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From DNA to Proteins
• DNA makes ____ makes
________.
5’
Chapter 13
growing RNA transcript
3’
5’
3’
• Proteins are the links
between ___________ and
________________.
direction of transcription
___________ and ___________ are the two
main processes linking gene to protein
• 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.
This is an H in DNA
Fig. 6.8a
4 types of RNA
• ________ - carries info for protein production
• _______-transport amino acids in translation
• _______- part of ribosome, has role in translation
• ________ - splicing mRNA
Chromosome- 1.5 x 108 base pairs containing about 3000 genes
0.4% of a chromosome, containing 10 genes
= 1. ________________
5’
3’
ATG B
C
D
E
F
TAA
AATAAA
+1
= 2. ________________
3’
5’
DNA
3. _____________
AUG
Pre-mRNA
4._________
UAA
5. ______
AB
7mG
AUG
CD
6. ____________
E
F
AAAAAA…..
UAA
7. ________________
NH2
COO-
Protein
• ____________ - DNA is the template for RNA,
usually __________ RNA (mRNA).
•____________________ - 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.
Fig. 17.2a
In the genetic code, nucleotide triplets
specify amino acids
• 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.
The genetic code
1. ___ of 64 triplets code
for amino acids.
• AUG codes for the
methionine and ____
of translation.
•Three codons –___, ___ and
____ do not code amino acids but
signal the termination of
translation.
2. The genetic code is __________but
not_ _________ .
• Typically several different codons
specify a given amino acid
• Any one codon indicates _
__________ amino acid.
Fig. 17.4
The genetic code (cont.)
A ______________ is established
at the translation start
RNA 5’ UUACGAUGGAUUCAAACGUCAGGGCCUAAGGCUAG3’
Met Asp Ser Asn Val Arg Ala
Stop
Start
codon
codon
Summary- The genetic code uses_ ____________________, or codons,
each of which is translated into a specific amino acid.
• 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 ____________
What actually makes the RNA?
• 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.
5’
3’
RNA
3’
5’
DNA
What marks the start of transcription??
•Answer- Specific sequences of nucleotides called the
_________ mark where gene transcription begins
•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
3’
exon
intron
exon
transcription
intron
5’
exon
into pre-mRNA
poly-A
tail
3’
cap
5’
snipped
out
snipped
out
5’
3’
mature mRNA transcript
15.3
15.2
15.1
Overview of eukaryotic transcription/translation
14
13.2
13.3
13.1
12
11
11.1
11.2
Chromosome- 1.5 x 108 base pairs containing about 3000 genes
12
13.1
13.2
13.3
14
15
21
22
23.1
23.2
23.3
31.1
31.2
31.3
0.4% of a chromosome, containing 10 genes
32
33.2 33.1
33.3
34
35.2
35.1
35.3
= exon
= intron
5’
3’
ATG B
C
+1
D
E
F
TAA
3’
5’
DNA
Transcription AAUAAA Template strand
AUG
hnRNA
Regulatory
DNA
sequences
RNA Splicing
UAA
polyA tail,cap
Transport to cytoplasm
AB
7mG
AUG
CD
E
F
AAAAAA…..
UAA
mRNA
Translation
NH2
COO-
Protein
How do proteins read the RNA molecule??
Answer-the ___________________
• _____________ (tRNA) transfers amino acids from
the cytoplasm’s pool to a
________________.
codon in mRNA
anticodon
in tRNA
amino
acid
ribosome
• The ribosome adds each
amino acid carried by tRNA
to the growing end of the
_________________
chain.
tRNA
tRNA molecule’s
attachment site
for amino acid
OH
A tRNA molecule
Fig. 17.13
• Is about ___ nucleotides long
• Contains attachment site for an
amino acid.
• Contains a loop with the
___________
The anticodon base-pairs with a
complementary codon on mRNA.
3’
5’
If the codon on mRNA is UUU, a tRNA with a
______ anticodon and a tRNA carrying phenylalanine
will bind to it.
Translation can be divided into three ______
1. initiation
2. _________
Translation
3. termination
1. Initiation
a.
Small ribosomal
subunit binds mRNA
b.
Initiator tRNA (with
methionine) is attached
to start codon
Fig. 17.17
2. Elongation - Amino acid sequentially added
Translation
c. Translocation - the ribosome
moves the tRNA with the attached
polypeptide from the A site to the P
site.
3.
Translation
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
Other translation facts
• 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
Transcription
Overview
mRNA
Mature mRNA
transcripts
Translation
rRNA
ribosomal
subunits
tRNA
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
Really bad!!
mRNA
PARENTAL DNA
amino acid sequence
ARGININE
GLYCINE
TYROSINE
TRYPTOPHAN
ASPARAGINE
ARGININE
GLYCINE
LEUCINE
LEUCINE
GLUTAMATE
altered mRNA
BASE INSERTION
altered amino acid sequence
• __________ are chemical or physical agents that
interact with DNA to cause mutations.
• ________agents include high-energy radiation like Xrays 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.
TRANSCRIPTION
Pre mRNA
Transcript
Processing
Unwinding of gene regions of a DNA molecule
mRNA
rRNA
tRNA
protein
subunits
Mature mRNA
transcripts
TRANSLATION
Synthesis of a
polypetide chain at
binding sites for
mRNA and tRNA
on the surface of
an intact ribosome
ribosomal
subunits
mature
tRNA
Convergence
of RNAs
Cytoplasmic
pools of
amino acids,
tRNAs, and
ribosomal
subunits
FINAL PROTEIN
Destined for use in
cell or for trasport
Fig. 13.14, p. 210