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Chapter 19
The Organization and Control of Eukaryotic Genomes
Chapter 19
The Organization and Control of Eukaryotic Genomes
Chromatin structure is
based on successive
layers of DNA packing.
Chapter 19
The Organization and Control of Eukaryotic Genomes
Chapter 19
The Organization and Control of Eukaryotic Genomes
histone:
Protein “beads” that act as a spool
for wrapping DNA
nucleosomes:
Histones, along with their associated
DNA.
Chapter 19
The Organization and Control of Eukaryotic Genomes
euchromatin:
Extended form of DNA during
interphase
heterochromatin:
Tightly packed DNA in metaphase
chromosomes.
Chapter 19
The Organization and Control of Eukaryotic Genomes
Much of the genome is noncoding
•Tandemly repetitive DNA (or
satellite DNA) is found in telomeres
and centromeres
•Interspersed repetitive DNA (Alu
elements) are found throughout the
chromosome.
Chapter 19
The Organization and Control of Eukaryotic Genomes
multigene families:
Identical or similar genes clustered
together
pseudogenes:
Very similar to real genes, but code
for nonfuctional proteins.
Chapter 19
The Organization and Control of Eukaryotic Genomes
gene amplification:
Extra copies of genes for a
temporary boost in productivity
They exist as tiny circles of DNA in
the nucleolus.
Chapter 19
The Organization and Control of Eukaryotic Genomes
transposons:
Genes that “jump” from place to
place in the genome
retrotransposons:
Transposons that use an RNA
intermediate.
Chapter 19
The Organization and Control of Eukaryotic Genomes
Immunoglobins are proteins that
recognize self vs. non-self
Immunoglobin genes are
permanently rearranged during
development
(More about this when we study the
immune system.)
Chapter 19
The Organization and Control of Eukaryotic Genomes
DNA methylation (adding -CH3
groups) is a way of shutting off
certain genes
Histone acetylation (adding -COCH3
groups) activates genes
This is how cellular differentiation
and genomic imprinting work.
Chapter 19
The Organization and Control of Eukaryotic Genomes
Gene expression can be controlled
at any step of the process:
–DNA unpacking
–Transcription
–RNA processing
–Degradation of RNA
–Translation
–Polypeptide cleavage and folding
–Degradation of protein
Chapter 19
The Organization and Control of Eukaryotic Genomes
Gene expression can be controlled
at any step of the process:
–DNA unpacking
Regulation is
–Transcription
most common
–RNA processing
at the level of
–Degradation of RNA
transcription.
–Translation
–Polypeptide cleavage and folding
–Degradation of protein
Chapter 19
The Organization and Control of Eukaryotic Genomes
control elements:
Non-coding DNA that regulates gene
expression by binding with
transcription factors
–Distal control elements (enhancers)
–Proximal control elements
–Promoter / TATA box.
Chapter 19
The Organization and Control of Eukaryotic Genomes
transcription factors:
Proteins that help position RNA
polymerase on the DNA
–Activators
–Repressors.
Chapter 19
The Organization and Control of Eukaryotic Genomes
Eukaryotes do not have operons like
the ones in bacteria, but…
…coordinately controlled genes,
scattered around the genome, share
common control elements.
Chapter 19
The Organization and Control of Eukaryotic Genomes
alternate RNA splicing:
A single primary transcript can be
turned into any one of several
different mRNA molecules
yourmyhisheranswerisyesnomaybe
Chapter 19
The Organization and Control of Eukaryotic Genomes
alternate RNA splicing:
A single primary transcript can be
turned into any one of several
different mRNA molecules
yourmyhisheranswerisyesnomaybe
My answer is maybe
Chapter 19
The Organization and Control of Eukaryotic Genomes
alternate RNA splicing:
A single primary transcript can be
turned into any one of several
different mRNA molecules
yourmyhisheranswerisyesnomaybe
My answer is maybe
His answer is no.
The Molecular Biology of Cancer
protooncogenes:
If a mutation makes them too active,
they become oncogenes
tumor-supressor genes:
If a mutation makes them inactive,
this can also cause cancer
Either kind of mutation will affect
regulation of the cell cycle.
ras is a proto-oncogene:
ras is a proto-oncogene:
growth factor
ras is a proto-oncogene:
growth factor
↓
receptor
ras is a proto-oncogene:
growth factor
↓
receptor
↓
G protein
ras
ras is a proto-oncogene:
growth factor
↓
receptor
↓
G protein
ras
↓
↓
↓
transcription factor →
ras is a proto-oncogene:
growth factor
↓
receptor
↓
G protein
ras
↓
↓
↓
transcription factor →
→
protein that
stimulates the
cell cycle
ras is a proto-oncogene:
growth factor
↓
receptor
↓
G protein
ras
↓
↓
↓
transcription factor →
Normal cell
division
→
protein that
stimulates the
cell cycle
ras is a proto-oncogene:
Mutant ras becomes an oncogene:
Normal cell
division
G protein
ras
↓↓↓↓↓↓
↓↓↓↓↓↓
↓↓↓↓↓↓
transcription factor →
→
protein that
stimulates the
cell cycle
ras is a proto-oncogene:
Mutant ras becomes an oncogene:
Normal cell
division
G protein
ras
↓↓↓↓↓↓
↓↓↓↓↓↓
↓↓↓↓↓↓
transcription factor →
→
protein that
stimulates the
cell cycle
ras is a proto-oncogene:
Mutant ras becomes an oncogene:
Normal cell
division
G protein
ras
↓↓↓↓↓↓
↓↓↓↓↓↓
↓↓↓↓↓↓
transcription factor →
→
protein that
stimulates the
cell cycle
ras is a proto-oncogene:
Mutant ras becomes an oncogene:
Uncontrolled
cell division
G protein
ras
↓↓↓↓↓↓
↓↓↓↓↓↓
↓↓↓↓↓↓
transcription factor →
→
protein that
stimulates the
cell cycle
P53 is a tumor-supressor gene:
growth inhibiting
factor
P53 is a tumor-supressor gene:
growth inhibiting
factor
↓
receptor
P53 is a tumor-supressor gene:
growth inhibiting
factor
↓
receptor
↓
G protein
P53 is a tumor-supressor gene:
growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓
transcription factor →
p53
P53 is a tumor-supressor gene:
growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓
transcription factor →
p53
protein that
→ stops the
cell cycle
Mutation in the p53 gene:
growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓
p53
transcription factor → (defective)
protein that
→ stops the
cell cycle
Mutation in the p53 gene:
growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓
p53
transcription factor → (defective)
defective protein
→ does not stop
the cell cycle
Mutation in the p53 gene:
growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓
p53
transcription factor → (defective)
defective protein
→ does not stop
the cell cycle
The Molecular Biology of Cancer
Most cancers involve multiple
mutations
•Some of these can be inherited
•This is why a predisposition to
some types of cancer runs in
families.
The Molecular Biology of Cancer
p53 is a damage control protein
•It stimulates DNA repair
•It halts cell division
•It can trigger apoptosis (cellular
suicide.)
.