm… Where are the genes?
genes are on chromosomes in nucleus Where are proteins synthesized?
proteins made in cytoplasm by ribosomes How does the information get from
nucleus to cytoplasm? messenger RNA
nucleus
![Page 11: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/11.jpg)
AP Biology
RNA ribose sugar N-bases
uracil instead of thymine U : A C : G
single stranded mRNA, rRNA, tRNA,
siRNA….
RNADNAtranscription
![Page 12: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/12.jpg)
AP Biology
Transcription Transcribed DNA strand = template strand
untranscribed DNA strand = coding strand Synthesis of complementary RNA strand
transcription bubble Enzyme
RNA polymerase
![Page 13: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/13.jpg)
AP Biology
Role of promoter1. Where to start reading
= starting point
2. Which strand to read
= template strand
3. Direction on DNA
= always reads DNA 3'5'
Transcription in Prokaryotes Initiation
RNA polymerase binds to promoter sequence on DNA
![Page 14: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/14.jpg)
AP Biology
Transcription in Prokaryotes Promoter sequences
RNA polymerase molecules bound to bacterial DNA
![Page 15: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/15.jpg)
AP Biology
Transcription in Prokaryotes Elongation
RNA polymerase unwinds DNA ~20 base pairs at a time
reads DNA 3’5’ builds RNA 5’3’ (the energy governs the synthesis!)
No proofreading 1 error/105 bases many copies short life not worth it!
![Page 16: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/16.jpg)
AP Biology
Transcription
RNA
![Page 17: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/17.jpg)
AP Biology
Transcription in Prokaryotes Termination
RNA polymerase stops at termination sequence
mRNA leaves nucleus through pores
RNA GC hairpin turn
![Page 18: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/18.jpg)
Biology 114AP Biology
Transcription in Eukaryotes
![Page 19: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/19.jpg)
AP Biology
Prokaryote vs. Eukaryote genes Prokaryotes
DNA in cytoplasm
circular chromosome
naked DNA
no introns
Eukaryotes DNA in nucleus linear
chromosomes DNA wound on
histone proteins introns vs.
exons
eukaryoticDNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
Exon: Segmnent of DNA that is both transcribed into RNA and translated into protein
Intron: Portion of mRNA as transcribed from Eukaryotic DNA that is removed by enzymes before mRNA is translated into proteins
![Page 20: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/20.jpg)
AP Biology
Transcription in Eukaryotes 3 RNA polymerase enzymes
RNA polymerase I only transcribes rRNA genes
RNA polymerase I I transcribes genes into mRNA
RNA polymerase I I I only transcribes tRNA genes
each has a specific promoter sequence it recognizes
![Page 21: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/21.jpg)
AP Biology
Transcription in Eukaryotes Initiation complex
transcription factors prokarytoes have 1 the holoenzyme, bind to promoter region upstream of gene
proteins which bind to DNA & turn on or off transcription
TATA box binding site like a prokaryote, too simple, additional control for time and tissue specific.
only then does RNA polymerase bind to DNA
![Page 22: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/22.jpg)
AP Biology
A A A A A3' poly-A tail
CH3
mRNA
5'
5' cap
3'
G PPP
Post-transcriptional processing Primary difference between Pro&Euk Primary transcript
eukaryotic mRNA needs work after transcription Protect mRNA
from RNase enzymes in cytoplasm add 5' cap add polyA tail
Edit out introns
eukaryoticDNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
primary mRNAtranscript
mature mRNAtranscript
pre-mRNA
spliced mRNA
50-250 A’s
![Page 23: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/23.jpg)
AP Biology
5’ CAP 3’ Poly Tail “PROTECTION” Eukaryotes ; The first base in transcript is
usually A or G and modified by GTP to the 5’ PO4 group forming a 5’ Cap. The G nucleotide in the cap is joined to the transcript by its 5’ end making the only 5’ to 5’ bond. This protects the mRNA cap from degradation.
The Euk transcript is cleaved downstream from (AAUAAA) A series of residues called the 3’ poly a tail are added by poly-A-polymerase. Adds protection.
![Page 24: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/24.jpg)
AP Biology
Transcription to translation Differences between
prokaryotes & eukaryotes time & physical separation
between processes RNA processing
![Page 25: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/25.jpg)
AP Biology
Translation in Prokaryotes Transcription & translation are
simultaneous in bacteria DNA is in
cytoplasm no mRNA
editing needed
![Page 26: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/26.jpg)
AP Biology
mRNA
From gene to protein
DNAtranscription
nucleus cytoplasm
mRNA leaves nucleus through nuclear pores
proteins synthesized by ribosomes using instructions on mRNA
aa
aa
aa
aa
aa
aa
aa
aa
ribosome
proteintranslation
![Page 27: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/27.jpg)
AP Biology
Removing Introns Intron: Non-coding sequence 24% out
of human genome Exon: expressed 1% encode for
proteins Pre-mRNA splicing in the nucleus
snRNP cluster to make splicesosome which recognize and cut out introns.
![Page 28: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/28.jpg)
AP Biology
How does mRNA code for proteins?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Met Arg Val Asn Ala Cys Alaprotein
?
How can you code for 20 amino acids with only 4 nucleotide bases (A,U,G,C)?
![Page 29: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/29.jpg)
AP Biology
Cracking the code Nirenberg & Matthaei
determined 1st codon–amino acid match UUU coded for phenylalanine
created artificial poly(U) mRNA added mRNA to test tube of
ribosomes, tRNA & amino acids mRNA synthesized single
amino acid polypeptide chain
1960 | 1968
phe–phe–phe–phe–phe–phe
![Page 30: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/30.jpg)
AP Biology Marshall NirenbergHeinrich Matthaei
![Page 31: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/31.jpg)
AP Biology
Translation Codons
blocks of 3 nucleotides decoded into the sequence of amino acids
![Page 32: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/32.jpg)
AP Biology
AUGCGUGUAAAUGCAUGCGCCmRNA
mRNA codes for proteins in triplets
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Met Arg Val Asn Ala Cys Alaprotein
?
![Page 33: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/33.jpg)
AP Biology
The code For ALL life!
strongest support for a common origin for all life
Code is redundant several codons for
each amino acid
Why is this a good thing?
Start codon AUG methionine
Stop codons UGA, UAA, UAG
![Page 34: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/34.jpg)
AP Biology
How are the codons matched to amino acids?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
aminoacid
tRNA
anti-codon
codon
5' 3'
3' 5'
3' 5'
UAC
MetGCA
ArgCAU
Val
![Page 35: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/35.jpg)
AP Biology
proteinaa
aa
aa
aa
aa
aa
aa
aaaa
aa
aa
transcription
cytoplasm
nucleus
translation
![Page 36: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/36.jpg)
AP Biology
tRNA structure “Clover leaf” structure
anticodon on “clover leaf” end amino acid attached on 3' end
![Page 37: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/37.jpg)
AP Biology
Loading tRNA
Aminoacyl tRNA synthetase enzyme which bonds
amino acid to tRNA endergonic reaction
ATP AMP energy stored in
tRNA-amino acid bond unstable so it can release amino acid
at ribosome
![Page 38: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/38.jpg)
AP Biology
Ribosomes Facilitate coupling of
tRNA anticodon to mRNA codon organelle or enzyme?
Structure ribosomal RNA (rRNA)
& proteins 2 subunits
large small
![Page 39: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/39.jpg)
AP Biology
Ribosomes P site (peptidyl-tRNA site)
holds tRNA carrying growing polypeptide chain
A site (aminoacyl-tRNA site) holds tRNA carrying next amino acid to
be added to chain E site (exit site)
empty tRNA leaves ribosome from exit site
![Page 40: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/40.jpg)
AP Biology
Building a polypeptide Initiation
brings together mRNA, ribosome subunits, proteins & initiator tRNA
Elongation Termination
![Page 41: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/41.jpg)
AP Biology
Elongation: growing a polypeptide
![Page 42: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/42.jpg)
AP Biology
Termination: release polypeptide Release factor
“release protein” bonds to A site bonds water molecule to polypeptide chain
Now what happens to the polypeptide?
![Page 43: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/43.jpg)
AP Biology
Protein targeting Signal peptide
address label
Destinations: secretion nucleus mitochondria chloroplasts cell membrane cytoplasm
start of a secretory pathway
![Page 44: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/44.jpg)
AP Biology
Can you tell the story?
DNA
pre-mRNA
ribosome
tRNA
aminoacids
polypeptide
mature mRNA
5' cap
polyA tail
large subunit
small subunit
aminoacyl tRNAsynthetase
E P A
5'
3'
RNA polymerase
exon intron
tRNA
![Page 45: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/45.jpg)
AP Biology
Put it all together…
![Page 46: Chapter 14](https://reader035.vdocuments.us/reader035/viewer/2022062422/56813a9a550346895da293e6/html5/thumbnails/46.jpg)
Biology 114AP Biology
Any Questions??