Transcript Lecture Chpt. 17 II Transcript

Central Dogma
DNA
Transcription
RNA
Translation
Polypeptide
WHAT, in the world is
a DOGMA???????
Central Belief
DNA
Transcription
RNA
Translation
Polypeptide
Central Dogma
DNA=
genotype
Transcription
RNA=
the messenger
Translation
initiatio
n
Transcription
unitarea of DNA to be
transcribed (turned
into a protein).
5” --> 3’ direction
from daughter
RNA polymerase enzyme that unzips
DNA & adds mRNA
to the DNA @
promoter point…
transcription begins
here~no primer
needed!!
initiatio
Promotorarea of DNA
in which RNA
polymerase
can bind upstream from
transcription unit
About 100
nucleotides
long.
Holds TATA box
gene
1)Transcription
factors proteins that
bind to DNA
before RNA
polymerase at
the TATA box
gene
proteins that help
bind the
polymerase
2) RNA
polymerase
(enzyme) can now
attach to strand
and double helix
unwinds...
untwists
3)Elongation of
mRNA strand
4)mRNA peels
away from
polymerase
5)DNA re-forms
NOTE: U not T
elongatio
Elongation
• Enzyme moves 5’------> 3’ on RNA strand
• Rate is about 60 nucleotides per second.
6) Terminator
sequencewhen
polymerase hits
this particular
sequence,
transcription ends
termination
IN EUKARYOTES
Pre-RNA is the result
5’
3’
IN EUKARYOTES
Pre-RNA
5’
1) 5’ Cap
-protection against digestive enzymes
degrading the RNA.
- “attach here” symbol (later) for
attachment to ribosome.
3’
IN EUKARYOTES
Pre-RNA
5’
3’
2) 3’ Cap -protection against digestive
enzymes from degrading RNA.
- helps “ship” RNA from nucleus
to ribosome.
RNA
splicing
pre-mRNA +
snRNA’s (small
nuclear RNA)
recognize splice -sites on
pre-mRNA
+
proteins
spliceosome
connects
splice sites on
pre-mRNA
Intron =
cut out of
RNA stays
IN the nucleus
Exon = stays
on & spliced
together.
EXPRESSED
Introns - Function
• Left-over DNA (?)
• Way to lengthen genetic message ~ in other
words... Can a single gene code for more
than one polypeptide?
• Old virus inserts (?)
• Way to create new proteins ~ increases
chances for crossing over to occur... P.S.
MY HEAD IS GOING TO EXPLODE
WITH ALL OF THIS INFORMATION!!
Alternative
Splicing
• The RNA can be spliced into
different mRNA’s.
• Each different mRNA
produces a different
polypeptide.
1965 Dictionary of Amino Acids
mRNA