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• DNA makes ____ makes ________.
• Proteins are the links between ___________ and ________________.
From DNA to Proteins Chapter 13
growing RNA transcript5’
3’5’
3’
direction of transcription
• The bridge between DNA and ________ synthesis is RNA.
• RNA differs from DNA
1. RNA contains _____as its sugar (not deoxyribose)
2. _______ replaces thymine.
AGTCAT becomes AGUCAU
3. An RNA molecule almost always consists of a _______strand.
___________ and ___________ are the two main processes linking gene to protein
Fig. 6.8a
This is an H in DNA
4 types of RNA
• ________ - carries info for protein production
• _______-transport amino acids in translation
• _______- part of ribosome, has role in translation
• ________ - splicing mRNA
UAA
AUGPre-mRNA
3. _____________
NH2 COO- Protein7. ________________
AUG
AAAAAA…..
D CA BE
7mG
UAA
F
4._________
Chromosome- 1.5 x 108 base pairs containing about 3000 genes
0.4% of a chromosome, containing 10 genes
ATGDNA
CB EDFTAA
= 1. ________________
= 2. ________________
5’3’
3’5’
+1 AATAAA
5. ______ 6. ____________
• ____________ - DNA is the template for RNA, usually __________ RNA (mRNA).
Fig. 17.2a
•____________________ - the information contained in the order of nucleotides in mRNA is used to determine the __________ sequence of a polypeptide.
-Translation occurs at ____________.
• The basic mechanics of transcription and translation are ________ in eukaryotes and prokaryotes.
• In the __________, three consecutive bases specify an amino acid, creating 43 (64) possible ________.
• The genetic instructions for a polypeptide chain are written in DNA as a series of three- __________words.
In the genetic code, nucleotide triplets specify amino acids
1. ___ of 64 triplets code for amino acids.
• AUG codes for the methionine and ____ of translation.
Fig. 17.4
•Three codons –___, ___ and
____ do not code amino acids but signal the termination of translation.
The genetic code
2. The genetic code is __________but not_ _________ .
• Typically several different codons specify a given amino acid
• Any one codon indicates _ __________ amino acid.
Know how to
read this chart!!
The genetic code (cont.)
A ______________ is established at the translation start
UUACGAUGGAUUCAAACGUCAGGGCCUAAGGCUAG
Start codon
AspStop
codon
Met AsnSer ArgVal AlaRNA
Summary- The genetic code uses_ ____________________, or codons, each of which is translated into a specific amino acid.
5’ 3’
Know how to
read this chart!!
• The genetic code is nearly ______________ , from bacteria to mammals
Thus, we can synthesize bacterial proteins in ______________
Exceptions do exist- they use slightly altered genetic codes:
1.single-celled eukaryotes like Paramecium.
2. certain mitochondria and chloroplast ____________
• Messenger RNA is transcribed from the template strand of a gene by ________________.
• __________________________ :
• separates the DNA strands
• bonds the RNA nucleotides as they base-pair along the DNA template.
DNA3’ 5’
5’ RNA 3’
What actually makes the RNA?
•Answer- Specific sequences of nucleotides called the _________ mark where gene transcription begins
What marks the start of transcription??
•In prokaryotes, RNA polymerase can recognize and bind ______________ to the promotor region.
•In eukaryotes, proteins called ___________ first bind the promotor region, especially a __________ , then RNA polymerase II binds
Transcript Modification
unit of transcription in a DNA strand
exon intron
mature mRNA transcript
poly-A tail
5’
5’ 3’
3’
snipped out
snipped out
exon exonintron
cap
transcription into pre-mRNA
3’ 5’
Transport to cytoplasm
UAA
AUGhnRNA
Transcription
NH2 COO- ProteinTranslation
AUG
AAAAAA…..
D
RNA SplicingpolyA tail,cap
CA BE
7mGmRNA
UAA
F
Regulatory DNA sequences
Chromosome- 1.5 x 108 base pairs containing about 3000 genes
0.4% of a chromosome, containing 10 genes
Overview of eukaryotic transcription/translation15.3
15.215.1
14
13.3
13.11211
11.111.2
12
13.113.213.3
14
15
21
2223.1
23.3
31.131.231.3
3233.133.334
35.135.3
35.2
33.2
23.2
13.2
ATGDNA
CB EDFTAA
= exon= intron
5’3’
3’5’
Template strand+1
AAUAAA
• _____________ (tRNA) - transfers amino acids from the cytoplasm’s pool to a ________________.
• The ribosome adds each amino acid carried by tRNA to the growing end of the _________________ chain.
codon in mRNA
anticodonin tRNA
amino acid OH
tRNA molecule’s attachment site for amino acid
How do proteins read the RNA molecule??
Answer-the ___________________
ribosome
tRNA
A tRNA molecule
• Is about ___ nucleotides long
• Contains attachment site for an amino acid.
• Contains a loop with the ___________
Fig. 17.13
The anticodon base-pairs with a complementary codon on mRNA.
If the codon on mRNA is UUU, a tRNA with a ______ anticodon and a tRNA carrying phenylalanine will bind to it.
5’3’
Translation can be divided into three ______ 1. initiation
2. _________
3. termination
1. Initiation
a. Small ribosomal subunit binds mRNA
b. Initiator tRNA (with methionine) is attached to start codon
Fig. 17.17
Translation
2. Elongation - Amino acid sequentially added
c. Translocation - the ribosome moves the tRNA with the attached polypeptide from the A site to the P site.
Translation
3. Termination occurs when ribosome reaches a _____codon.
• A ____________ binds to the stop codon and hydrolyzes the bond between the polypeptide and its tRNA in the P site.
Fig. 17.19
Translation
• Multiple ribosomes, polyribosomes, may trail along the same _______.
• A ribosome requires less than a ________ to translate an average-sized mRNA into a polypeptide.
Fig. 17.20
Other translation facts
OverviewTranscription
Translation
mRNA rRNA tRNA
Mature mRNA transcripts
ribosomal subunits
mature tRNA
Point mutations can affect protein structure and function• __________ are changes
in the genetic material of a cell (or virus).
• include large-scale mutations in which _____ segments of DNA are affected (translocations, duplications, and inversions).
• A chemical change in just one base pair of a gene causes a _______________
In sickle cell, a single T to A mutation changes amino acid from glu to val
•_________ - alterations of nucleotides still indicate the same amino
acids because of redundancy in the genetic code.
•Many other mutations cause no effect in function
• Other base-pair substitutions cause a readily detectable change in a protein.
• _______ mutations are those that still code for an amino acid but change the indicated amino acid.
• _______ mutations change an amino acid codon into a _____ codon, nearly always leading to a nonfunctional protein.
Fig. 17.24
• Insertions and ______ are additions or losses of nucleotide pairs in a gene.
• These have a _________ effect on the resulting protein more often than substitutions do.
• Unless these mutations occur in multiples of ____, they cause a ________ mutation.
• All the nucleotides downstream of the deletion or insertion will be improperly grouped into codons.
• The result will be extensive missense, ending sooner or later in nonsense - premature termination.
Fig. 17.24
______________Mutation
ARGININE GLYCINE TYROSINE TRYPTOPHAN ASPARAGINE
ARGININE GLYCINE LEUCINE GLUTAMATELEUCINE
mRNA
PARENTAL DNA
amino acid sequence
altered mRNA
BASE INSERTION
altered amino acid sequence
Really bad!!
• __________ are chemical or physical agents that interact with DNA to cause mutations.
• ________agents include high-energy radiation like X-rays and ultraviolet light.
__________ mutagens may operate in several ways.
• As base ____________ that may be substituted into DNA, but that pair incorrectly during DNA replication.
• Interfere with DNA replication by inserting into DNA and distorting the ______________.
• Cause chemical changes in bases that change their pairing properties.
Fig. 13.14, p. 210
TRANSCRIPTION Unwinding of gene regions of a DNA molecule
Pre mRNA Transcript Processing
mRNA rRNA tRNA
TRANSLATION
FINAL PROTEIN
Destined for use in cell or for trasport
Convergence of RNAs
Synthesis of a polypetide chain at binding sites for mRNA and tRNA on the surface of an intact ribosome
Cytoplasmic pools of amino acids, tRNAs, and ribosomal subunits
Mature mRNA transcripts
protein subunits
ribosomal subunits
mature tRNA
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