Transcript No Slide Title

http://members.aol.com/wayneheim/dna-w.jpg
P
P
P
P
P
P
P
P
S A
S T
S G
S C
S T
S C
S G
S T
T S
A S
C S
G S
A S
G S
C S
A S
P
Key Points
:
P
P
P
P
P
P
P
1) Double Helix
2) Sugar-phosphate backbone
3) Nucleotide Rungs
4) Hydrogen bonds
DNA Nucleotides:
Adenine
Cytosine
Thymine
Guanine
Complementary
Base Pairing: DNA
A
G
T
C
RNA: Ribonucleic Acid
1) Single stranded (usually)
2) Nucleotide Uracil replaces Thymine
3) Four species (for this course):
3.1) messenger RNA (mRNA)
3.2) ribosomal RNA (rRNA)
3.3) transfer RNA (tRNA)
3.4) “interfering” RNA (iRNA)
Complementary
Base Pairing: RNA
A
G
U
C
DNA Packaging:
(a) the nucleosome: DNA wraps around
histone proteins.
(b) solenoids: loop of nucleosomes.
Histone
protein
complex
DNA
(c): solenoids form a
loop.
(d): idealized cross
(e): portion of a chromosome
section of a chromosome: without the protein scaffold.
several solenoid loops.
http://users.ntua.gr/sofial/DNA.jpg
(a) DNA replication: strands separate
A
A
T
G
C
A
G
G
T
T
T
A
C
G
T
C
C
A
(b) Synthesis of new, complementary
strands.
Replication
“Stuff”
A
A
T
G
C
A
G
G
T
T
T
A
C
G
T
C
C
A
Terms
Amino acid = basic building block of polypeptide chains.
Phe
Tyr
Ser
Try
Polypeptide chain = series of linked amino acids. AKA
peptide chain.
Arg
Ser
Ala
Phe
Phe
Tyr
Protein = one or more polypeptide chains,
folded and taking on a 3 dimensional
configuration.
Enzyme = a type of protein that speeds up
chemical reactions.
Genetic Code (mRNA)
1) Triplet
2) Redundant
3) Universal
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html
Five Steps in Protein
Synthesis (PETAP):
1) Photocopying
2) Editing
3) Transportation
4) Assembly
5) Packaging
Five Steps in Protein
Synthesis (PETAP):
Common Sense Terms
Scientificese
1) Photocopying = Transcription
2) Editing = Post-transcriptional modification
3) Transportation = Transportation
4) Assembly = Translation
5) Packaging = Post-translational modification
I. Photocopying (Transcription)
Definition:
An RNA strand is synthesized from the DNA
using complementary base pairing.
Process:
1) “Transcription stuff” binds to a promoter region of the DNA.
2) An enzyme “slices” the DNA, making it single stranded.
3) Another enzyme (polymerase) synthesizes a strand of RNA
using one of the DNA strands as a template.
Transcription
“Stuff”
C
A
C
A
A
G
T
T
A
T
G
C
G
G
T
A
RNA
transcript
U
A
C
G
U
C
DNA
G
C
A
G
U
A A
II. Editing
(Post-transcriptional modification)
Definition:
Nonmessage segments in the newly synthesized RNA
strand are edited out.
Process:
1) Enzymes excise the introns (nonmessage segments) from the
RNA strand.
2) Other enzymes splice together the exons (message segments)
giving messenger RNA (mRNA).
Punctuation
marks
exon 1
Punctuation
marks
RNA transcript:
intron 1
exon 2
intron 2
exon 3
exon 2
intron 2
exon 3
Editing:
exon 1
intron 1
Punctuation
marks
exon 1
mRNA
messemger RNA
exon 2
Punctuation
marks
exon 3
III. Transportation (Transportation)
Definition:
mRNA is transported from the nucleus to the cytoplasm
and attaches to a ribosome.
Process:
(same as the definition)
IV. Assembly (Translation)
Definition:
The mRNA codons are “read” and the corresponding amino
acid is added to the polypeptide chain.
Process:
1) A codon enters the “reading frame” of a ribosome.
2) A transfer RNA (tRNA) molecule with the complementary
anticodon binds to the codon of mRNA.
3) The amino acid carried by the tRNA molecule is added to the
polypeptide chain.
3) Steps 1 to 3 are repeated until all codons are “read.”
Transfer RNA
(schematic)
anticodon
“bar code”
A
C
other RNA
amino acid
Trp
C
ribosome
mRNA
U U U A C G C G G U C U
A A A U G C
Phe
U U U A C G C G G U C U
U G C G C C
A A A
Thr
Phe
Thr
A G A
G C C
peptide
chain
A G A
Ser
Arg
tRNA
Arg
Ser
A C C
Trp
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html
http://tidepool.st.usm.edu/pix/protsynth.gif
Posttranslational Modification:
ALWAYS HAPPENS
Polypeptide Folding
Posttranslational Modification:
Sometimes happens
• Folded polypeptide chains join (e.g.,
ALDH-2, hemoglobin)
• add a sugar
• add a fat
Posttranslational Modification:
Protein Activation/Deactivation
• Phosphorylation (add a phoshate group)
• Acetylation (add an acetyl group)
• Alkylation (add a ethyl, methyl group)
• Ubiquitination (add the protein ubiquitin
to an existing protein usually instructs the
cellular machinery to degrade/destroy the
protein)
length in kilobases (kb):
0
10
20
b-like gene cluster on chromosome 11:
yb 2
Promoters:
TATA
CAAT
e
Gg
ATG:
Start
Translation
Here
1
Ag
40
50
yb 1
60
b
d
TAA:
Stop
Translation
Here
Blow up of the
b hemoglobin gene:
Exon 1
ACATTG:
Start transscription
here
30
Intron 1
30
Exon 2
31
Intron 2
104
CodonNumber:
Blow up of Exon 1 of the
b hemoglobin gene:
Nucleotides: GTGCACCTGACTCCTGAGGAGAAGTTGGCC..AGG
Amino Acids: Val His Leu Thr Pro Glu Glu Lys Ser Ala.. Arg
Exon 3
105
Attach a
tail of
multiple
adenines
here
146
CATTGC:
Stop transscription
here
length in kilobases (kb):
0
5
10
15
a-like gene cluster on chromosome 16:
z2
z1
20
ya
1
25
a2
a1
Open window (A) and fly kite (B). String (C) lifts small door (D) allowing moths (E) to escape and eat red flannel shirt (F).
As weight of shirt becomes less, shoe (G) steps on switch (H) which heats electric iron (I) and burns hole in pants (J).
Smoke (K) enters hole in tree (L), smoking out opossum (M) which jumps into basket (N), pulling rope (O) and lifting cage (P),
allowing woodpecker (Q) to chew wood from pencil (R), exposing lead.
Emergency knife (S) is always handy in case opossum or the woodpecker gets sick and can't work.
The Self-Operating Napkin: As you raise spoon of soup (A) to your mouth it pulls string (B), thereby jerking ladle (C) which
throws cracker (D) past parrot (E). Parrot jumps after cracker and perch (F) tilts, upsetting seeds (G) into pail (H).
Extra weight in pail pulls cord (I), which opens and lights automatic cigar lighter (J), setting off sky-rocket (K)
which causes sickle (L) to cut string (M) and allow pendulum with attached napkin to swing back and forth thereby wiping
off your chin.