Control in Division amp Development pp 217228 Prokaryotes 1965 Nobel Prize to Jacob amp Monod for work on lac operon in E coli Lactose is metabolized by 3 enzymes in E coli Genes for these proteins are sequential ID: 656472
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Slide1
Chapter 11: Gene Expression
Control in Division & Development
pp 217-228Slide2
Prokaryotes
1965 Nobel Prize to Jacob & Monod for work on
lac
operon in
E. coli
Lactose is metabolized by 3 enzymes in
E. coli
Genes for these proteins are sequential
An operator sits between promoter & these structural genes
lac
operon = promoter + operator + 3 genes
Upstream regulatory gene codes for repressorSlide3
lac
operon
http://www.phschool.com/science/biology_place/biocoach/lacoperon/regulate.htmlSlide4
How it works.
Regulatory gene codes for repressor protein
Repressor protein binds to the operator site
Repressor prevents RNA polymerase advancement from its promoter site
Repressor protein selectively binds lactose & cannot bind the operator site then
Repression is lifted
genes are “turned on” only when lactose is presentSlide5
Eukaryotic control
Control is at level of individual chromosome
Euchromatin, uncoiled DNA, is site of active transcription
DNA contains bases that code for proteins (exons) & bases that do not (introns)
Exons & introns are both transcribed
Only exons are translated
Introns may serve as regulatory elementsSlide6
Transcriptional Control
Pre-mRNA is full copy of DNA gene’s message
Splicesomes
(RNA + protein) cut out introns & fuse exons;
ribozymes
(RNA) also splice
Introns regulate RNA, bind to &/ or control expression
Exons can code for functional domains
Exons can be selected to form specific proteinSlide7
Transcriptional Control
Transcription factors (TF) bind to regulatory elements on DNA, proteins, & other TF
Promoters
Enhancers
Repressors
TF recruit RNA polymerase to promoter
TF-to-TF binding can change shape of DNASlide8
TF-binding InteractionsSlide9
Genes for Development
Cells differentiate to become specialized
Every zygote has all the DNA
Cells/ tissue specialize in
morphogenesis
Cells only express DNA for their functions
Homeotic genes dictate loci of anatomy
Specific sequence within gene = “homeobox”
Homeotic genes form regulatory proteins
Control which genes are expressed
Control rates of cell division & gene expressionSlide10
Cancer & Cell Control
Proto-oncogenes control normal cell division, growth, & behavior
Carcinogen = mutagen
DNA damage
Mutated proto-oncogenes
“oncogene”
Oncogenes promote uncontrolled growth tumors (benign or malignant) cancer
Metastasis = spread of CA beyond origin
Mutated tumor-suppressor genes cancer
Mutations in all 3 tumor-suppressor genes
+
viral oncogene
+
mutated proto-oncogeneSlide11
Types of Cancer
Carcinomas
Skin & tissues lining organs
Sarcomas
Bone & muscle
Lymphomas
Lymphatic system’s solid tumors
Leukemia
Blood-forming tissues
uncontrolled WBC production