Lecture Chapters 16,17,18
Chapter 16
Control of Gene Expression
I. Prokaryotes: grow/divide rapidly as possible and adjust to environment
regulate the initiation of transcription
a. they have protein binding nucleotides near the promoter that get in the way of RNA polymerase binding
b. two types:
a. blocking proteins get in the way
b. stimulating proteins facilitate binding of RNA polymerase to promoter
II. Eukaryote: maintain homeostasis in spite of environment and regulate the body environment based upon environmental changes.
**bacteria exploit environment by transcribing to adjust cell activity to environment, eukaryotes regulate body environment based upon environment
ie of bacterial repressor
tryptophan amino acid.
Made in bacteria, unless its present in environment
If present tryptophan binds
to repressor protein and the protein is able to bind to DNA promoter for the
operon gene for tryptophan. So
tryptophan genes cant be transcribed.
Ie bacterial transcriptional
activatore (some genes have poor promoter binding sites intentionally)
Catabolite activator protein (CAP) allows bacteria to use other food if glucose is low
cAMP is high when glucose is low
cAMP binds to CAP so it can bind to DNA promoter
makes it recognizable to RNA polymerase so it can be transcribed
--*lac operon:
on switch is the CAP binding
protein which turns on “other food source” before any other food source gene
on/off switch is
lac promoter if lactose is present it binds to an operator that helps lactose enzyme be produced.
I.Gene expression controls development in Fungi, plants, animals
III. Fungi:
a. Basidoimycetes and ascomycetes: reproductive cells that influence growth more than specialization
IV. Plants
a. Specialized cells that are greatly influenced by environment
V. Animals
a. Specialized cells rigidly controlled less sensitive to environment
VI. mechanisms for development in multicelluar organisms
a.
cell movement
i. cadherins (projections spanning plasma membrane)
ii. integrins(cell surface proteins) *connective tissue
iii. feel there way to their destination
b.
induction
i. when a cell switches from one path to another due to cell cell interaction.
1. ie. Animal pole/vegetal pole interaction produces cells that will become mesoderm. (animal pole = ectoderms; vegetal pole=endoderm)
a. ectoderm = epidermis, muscle, notocord
c.
determination
i. totipotent: all cells in a blastoderm (up to 8 cell stage) are capable of expressing their entire genome
ii. determination: after 8 cell stage cell-cell interactions cause cells in a certain region to be a particular type of cell
iii. determination leads to differentiation.
d.
Programmed cell death
i. Necrosis occurs in damaged cells: cells burst and release contents
ii. Apoptosis: shrivel and shrink and are reabsorbed.
VII. Aging hypothesis
a. Accumulated mutation: not founded
b. Telomere depletion: “protective caps” of TTAGGG or telomeric regions shorten after each division.
i. Hayflick limit: allows cells to divide around 50 times.
VIII. Wear and Tear
a. Accumulation of damage
IX. Gene clock
a. Hutchinson-gildford syndrome: mutations in aging genes cause aging/death by 12.
b. Werners syndrome: gene on chromosome 8 effecting helicase enzyme involved in DNA repair. Leading to inablility to suppress tumors.
I. Mutations
a. germ line cells: future reproductive cells
c. somatic cells: body cells that wont be passed down to subsequent generation
c. point mutations: involving one or more base pairs largely due to environmental factors
d. change in gene positioning
II. Cancer
a. tumor results from inability of cell cycle suppressor genes to control division
b. metastases results when cells spread throughout the body.
c. Sarcomas: originate in connective tissue
d. Carcinomas: originate in epithelial tissue
e. Carcinogens: agents that cause cancer
III. Recombination
Gene transfer: one segment of a genome/chromosome is donated to another
Reciprocol recombination: crossing over
Read section 18.3 and 19.1 in text for tomorrow.