1 Division Ave. High School Ms. Foglia AP Biology 2007-2008 AP Biology From Gene to Protein How Genes Work AP Biology Organelles nucleus ribosomes endoplasmic reticulum (ER) Golgi apparatus vesicles Making proteins small ribosomal subunit large ribosomal subunit cytoplasm mRNA nuclear pore AP Biology Nucleus & Nucleolus AP Biology Nucleolus Function ribosome production build ribosome subunits from rRNA & proteins exit through nuclear pores to cytoplasm & combine to form functional ribosomes small subunit large subunit ribosome rRNA & proteins nucleolus AP Biology small subunit large subunit Ribosomes Function protein production Structure rRNA & protein 2 subunits combine 0.08μm Ribosomes Rough ER Smooth ER AP Biology membrane proteins Types of Ribosomes Free ribosomes suspended in cytosol synthesize proteins that function in cytosol Bound ribosomes attached to endoplasmic reticulum synthesize proteins for export or for membranes PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com
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Division Ave. High School Ms. FogliaAP Biology
AP Biology
Ribosomes
Met
5'
3'
UUA C
A G
APE
� A site (aminoacyl-tRNA site)� holds tRNA carrying next amino acid to
be added to chain
� P site (peptidyl-tRNA site)� holds tRNA carrying growing
polypeptide chain
� E site (exit site)� empty tRNA
leaves ribosome from exit site
AP Biology
Building a polypeptide� Initiation
� brings together mRNA, ribosome subunits, initiator tRNA
� Elongation� adding amino acids based on
codon sequence
� Termination� end codon 123
Leu
Leu Leu Leu
tRNA
Met MetMet Met
PE AmRNA5' 5' 5' 5'
3' 3' 3' 3'U UA AAAC
CC
AU UG GGU
UA AA
ACC
CAU UG G
GUU
A AAAC
CC
AU UG GGU U
A AACCA U UG G
G A C
ValSer
AlaTrp
releasefactor
AA A
CCU UGG 3'
AP Biology
Protein targeting � Signal peptide
� address label
Destinations:� secretion� nucleus� mitochondria� chloroplasts� cell membrane� cytoplasm� etc…start of a secretory pathway
AP Biology
Can you tell the story?
DNA
pre-mRNA
ribosome
tRNA
aminoacids
polypeptide
mature mRNA
5' cap
polyA tail
large ribosomal subunit
small ribosomal subunit
aminoacyl tRNAsynthetase
E P A
5'
3'
RNA polymerase
exon introntRNA
2007-2008AP Biology
Got Questions?Can I translate that for you?
2007-2008AP Biology
Substitute Slidesfor Student Print version
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Division Ave. High School Ms. FogliaAP Biology
AP Biology
Can you tell the story?
2007-2008AP Biology
Extra Slides(used some years & not others)
AP Biology
Translation � Codons
� blocks of 3 nucleotides decoded into the sequence of amino acids
AP Biology
Building Proteins� Organelles involved
� nucleus� ribosomes� endoplasmic reticulum
(ER)� Golgi apparatus� vesicles
nucleus ribosome ERGolgi
apparatusvesicles
The Protein Assembly Line
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 DNA in nucleus to cytoplasm?� messenger RNA
nucleus AP Biology
Alternative splicing� Alternative mRNAs produced from same gene
� when is an intron not an intron…� different segments treated as exons
Starting to gethard to
define a gene!
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Division Ave. High School Ms. FogliaAP Biology
AP Biology
Domains
� Modular architectureof many proteins� exons may represent
functional units of protein
� easier to mix and match in the production of new proteins?
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 polypepti des� but each polypeptide has its own gene
� One gene – one polypeptide?� but many genes only code for RNA (tRNA, rRNA…)
� One gene – one product?� but many genes code for
more than one product …So…
Where doesthat leave
us?!
AP Biology
Defining a gene…““““Defining a gene is problematic becauseDefining a gene is problematic becauseDefining a gene is problematic becauseDefining a gene is problematic because…………one gene can code for several protein products, one gene can code for several protein products, one gene can code for several protein products, one gene can code for several protein products, some genes code only for RNA, two genes can some genes code only for RNA, two genes can some genes code only for RNA, two genes can some genes code only for RNA, two genes can overlap, and there are many other complications.overlap, and there are many other complications.overlap, and there are many other complications.overlap, and there are many other complications.””””