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

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.

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 -CH 3 groups) is a way of shutting off certain genes Histone acetylation (adding -COCH 3 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 –Transcription –RNA processing –Degradation of RNA –Translation –Polypeptide cleavage and folding –Degradation of protein Chapter 19 The 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 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. Chapter 19 The 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

G protein ras ras is a proto-oncogene:

G protein ras ras is a proto-oncogene: Mutant ras becomes an oncogene:

ras is a proto-oncogene: Mutant ras becomes an oncogene: G protein ras ↓ ↓ ↓ ↓ ↓ ↓ transcription factor

ras is a proto-oncogene: G protein ras ↓ ↓ ↓ ↓ ↓ ↓ transcription factor → Mutant ras becomes an oncogene:

ras is a proto-oncogene: 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:

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.