PS
PS
PS
PS
PS
PS
PS
PS
PSP
SP
SP
SP
SP
SP
SP
S
T A
G C
C G
A T
T A
C G
G C
T A
Key Points:
1) Double Helix2) Sugar-phosphate backbone3) Nucleotide Rungs4) Hydrogen bonds
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)
Histoneproteincomplex
DNA
(a) the nucleosome: DNA wraps aroundhistone proteins.
(b) solenoids: loop of nucleosomes.
(c): solenoids form aloop.
(d): idealized crosssection of a chromosome:several solenoid loops.
(e): portion of a chromosomewithout the protein scaffold.
DNA Packaging:
TGC
ACG
A TA TG
TC
GG
AT
CC
TA
A
A TG CG CT A
CAGCCTAGGATT
(a) DNA replication: strands separate
TGC
ACG
A TA TG
TC
GG
ATT
ACGC
GTAA
TAT
A TG CG CT A
CAGCC
AT
TA
CG
CG
TA
AT
AT
(b) Synthesis of new, complementarystrands.
Replication“Stuff”
TermsAmino acid = basic building block of polypeptide chains.
Polypeptide chain = series of linked amino acids. AKA peptide chain.
Protein = one or more polypeptide chains, folded and taking on a 3 dimensional configuration.
Enzyme = a type of protein that speeds up chemical reactions.
TryTyrPhe Ser
PheSerArg Ala Phe Tyr
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html
Genetic Code (mRNA)
1) Triplet2) Redundant3) Universal
Five Steps in ProteinSynthesis (PETAP):
1) Photocopying
2) Editing
3) Transportation
4) Assembly
5) Packaging
Five Steps in ProteinSynthesis (PETAP):
1) Photocopying
2) Editing
3) Transportation
4) Assembly
5) Packaging
= Transcription
= Post-transcriptional modification
= Transportation
= Translation
= Post-translational modification
Common Sense Terms Scientificese
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.
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).
exon 1 intron 1 exon 2 intron 2 exon 3
Punctuationmarks
PunctuationmarksRNA transcript:
exon 1 intron 1 exon 2 intron 2 exon 3
Editing:
exon 1
Punctuationmarks
exon 2 exon 3
Punctuationmarks
mRNAmessemger RNA
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.
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.”
2) A transfer RNA (tRNA) molecule with the complementary anticodon binds to the codon of mRNA.
Ser
A G A
U A C GU G
Phe
A A AU C G
U G C
Thr
U UC U A C GU G
PheA A A
U C GU G C
Thr
U UC
Arg
G C C
Arg
G C C
Ser
A G A
Trp
C CA
mRNA
tRNA
ribosome
peptidechain
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)
2 1G A -like gene cluster on chromosome 11:
10 20 30 40 50 600
length in kilobases (kb):
Blow up of Exon 1 of the hemoglobin gene:
GTGCACCTGACTCCTGAGGAGAAGTTGGCC..AGGNucleotides:Val His Leu Thr Pro Glu Glu Lys Ser Ala.. ArgAmino Acids:
ACATTG:Start trans-
scriptionhere
Exon 1 Exon 2 Exon 3Intron 1 Intron 2
Promoters: TATA CAAT
ATG:Start
TranslationHere
TAA:Stop
TranslationHere
CATTGC:Stop trans-scription
here
Attach atail of
multipleadenines
here
Blow up of the hemoglobin gene:
1 30 31 104 105 146CodonNumber:
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.