Title: Chapter 12 Gene Expression
1Chapter 12Gene Expression
- Unlocking the secrets of DNA
2DNA is difficult to understand, even for the cell.
- The nucleotide sequence of DNA is the blueprint
for building proteins, but the ribosomes
responsible for making proteins cannot read DNA.
3Ribonucleic Acid
- 1) Messenger RNA
- Single strand, complimentary copy of DNA created
in nucleus contains triplet codons - 2) Transfer RNA
- Cloverleaf-shaped strand that picks up amino
acids and delivers them to the ribosome contains
triplet anti-codons - 3) Ribosomal RNA
- Makes up ribosomes joins amino acids together to
create a growing protein chain
4RNA vs DNA
- RNA is single instead of double strand
- RNA has different sugar (ribose)
- RNA has uracil which takes the place of thymine
- RNA moves out of nucleus controls protein
synthesis
5Transcription the production of RNA from the DNA
code
Adenine (DNA and RNA) Cystosine (DNA and
RNA) Guanine(DNA and RNA) Thymine (DNA
only) Uracil (RNA only)
RNApolymerase
DNA
RNA
6Protein Synthesis
- 1. Transcription
- Occurs in nucleus
- DNA makes a complimentary copy in the form of
M-RNA in a process similar to replication - M-RNA moves out of nucleus and to ribosomes in
the cytoplasm
7Transcription
8Benefits of transcription
- Transcribed copies of the DNA (in the form of
RNA) are used instead of the original DNA. - In eukaryotes, DNA in the cytoplasm is degraded
but RNA is not.
9How does transcription work?
- DNA double helix must be separated at the
hydrogen bonds between nitrogen bases. - Only one DNA strand is read by RNA polymerase.
- RNA polymerase constructs an RNA polymer.
10Building RNA polymer
- DNA ? (codes for) RNA
- A ? U
- T ? A
- C ? G
- G ? C
11Click on image to play video.
12What happens to the RNA once it is created?
- In prokaryotes, the RNA is immediately
translated. - In eukaryotes, the RNA is processed.
- Introns removed
- Exons joined together
13RNA processing
- Introns (segments of useless genes) are removed,
leaving on exons (expressed genes).
14- 2. Translation
- Occurs in cytoplasm
- T-RNA delivers amino acids to ribosomes joins
complimentary anti-codons, putting amino acids in
proper order - R-RNA forms peptide bonds to join amino acids
into a protein molecule - (T-RNA returns to pick up new amino acids)
15Translation
16Translation
17Ribosomes use this decoding scheme to determine
how to build the appropriate protein.
18How does the decoding work?
- RNA AUGCGAGGGAGAUUAUAGGAC
- Ribosomes read AUG CGA GGG AGA UUA UAG
GAC. - Each 3 nucleotide word is called a codon.
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20Try to decode AUG CGA GGG AGA UUA UAG GAC.
- Met Arg Gly Arg Leu - stop
21What happens to MetArgGlyArgLeustop?
- The ribosomes create an amino acid polymer that
is folded into a protein. - The original DNA code, transcribed to RNA,
instructs the cell to make a protein for a
specific function.
22Click on image to play video.
23What happens if there is a mutation in the
original DNA?
- Point mutations change of one nucleotide
sequence - This may or may not affect the amino acid
sequence, depending upon where the mutation
occurs in the DNA sequence.
24Gene mutations
- Point mutations
- Change one nucleotide or just a few nucleotides
in a gene - Examples sickle cell anemia cystic fibrosis
- Frame-shift mutations
- The reading pattern is displaced and shifts
into new positions - Examples duchenne Muscular Dystrophy
25Frame shift mutations
- The cat and the rat ran far.
- The ca and the rat ran far.
- The caa ndt her atr anf ar.
t
r
26Click on image to play video.
27Mutations
- Disadvantages
- Abnormal, even lethal genes can be passed on to
offspring - Advantages
- New, stronger genes can be passed on to offspring
28Chromosomal mutations
A B C D E F G H
- Deletion
- Insertion
- Inversion
- Translocation
A B C D E G H
A B C D J E F G H
A B C D E G F H
A B C D E F
G H W X Y Z
29- DNA 5 A T G C C T G A A T G A 3
- 3 T A C G G A C T T A C T 5 coding
strand - mRNA A UG C C U G A A U G A codons
- tRNA U A C G G A C U U A C U anti
codons - amino
- acids Met Pro Glu stop
- protein
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32The Central Dogma theory of Biology
(DNA RNA protein cell
functions)
33Animation of translation
- Click to automatically start animation.
34Nucleus
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36Single Messenger RNA Strand
37Single Messenger RNA Strand
38tRNA
Single Messenger RNA Strand
39tRNA
Single Messenger RNA Strand
40tRNA
Single Messenger RNA Strand
41tRNA
Single Messenger RNA Strand
42tRNA
Single Messenger RNA Strand
43tRNA
Single Messenger RNA Strand
44Single Messenger RNA Strand
45Single Messenger RNA Strand
46Single Messenger RNA Strand
47Single Messenger RNA Strand
48Single Messenger RNA Strand
49Single Messenger RNA Strand
50Single Messenger RNA Strand
51Single Messenger RNA Strand
52Single Messenger RNA Strand
53tRNA
tRNA
Single Messenger RNA Strand
54tRNA
tRNA
Single Messenger RNA Strand
55tRNA
tRNA
Single Messenger RNA Strand
56tRNA
Single Messenger RNA Strand
57tRNA
Single Messenger RNA Strand
58tRNA
Single Messenger RNA Strand
59tRNA
Single Messenger RNA Strand
60tRNA
Single Messenger RNA Strand
61tRNA
Single Messenger RNA Strand
62Single Messenger RNA Strand
63Single Messenger RNA Strand
64Single Messenger RNA Strand
65Single Messenger RNA Strand
66Single Messenger RNA Strand
67Single Messenger RNA Strand
68Single Messenger RNA Strand
69Single Messenger RNA Strand
70tRNA
Single Messenger RNA Strand
71tRNA
Single Messenger RNA Strand
72tRNA
Single Messenger RNA Strand
73tRNA
Single Messenger RNA Strand
74tRNA
Single Messenger RNA Strand
75tRNA
Single Messenger RNA Strand
76tRNA
Single Messenger RNA Strand
77tRNA
Single Messenger RNA Strand
78tRNA
Single Messenger RNA Strand
79tRNA
Single Messenger RNA Strand
80tRNA
Single Messenger RNA Strand
81Single Messenger RNA Strand
82Single Messenger RNA Strand
83Single Messenger RNA Strand
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93tRNA
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106Protein Synthesis overview
107Transcription DNA codes for RNA
- RNA polymerase
- A ? U
- T ? A
- C ? G
- G ? C
108mRNA processing
- The RNA polymer made messenger RNA (mRNA)
- DNA has junk genes. These are called introns
(useless pieces of RNA made as a result of
useless DNA). - Introns are cut (spliced).
- Exons are remaining RNA nucleotides carrying the
actual DNA code. - Exons are translated.
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110Translation RNA to amino acids
- Ribosomes read codons.
- AUG start codon
- tRNA with anticodons have amino acids attached.
111Translation
Ribosomes read until the codon that indicates
STOP.
112Amino acid chain
- The amino acid chain made in translation is then
folded. - Folded proteins enzymes, pigments, etc.
- Proteins made phenotype