Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase (DNA gene --> mRNA)
- The Three Types of RNA
- Translation by Ribosome
Transcription
• RNA polymerase
• Enzyme that oversees synthesis of mRNA
• Unwinds DNA template
• Adds complementary RNA nucleotides on DNA
template and joins them together
• Stops when it reaches termination signal
• mRNA pulls off the DNA template, is further
processed by enzymes, and enters cytosol
Transcription: From DNA to RNA
•
In transcription,
Genetic information is transferred from DNA to RNA (an RNA molecule is
transcribed from a DNA template)
GCAAATGCTGGCCGGAATCTAGGACTGC
CGTTTACGA CCGGCCTTAGATCCTGACG
GCAAATGCTGGCCGGAATCTAGGACTGC
CGTTTACGA CCGGCCTTAGATCCTGACG
U
C
G
RNA Polymerase
Makes a complementary
copy of RNA from DNA
U
A AA
GC
Transcription
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
3 Types of RNA – Each With a Different Job
Messenger RNA (mRNA)
Carries copy of gene information
to the ribosome to make protein
anticodon
Transfer RNA
(tRNA)
CUG
=
CUG
Carries amino acids to the ribosome for
linking; identified by anticodon “sign”
Ribosomal RNA (rRNA)
Part of the structure of
the ribosome; key
component in amino
acid linking machinery
Anatomy of a Messenger RNA
Trailer
Leader
Figure 10.17
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
- The Genetic Code
How Gene Instructions are Communicated
mRNA Codon Dictionary of the Genetic Code
SECOND BASE
C
A
U
UUU
U
UUC
UUA
UUG
C
Leu
UCC
UAC
UCA
Ser
UAA
UAG
CUU
CCU
CAU
CUC
CCC
CAC
Leu
CCA
Pro
CAA
CUG
CCG
CAG
AUU
ACU
AAU
ACC
AAC
AUC
Ile
AUA
G
UAU
UCG
CUA
A
Phe
UCU
ACA
Thr
AAA
Met or
AUG Start ACG
AAG
GUU
GCU
GAU
GUC
GCC
GAC
GUA
GUG
Val
GCA
GCG
Ala
GAA
GAG
G
Tyr
UGU
UGC
U
Cys
C
Stop UGA Stop A
Stop UGG
Trp G
His
Gln
Asn
Lys
Asp
Glu
CGU
U
CGC
C
CGA
Arg
G
CGG
AGU
AGC
AGA
AGG
U
Ser
GGA
GGG
C
A
Arg
G
U
GGU
GGC
A
C
Gly
A
G
Central Dogma: DNARNAProtein
DNA template strand:
CGTTTACGACCGGCCTTAGATCCTGACG
Transcription
mRNA:
GCAAAUGCUGGCCGGAAUCUAGGACUGC
Translation
Protein:
by RNA polymerase
by ribosome
Met - Leu - Ala - Gly - Ile
Translation
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome
-The Genetic Code
-The Three Steps of Translation: Initiation, Elongation, & Termination
Simplified Diagram of a Ribosome
Transcription has 3 parts:
1. Initiation, where the ribosome assembles with
mRNA
2. Elongation, where the protein chain grows
3. Termination, where the new protein is released
Translation
Initiation
Growing amino acid
chain (polypeptide)
tRNA
E P
A
mRNA
Termination
Elongation
The Big Picture Regarding DNA->RNA -> Protein
Figure 10.10
Cell Division and Gene Expression
• The Need for Cell Reproduction
- The Nature of Chromosomes
- The Cell Cycle
- Mitosis and Cytokinesis
- Cancer Cells: Abnormal Cell Cycle
• The Expression of Genes as Proteins: DNA gene --> RNA --> Protein
- Transcription by RNA Polymerase
- The Three Types of RNA
- Translation by Ribosome