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Chapter 19The Organization and Control of Eukaryotic Genomes
Chromatin structure is based on successive layers of DNA packing.
Chapter 19The Organization and Control of Eukaryotic Genomes
Chapter 19The Organization and Control of Eukaryotic Genomes
Chapter 19The 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 19The Organization and Control of Eukaryotic Genomes
euchromatin:
Extended form of DNA during interphase
heterochromatin:
Tightly packed DNA in metaphase chromosomes.
Chapter 19The 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.
multigene families:
Identical or similar genes clustered together
pseudogenes:
Very similar to real genes, but code for nonfuctional proteins.
Chapter 19The 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 19The 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 19The 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 19The 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 19The 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 19The 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 19The Organization and Control of Eukaryotic Genomes
Regulation is most common at the level of transcription.
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 19The Organization and Control of Eukaryotic Genomes
transcription factors:
Proteins that help position RNA polymerase on the DNA–Activators
–Repressors.
Chapter 19The 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 19The 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 19The 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 19The 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.
Chapter 19The Organization and Control of Eukaryotic Genomes
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.
The Molecular Biology of Cancer
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
↓
↓
↓ protein that
transcription factor → → stimulates the
cell cycle
ras is a proto-oncogene:
growth factor
↓
receptor
↓
G protein ras
↓
↓
↓ protein that
transcription factor → → stimulates the
cell cycle
ras is a proto-oncogene:
Normal cell division
ras is a proto-oncogene:
Normal cell division
G protein ras
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓ protein that
transcription factor → → stimulates the
cell cycle
Mutant ras becomes an oncogene:
ras is a proto-oncogene:
Normal cell division
G protein ras
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓ protein that
transcription factor → → stimulates the
cell cycle
Mutant ras becomes an oncogene:
ras is a proto-oncogene:
Normal cell division
G protein ras
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓ protein that
transcription factor → → stimulates the
cell cycle
Mutant ras becomes an oncogene:
ras is a proto-oncogene:
Uncontrolled cell division
G protein ras
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓
↓ ↓ ↓ ↓ ↓ ↓ protein that
transcription factor → → stimulates the
cell cycle
Mutant ras becomes an oncogene:
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
↓
↓
↓ p53
transcription factor →
P53 is a tumor-supressor gene:
P53 is a tumor-supressor gene: growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓ p53 protein that
transcription factor → → stops the
cell cycle
Mutation in the p53 gene: growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓ p53 protein that
transcription factor → (defective) → stops the
cell cycle
Mutation in the p53 gene: growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓ p53 defective protein
transcription factor → (defective) → does not stop
the cell cycle
Mutation in the p53 gene: growth inhibiting
factor
↓
receptor
↓
G protein
↓
↓
↓ p53 defective protein
transcription factor → (defective) → does not stop
the cell cycle
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.)
.
The Molecular Biology of Cancer
