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From Gene to Protein. How Genes Work. What do genes code for?. How does DNA code for cells & bodies? how are cells and bodies made from the instructions in DNA. DNA. proteins. cells. bodies. The “Central Dogma”. Flow of genetic information in a cell - PowerPoint PPT Presentation
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AP Biology
What do genes code for?
proteins cells bodies
How does DNA code for cells & bodies? how are cells and bodies made from the
instructions in DNA
DNA
AP Biology
The “Central Dogma” Flow of genetic information in a cell
How do we move information from DNA to proteins?
proteinRNADNA trait
AP Biology
Beadle & Tatum 1941 | 1958
George Beadle
Edward Tatum
"for their discovery that genes act by regulating definite chemical events"
one gene : one enzyme hypothesis
AP Biology
mRNA
From gene to protein
DNA
nucleus cytoplasm
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
protein
trait
AP Biology
RNA ribose sugar N-bases
____________________ ____________________ ____________________
____________________ lots of RNAs
mRNA, tRNA, rRNA, siRNA…
RNADNAtranscription
AP Biology
Transcription Making mRNA
transcribed DNA strand = ___________________ enzyme
__________________________
template strand
rewinding
mRNA RNA polymerase
unwinding
DNAC C
C
C
C
C
C
C
C CC
G
GG
G
G G
G G
G
G
GAA
AA A
A
A
A
A
A A
A
AT
T T
T
T
T
T
T
T T
T
T
U U
5
35
3
3
5build RNA 53
AP Biology
Initiation ________________________
binding site before beginning of gene __________________________________ binding site for RNA polymerase
AP Biology
Elongation Match RNA bases to DNA
bases on one of the DNA strands
U
A G GGGGGT T A C A C T T T T TC C C CA A
U
UU
U
U
G
G
A
A
A C CRNA
polymerase
C
C
C
C
C
G
G
G
G
A
A
A
AA
5' 3'
AP Biology
Termination Eventually the RNA transcript is
released and the polymerase detaches (complete mechanism still not fully known)
AP Biology
Eukaryotic genes have junk! Eukaryotic genes are not continuous
___________ = the real gene expressed / coding DNA
___________ = the junk inbetween sequence
eukaryotic DNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
AP Biology
mRNA splicing
eukaryotic DNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
primary mRNAtranscript
mature mRNAtranscript
pre-mRNA
spliced mRNA
Post-transcriptional processing eukaryotic mRNA needs work after transcription ______________________________ ______________________________
edit out introns ______________________________
~10,000 bases
~1,000 bases
AP Biology
Splicing must be accurate No room for mistakes!
a single base added or lost throws off the _______________________
AUG|CGG|UCC|GAU|AAG|GGC|CAU
AUGCGGCTATGGGUCCGAUAAGGGCCAUAUGCGGUCCGAUAAGGGCCAU
AUG|CGG|GUC|CGA|UAA|GGG|CCA|U
AUGCGGCTATGGGUCCGAUAAGGGCCAUAUGCGGGUCCGAUAAGGGCCAU
Met|Arg|Ser|Asp|Lys|Gly|His
Met|Arg|Val|Arg|STOP|
AP Biology
RNA splicing enzymessnRNPs
exonexon intron
snRNA
5' 3'
spliceosome
exonexcisedintron
5'
5'
3'
3'
3'
lariat
exonmature mRNA
5'
AP Biology
Alternative splicing _______________________________________
when is an intron not an intron… different segments treated as exons
AP Biology
A A AA
A3' poly-A tail
mRNA
5'5' cap
3'
G PPP
50-250 A’s
More post-transcriptional processing Need to protect mRNA on its trip from
nucleus to cytoplasm enzymes in cytoplasm attack mRNA
protect the ends of the molecule ________________________________
________________________________