Transcript Slide 1

Cell
DNA
Transcription
Translation
mRNA
Ribosome
Polypeptide
(protein)
Flow of Information:
DNA
RNA
Transcription
Protein
Translation
Transcription: DNA is copied into
messenger RNA (mRNA).
This messenger brings code from nucleus to
ribosome where translation occurs.
Transcription process:
•DNA
unzips and one strand serves as a
template.
•The RNA bases attach to the DNA
template, thus assembling mRNA.
•mRNA leaves the nucleus and travels to
the ribosome in the cytoplasm.
Cytoplasm
DNA
Transcription
RNA
RNA
Processing
mRNAG
G
AAAAAA
Nucleus
Export
AAAAAA
Step 1: Hydrogen bonds
between complimentary
bases break
DNA “unzips”
Step 2: DNA strands
pull apart from each other
Step 3:
RNA nucleotides in the
nucleus match up with
only one side of the
“unzipped” DNA, the
sense strand
-each “unzipped’ strands
forms a template for a
mRNA strand
RNA nucleotide
Step 4:
RNA nucleotides
continue to match up
with “unzipped”
DNA
until the message
is completely
transcribed
mRNA strand
One side of DNA strand
mRNA strand
Step 4:
mRNA strand
breaks off from
the DNA strand
One side of DNA strand
Step 5:
mRNA strand
leaves the
nucleus for the
ribosome
Step 6: Once the mRNA
leaves, the DNA “zips”
back together
Transcription
transcription2
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mRNA dictates the amino acid sequence of a
protein.
1 Strand RNA  Amino Acid Chain  Protein
Translation process:
Translation: mRNA codes for a
polypeptide chain or protein.
Each combination of 3 nucleotides on
mRNA is called a codon:
Each codon specifies a particular amino
acid.
Transfer RNA (tRNA): carries amino
acids to mRNA in ribosome to
assemble an amino acid chain –
protein.
tRNA molecules have 2 important
sites of attachment.
•One site, called the anticodon,
binds to the codon on the
mRNA molecule.
•The other site attaches to a
particular amino acid.
Methionine
What is the codon that this
tRNA will bind to?
16 Pu
17
9
A
17:1
13 12 Py 10
1
2
3
4
5
6
U* 7
A
C
C
73
72
71
70
69
68
67
66
Py59A*
65 64 63 62 C
49 50 51 52 G T
G*
22 23 Pu 25
G
26
2020:120:2A
27
1
28
29
30
31
Py*
Anticodon
Py
47:16
47:15
43 44
42 45
41 46
47
40
47:1
39
38
Pu*
U
34
U 35
C
A 36
Pu
y
C
What are the anti-codons that will bind to these codons?
During protein
synthesis, the
anticodon of a tRNA
molecule base pairs
with the appropriate
mRNA codon.
Ribosome:
•Protein
synthesis starts when the two
rRNA subunits bind to mRNA.
•The
initiator codon AUG binds to the first
anticodon of tRNA, signaling the start of
a protein.
Ribosome:
•The anticodon of another tRNA binds to
the next mRNA codon, bringing the 2nd
amino acid of the protein.
•As each anticodon & codon bind together
a peptide bond forms between the two
amino acids.
•The
protein chain continues to grow until
a stop codon reaches the ribosome, which
results in the release of the new protein
and mRNA, completing the process of
translation.
DNA
Transcribed
Onto
mRNA
1 CODON
(mRNA)
1 ANTICODON
(tRNA)
1 amino acid
http://www.youtube.com/watch?v=1NkLqjQkGHU&feature=related
http://www.hhmi.org/biointeractive/dna/DNAi_translation_vo2.html
•20
different amino acids are used to
make proteins.
•4 bases in RNA and 3 bases make up one
codon: thus 43 (4x4x4)=64 total codons
possible.
fMet
Large
subunit
E
P
A
UAC
5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT
GCA...TAAAAAA
Small mRNA
subunit
3’
Polypeptide
Arg
Met
Phe
Leu
Ser
Ribosome
Aminoacyl tRNA
Gly
E
P
A
CCA
5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT
GCA...TAAAAAA
mRNA
3’
Polypeptide
Met
Phe
Leu
Ser
Gly
Arg
Aminoacyl tRNA
Ribosome
E
P
A
CCA UCU
5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT
GCA...TAAAAAA
mRNA
3’
H
AMINE
H
O
N
ACID
C
C
ANYTHINGR
H
Amino Acid
Alanine
OH
H
H
Serine
H
O
N
C
OH
H
C
H
H
H
H2O
H
H
C
H
C
HO
H
O
C
C
C
C
H
N
H
H
N
H
C
O
H
O
N
C
H
H
H HO
C
H
C
H
OH
OH
Polypeptide
Met
Phe
Leu
Ser
Gly
Arg
Ribosome
E
P
A
CCA UCU
5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT
GCA...TAAAAAA
mRNA
3’
Polypeptide
Met
Phe
Leu
Ala
Ser
Gly
Aminoacyl tRNA
Arg
Ribosome
E
P
A
CCA
UCU
5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT
GCA...TAAAAAA
mRNA
3’
Polypeptide
Met
Phe
Leu
Ser
Gly
Arg
Ribosome
E
Ala
P
A
UCU CGA
5’GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT
GCA...TAAAAAA
mRNA
http://highered.mcgrawhill.com/sites/0072943696/student_view0/chapter3/animation__protein_sy
nthesis__quiz_3_.html
3’
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A change in the nitrogenous base sequence
of DNA; that change can cause a change in
the product coded for by the mutated gene.
Neutral
Hazardous
Beneficial
What happens when you get insertions or deletions of bases in the DNA
sequence?
Usually you end up with a mess.
THE BIG FAT CAT ATE THE RAT AND GOT ILL
Deletion of one base
THE IGF ATC ATA TET HER ATA NDG OTI LL
And its all pops and buzzes!!
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Base Substitution
- One base pair in DNA is replaced with a
different base pair (point mutation)
Deletion
- A piece of DNA breaks off and is lost
Duplication and Translocation
- A piece of DNA breaks off and is
incorporated into another strand of DNA
Frameshift
- Deletion or Addition results in a shift in
the DNA frame
Silent mutation
- codon is changed, but still codes for the
same amino acid: serine codons – TCT,
TCG, TCA, and TCC
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http://www.hhmi.org/biointeractive/dna/D
NAi_damage_mutation.html
http://www.hhmi.org/biointeractive/dna/D
NAi_sicklecell.html