Disclaimer: This is not my own Powerpoint Presentation. Credits to Mindanao State University - General Santos City - College of Natural Science and Mathematics.
Pests of soyabean_Binomics_IdentificationDr.UPR.pdf
Central Dogma of Life
1.
2. Organelles
nucleus
ribosomes
endoplasmic reticulum
(ER)
Golgi apparatus
vesicles
Making proteins
small
ribosomal
subunit
large
ribosomal
subunit
cytoplasm
mRNA
nuclear pore
3. The “Central Dogma”
Flow of genetic information in a cell
How do we move information from DNA to proteins?
transcription
translation
replication
proteinRNADNA trait
DNA gets
all the glory,
but proteins do
all the work!
4.
5. DNA Replication
semiconservative
Watson and Crick base
pairing maintained
Synthesis in 5’ to 3’ direction
A primer is needed for
initiation
a complex process involving
several enzymes and
proteins (Replisome)
6. Copying DNA
Replication of DNA
base pairing allows
each strand to serve
as a template for a
new strand
7. Models of DNA Replication
Alternative models
so how is DNA copied?
conservative semiconservative dispersive
8.
9. Proteins and Enzymes
DNA polymerase I – 5’ to 3’ polymerization
– 3’ to 5’ proofreading
– 5’ to 3’ exonuclease activity
DNA Polymerase II – DNA Repair functions
DNA Polymerase III – primary replication enzyme
Helicase
Single-strand Binding Proteins
Primase
Ligase
Topoisomerase
13. Transcription in Eukaryotes
3 RNA polymerase enzymes
RNA polymerase 1
only transcribes rRNA genes
makes ribosomes
RNA polymerase 2
transcribes genes into mRNA
RNA polymerase 3
only transcribes tRNA genes
each has a specific promoter sequence
it recognizes
14. Transcription in Eukaryotes
Initiation complex
transcription factors bind
to promoter region
upstream of gene
suite of proteins which bind
to DNA
turn on or off transcription
TATA box binding site
recognition site for
transcription factors
transcription factors
trigger the binding of RNA
polymerase to DNA
16. A A A
A
A3' poly-A tail
mRNA
5'
5' cap
3'
GP
PP
50-250 A’s
Post-transcriptional processing
eukaryotic DNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
primary mRNA
transcript
mature mRNA
transcript
pre-mRNA
spliced mRNA
Primary transcript (pre-mRNA)
eukaryotic mRNA needs work after transcription
mRNA processing (making mature mRNA)
mRNA splicing = edit out introns
protect mRNA from enzymes in cytoplasm
add 5′ cap
add polyA tail
~10,000 bases
~1,000 bases
17. Splicing must be accurate
No room for mistakes!
splicing must be exactly accurate
a single base added or lost throws off the
reading frame
AUG|CGG|UCC|GAU|AAG|GGC|CAU
AUGCGGCTATGGGUCCGAUAAGGGCCAU
AUGCGGUCCGAUAAGGGCCAU
AUG|CGG|GUC|CGA|UAA|GGG|CCA|U
AUGCGGCTATGGGUCCGAUAAGGGCCAU
AUGCGGGUCCGAUAAGGGCCAU
Met|Arg|Ser|Asp|Lys|Gly|His
Met|Arg|Val|Arg|STOP|
18. Splicing enzymes
snRNPs
exonexon intron
snRNA
5' 3'
spliceosome
exon
excised
intron
5'
5'
3'
3'
3'
lariat
exon
mature mRNA
5'
No,
not smurfs!
“snurps”
snRNPs
small nuclear RNA
proteins
Spliceosome
several snRNPs
recognize splice
site sequence
cut & paste
19. Prokaryote vs. Eukaryote genes
Prokaryotes
DNA in cytoplasm
circular
chromosome
naked DNA
no introns
Eukaryotes
DNA in nucleus
linear
chromosomes
DNA wound on
histone proteins
introns vs. exons
eukaryotic
DNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
introns
come out!
23. Transcription & translation are simultaneous
in bacteria
DNA is in
cytoplasm
no mRNA
editing
ribosomes
read mRNA
as it is being
transcribed
Translation in Prokaryotes
24. Translation: prokaryotes vs. eukaryotes
Differences between prokaryotes &
eukaryotes
time & physical separation between
processes
takes eukaryote ~1 hour
from DNA to protein
RNA processing
26. mRNA
From gene to protein
DNA
transcription
nucleus cytoplasm
mRNA leaves
nucleus through
nuclear pores
proteins synthesized
by ribosomes using
instructions on mRNA
aa
aa
aa
aa
aa
aa
aa
aa
ribosome
protein
translation
27. How does mRNA code for proteins?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Met Arg Val Asn Ala Cys Alaprotein
?
How can you code for 20 amino acids
with only 4 nucleotide bases (A,U,G,C)?
4
4
20
ATCG
AUCG
29. Cracking the code
1960 | 1968
Crick
determined 3-letter (triplet) codon system
Nirenberg & Khorana
WHYDIDTHEREDBATEATTHEFATRATWHYDIDTHEREDBATEATTHEFATRAT
Nirenberg & Khorana
determined mRNA–amino acid match
added fabricated mRNA to test tube of
ribosomes, tRNA & amino acids
created artificial UUUUU… mRNA
found that UUU coded for phenylalanine (phe)
30. The code
Code for ALL life!
strongest support for
a common origin for
all life
Code is redundant
several codons for
each amino acid
3rd base “wobble”
Start codon
AUG
methionine
Stop codons
UGA, UAA, UAG
Why is the
wobble good?
31. How are the codons matched to
amino acids?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
amino
acid
tRNA
anti-codon
codon
5′ 3′
3′ 5′
3′ 5′
UAC
Met
GCA
Arg
CAU
Val
32. mRNA
From gene to protein
DNA
transcription
nucleus
cytoplasm
aa
aa
aa
aa
aa
aa
aa
aa
ribosome
protein
translation
aa
33. Transfer RNA structure
“Clover leaf” structure
anticodon on “clover leaf” end
amino acid attached on 3′ end
34.
35. Ribosomes
Facilitate coupling of
tRNA anticodon to
mRNA codon
organelle or enzyme?
Structure
ribosomal RNA (rRNA) & proteins
2 subunits
large
small E P A
36. Ribosomes
Met
5'
3'
U
U
A C
A G
APE
A site (aminoacyl-tRNA site)
holds tRNA carrying next amino acid to
be added to chain
P site (peptidyl-tRNA site)
holds tRNA carrying growing
polypeptide chain
E site (exit site)
empty tRNA
leaves ribosome
from exit site
37. Building a polypeptide
Initiation
brings together mRNA, ribosome
subunits, initiator tRNA
Elongation
adding amino acids based on
codon sequence
Termination
end codon 123
Leu
Leu Leu Leu
tRNA
Met Met
Met Met
PE A
mRNA
5' 5' 5' 5'
3' 3' 3'
3'
U UA AA
AC
C
C
AU UG G
GU
U
A
AA
AC
C
C
AU UG G
GU
U
A
AA
AC
C
C
AU UG G
GU U
A
AAC
CAU UG G
G
A
C
Val
Ser
Ala
Trp
release
factor
A
A A
CC
U UGG
3'
38. Can you tell
the story?
DNA
pre-mRNA
ribosome
tRNA
amino
acids
polypeptide
mature mRNA
5' cap
polyA tail
large ribosomal subunit
small ribosomal subunit
aminoacyl tRNA
synthetase
E P A
5'
3'
RNA polymerase
exon intron
tRNA
To get from the chemical language of DNA to the chemical language of proteins requires 2 major stages:
transcription and translation
eukaryotic RNA is about 10% of eukaryotic gene.
Walter Gilbert hypothesis:
Maybe exons are functional units and introns make it easier for them to recombine, so as to produce new proteins with new properties through new combinations of domains.
Introns give a large area for cutting genes and joining together the pieces without damaging the coding region of the gene…. patching genes together does not have to be so precise.
Strong evidence for a single origin in evolutionary theory.