1. the information carried by a dna molecule is in a. its amino acid sequence
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D.N.A Objective: SWBAT describe the process of transcription and translation IOT understand how proteins are created. 1. The information carried by a DNA molecule is in A. Its amino acid sequence B. The sugars and phosphates forming its backbone - PowerPoint PPT PresentationTRANSCRIPT
D.N.AObjective: SWBAT describe the process of transcription and translation IOT understand how proteins are created
1. The information carried by a DNA molecule is in
A. Its amino acid sequence
B. The sugars and phosphates forming its backbone
C. The order of the bases in the molecule
D. The total number of nucleotides it contains
E. The RNA units that make up a molecule
2. DNA replication occursA. Whenever a cell makes protein
B. To repair gene damage caused by mutation
C. Before a cell divides
D. Whenever a cell needs RNA
E. In the cytoplasm of a eukaryotic cell
3. The complementary strand of DNA to the DNA fragment 5’- GGC ATA CAT – 3” is
A . 3’ – CCG UAU GUA – 5’
B. 3’ – GTA TAT CCG -5’
C. 3’ – ATG TAT GCC – 5’
D. 3’ – CCG TAT GTA – 5’
E. 3’ – CCG AUA GUA – 5’
2007-2008
From Gene to Protein
How Genes Work
What do genes code for?
proteins cells bodies
How does DNA code for cells & bodies? how are cells and bodies made from the
instructions in DNA
DNA
The “Central Dogma” Flow of genetic information in a cell
How do we move information from DNA to proteins?
transcriptiontranslation
replication
proteinRNADNA trait
DNA gets all the glory, but proteins do all the work!
Inheritance of metabolic diseasessuggested that genes coded for enzymeseach disease (phenotype) is caused by non-
functional gene product • lack of an enzyme• Tay sachs• PKU (phenylketonuria)• albinism
Am I just the sum of my proteins?
Metabolism taught us about genes
A B C D E
disease disease disease disease
enzyme 1 enzyme 2 enzyme 3 enzyme 4
metabolic pathway
2007-2008
Transcription
fromDNA nucleic acid language
toRNA nucleic acid language
Transcription
Transcription is the synthesis of messenger RNA (mRNA) from DNA
Occurs in the nucleus DNA does not leave the nucleus
Analogy: blueprints do not get used at the job site when constructing a house
DNA vs. RNA
DNA RNA
Contains:
Adenine, guanine, cytosine, thymine
Contains:
Adenine, guanine, cytosine, uracil
5-carbon sugar is deoxyribose
5-carbon sugar is ribose
Double-stranded Single-stranded
Transcription Making mRNA
transcribed DNA strand = template strand enzyme
• RNA polymerase
template strand
rewinding
mRNA RNA polymerase
unwinding
coding strand
DNAC C
C
C
C
C
C
C
C CC
G
GG
G
G G
G G
G
G
GAA
AA A
A
A
A
A
A A
A
AT
T T
T
T
T
T
T
T T
T
T
U U
5
35
3
3
5build RNA 53
Transcription: Initiation Promoter = a specific
sequence of DNA (starting point)
RNA polymerase binds to the promoter on the DNA molecule
Transcription factors (proteins) bind to promoter region to help RNA polymerase find the starting point.
RNA polymerase then separates the 2 DNA strands
Transcription: Elongation As RNA polymerase
moves along the DNA, it untwists the double helix and separates the strands
RNA polymerase adds nucleotides to the 3’ end of the mRNA molecule Follows the base-pairing
rules
G = C
A = U
Matching bases of DNA & RNA
Match RNA bases to DNA bases on one of the DNA strands
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
5' 3'
Transcription: Termination
Termination signal = sequence of bases in DNA molecule that tell RNA polymerase to stop transcription“finish line” in a race
mRNA is released from the DNA
RNA Modifications
In eukaryotes, mRNA is edited before it’s sent out of the nucleus
2 major types of modifications:Alteration of mRNA endsRNA splicing
RNA Splicing Genes have stretches of nucleotides that don’t code for anything
“junk DNA” Noncoding sequence = introns
“intervening sequences” Coding regions = exons During RNA splicing, the introns are removed by enzymes and the
exons are joined together
A A AA
A3' poly-A tail
mRNA
5'5' cap
3'
G PPP
50-250 A’s
Need to protect mRNA on its trip from nucleus to cytoplasmenzymes in cytoplasm attack mRNA
• protect the ends of the molecule• add 5 cap• add poly-A tail
• longer tail, mRNA lasts longer: produces more protein
Alteration of mRNA Ends
Translation
fromnucleic acid language
toamino acid language
How does mRNA code for proteins?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Met Arg Val Asn Ala Cys Alaprotein
?
ATCG
AUCG
AUGCGUGUAAAUGCAUGCGCCmRNA
mRNA codes for proteins in triplets
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
Met Arg Val Asn Ala Cys Alaprotein
?
codon
Cracking the code1960 | 1968
Crickdetermined 3-letter (triplet) codon system
Nirenberg & Khorana
WHYDIDTHEREDBATEATTHEFATRATWHYDIDTHEREDBATEATTHEFATRAT
Nirenberg (47) & Khorana (17) 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
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
How are the codons matched to amino acids?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
aminoacid
tRNA anti-codon
codon
5 3
3 5
3 5
UAC
MetGCA
ArgCAU
Val
mRNA
From gene to protein
DNAtranscription
nucleus cytoplasm
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
ribosome
traitaa
proteintranslation
DNA strand mRNA strand – codon Amino acid
CGC
AGT
GAC
GCG
UCA
CUG
Serine
Alanine
Leucine
mRNA
From gene to protein
DNAtranscription
nucleus cytoplasm
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
ribosome
traitaa
proteintranslation
How are the codons matched to amino acids?
TACGCACATTTACGTACGCGGDNA
AUGCGUGUAAAUGCAUGCGCCmRNA
aminoacid
tRNA anti-codon
codon
5 3
3 5
3 5
UAC
MetGCA
ArgCAU
Val
Transfer RNA structure “Clover leaf” structure
anticodon on “clover leaf” endamino acid attached on 3 end
Loading tRNA Aminoacyl tRNA synthetase
enzyme which bonds amino acid to tRNA bond requires energy
• ATP AMP• bond is unstable• so it can release amino acid at ribosome easily
activatingenzyme
anticodontRNATrp binds to UGG condon of mRNA
Trp Trp Trp
mRNAA C CU GG
C=O
OHOH
H2OO
tRNATrp
tryptophan attached to tRNATrp
C=O
O
C=O
Ribosomes Facilitate coupling of
tRNA anticodon to mRNA codonorganelle or enzyme?
Structureribosomal RNA (rRNA) & proteins2 subunits
• large• small E P A
Ribosomes
Met
5'
3'
UUA 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
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 MetMet Met
PE AmRNA5' 5' 5' 5'
3' 3' 3'3'
U UA AAACC
CAU UG G
GUU
A AAAC
CC
AU UG GGU
UA
AAAC
CC
AU UG GGU U
A AACCA U UG G
G AC
ValSer
AlaTrp
releasefactor
AA A
CCU UGG 3'
Protein targeting Signal peptide
address label
Destinations: secretion nucleus mitochondria chloroplasts cell membrane cytoplasm etc…start of a secretory pathway
Can you tell the story?
DNA
pre-mRNA
ribosome
tRNA
aminoacids
polypeptide
mature mRNA
5' GTP cap
poly-A tail
large ribosomal subunit
small ribosomal subunit
aminoacyl tRNAsynthetase
E P A
5'
3'
RNA polymerase
exon introntRNA
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
eukaryoticDNA
exon = coding (expressed) sequence
intron = noncoding (inbetween) sequence
intronscome out!
Transcription & translation are simultaneous in bacteria DNA is in
cytoplasmno mRNA
editing ribosomes
read mRNA as it is being transcribed
Translation in Prokaryotes
Translation: prokaryotes vs. eukaryotes Differences between prokaryotes &
eukaryotestime & physical separation between
processes• takes eukaryote ~1 hour
from DNA to proteinno RNA processing