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Regents Biology
Chapter 8: From DNA to ProteinSection 8.4 - Transcription
Regents Biology
What do we know so far? DNA
DNA is the genetic information Located in Nucleus (protected in vault)
Proteins all living things made of proteins Proteins made by ribosomes in cytoplasm proteins run living organisms
example – enzymes
So the DNA moleculeis the instructions
for making proteins!!!
I get it!!!
DNA is likea blueprint!!
Regents Biology
But there is a problem………. Need to get the blueprint information (DNA
message) from nucleus to cytoplasm
We need
a messenger
We need
mRNA!!!!
Regents Biologycytoplasm
nucleus
build proteins
DNA
RNA
Who is the mRNA messenger? messenger RNA
mRNA
Regents Biology
mRNA
The “Central Dogma” – information flows in one direction
DNA
transcription
cell nucleus cell cytoplasm
proteintranslation
trait(phenotype)
Regents Biology
You have to know differences between DNA and RNA for my test and EOC!!!!
DNA deoxyribose sugar nitrogen bases
G, C, A, T T = thymine
T : A C : G
double stranded
RNA ribose sugar nitrogen bases
G, C, A, U U = uracil
U : A C : G
single stranded
Regents Biology
Transcription is making mRNA from DNA
Double stranded DNA unzips by helicase enzyme
A G GGGGGT T A C A C T T T T TC C C CA A
Regents Biology
Now that DNA is unzipped; enzyme RNA polymerase attaches base pairs
A G GGGGGT T A C A C T T T T TC C C CA A
Transcription is making mRNA from DNA
Regents Biology
RNA polymerase will match RNA bases to DNA bases on one of the DNA strands
Notice NO THYMINE!!!!!!!
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
Transcription is making mRNA from DNA
Regents Biology
U instead of T is matched to A in mRNA
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Transcription is making mRNA from DNA
Once mRNA molecule is completed it leaves nucleus and goes to cell cytoplasm
Regents Biology
Chapter 8: From DNA to ProteinSection 8.5 - Translation
Regents Biology
nucleus
DNA instructions remain in nucleus
and we have to send message out
mRNA has the instructions for building
proteins from DNA
U C CCCCCA A U G U G A A A A AG G G GU U
Regents Biology
Proteins are built as chains of amino acids
What reads RNA? need a mRNA reader!
aa
aa
aa
aa
aa
aa
aa
Regents Biology
RNA to protein mRNA leaves nucleus mRNA goes to ribosomes in cytoplasm amino acids are linked bc of mRNA message proteins built from sequence of amino acids
aa aa aa aa aa aa aa aa
Now lets look at bigger picture!!!mRNA
U C CCCCCA A U G U G A A A A AG G G GU U
Regents Biology
aa
aa
aaaa
aa
aa
aa
mRNA
RNA to protein bigger picture
DNA
transcription
Cell nucleus
Cell cytoplasm
protein
translation
trait
U C CCCCCA A U G U G A A A A AG G G GU UribosomemRNA leaves
nucleus through nuclear pores
proteins synthesized by ribosomes using instructions on mRNA
Regents Biology
How does mRNA code for proteins?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
protein
?
How can you code for 20 amino acids with only 4 nucleotide bases (A,U,G,C)?
think letters
in alphabet
Regents Biology
AUGCGUGUAAAUGCAUGCGCCmRNA
mRNA codes for proteins in triplets
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Met Arg Val Asn Ala
Cys Alaprotein
Ribosomes read mRNA in blocks of 3 nucleotides called a “Codon”
codons
ribosome
Regents Biology
How are the codons matched to amino acids?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
aminoacid
tRNA anti-codonUAC
Met
GCA
ArgCAU
Val
Regents Biology
Start codon AUG
Stop codons UGA, UAA, UAG
The mRNA code
codon formethionine (Met)
codon forleucine (Leu)
Regents Biology
aa
aa
aaaa
aa
aa
aa
mRNA
Summarize whole process of “DNA to Proteins”
DNA
transcription
Cell nucleus Cell cytoplasm
protein
translation
trait
U C CCCCCA A U G U G A A A A AG G G GU Uribosome
tRNA
aa
Regents Biology
proteinaa
aa
aa
aa
aa
aa
aa
aaaa
aa
aa
transcription
Cell cytoplasm
Cell nucleus
translation
trait
Different view of “DNA to Proteins”
Regents Biology
DNA
transcription
ribosome
tRNA
aminoacids
protein
translation
mRNA
Regents Biology
Section 8.6: Gene Expression and
Gene Regulation
Regents Biology
The BIG Questions… How are our traits turned “on”
or “off”?
Regents Biology
How do cells control Gene Expression? Cells turn genes “on” & “off” by controlling
transcription Remember what RNA Polymerase did?
Regents Biology
How do cells control Gene Expression?
For RNA Polymerase to do its job it has to attach to the DNA molecule
Promoter - area of DNA where RNA polymerase binds. Also area where the “Gene” sequence begins.
Operator – area of DNA that turns gene “on” or “off”. It’s the switch
Lets take a closer
look at how this
works!
Regents Biology
Gene regulation using “lac Operon Model”
The lac Operon uses a repressor protein as a stop sign until gene is ready to be made
Regents Biology
Do you want all your genes turned on if you just need to make one trait? NO!!!!!
Eukaryotic RNA is processed before leaving nucleus. “RNA Splicing”
Introns – gene segments that are cut out before mRNA leaves nucleus
Exons – gene segments that attach to each other that will code for mRNA
Regents Biology
http://www.pbslearningmedia.org/
resource/tdc02.sci.life.gen.proteinsynth/
from-dna-to-protein/