Cormiers Lectures Flashcards
What two molecules control the lac Operon?
Glucose & Galactose
Homeodomain proteins
special subclass of helix-turn-helix proteins, key regulators of animal development
(homeodomains - gene regulatory proteins contain specific structural motifs that recognize DNA sequences)
Lactose. .
increases the concentration of allolactose, which binds to the repressor protein and removes it from the DNA.
Glucose. . .
addition decreases the concentration of cAMP - then bc cAMP no longer binds to CAP, this gene activator protein dissociates from the DNA, turning off the operon
What does the first gene of the lac operon, LacZ, encode?
It encodes the enzyme beta-galactosidase, which breaks down the disaccharide lactose to galactose and glucose
How does the lac operon relate to prokaryotes and eukaryotes?
Prokaryotes (like bacteria) can either use glucose or lactose for energy requirements
Antibiotic: Rifamycin
prevents DNA synthesis, blocks initiation of RNA chains by binding to RNA polymerase
Antibiotic: Chloramphemicol
Blocks peptidyl transferase reaction on ribosomes
Antibiotic: Erythromycin
binds to the exit channel of the ribosome & thereby inhibits elongation of the peptide chain
Antibiotic: Streptomycin
prevents transition from translation initiation to chain elongation - also causes miscoding
Antibiotic: Tetracycline
Blocks binding of aminoacyl-tRNA to A site of ribosome
Acetylation of histones
Euchromatin, active transcription- adding acetylases changes the charge on histones, opens them up and aids in gene expression
–Acetylation makes chromatin more accessible to other proteins in the cell
Deacetylation of histones
heterochromatin, inactive transcription
What different structural motifs are there that recognize DNA sequences?
Helix-turn-helix, Homeodomain proteins, Zinc finger motif proteins, Leucine zipper motif, Helix-loop-helix motif
-THESE REGULATORY PROTEINS can bend or change structure of DNA, influencing gene regulation and impact of enhancers and represssors!
What’s one way that gene regulatory proteins can repress transcription?
By recruiting histone deacetylases which then deacytylate histones, causing them to become heterochomatin and tightly bound (not open for modification by proteins)
What is the significance of epigenetics?
It is heritable, reversible changes in the genome that regulate gene expression, usually causing gene silencing. There is no change in DNA structure or sequence but its important in regulating the amount of expression [Chromosome wide alterations in chromatin structure - and gene expression - can be inherited] (Example: Mammalian X-chromosome inactivation)
What do histone deacytlases do?
They cause chromatin condensation!!
What is genomic imprinting?
It is an epigenetic phenomenon by which certain genes can be expressed in a parent-of-origin-specific manner. Imprinting = silencing. Genes can be paternally or maternally imprinted but not both.
-Disregulation of imprinting - can cause angelman’s syndrome, prader willie syndrome, etc.
What chaparone protein allows HIV to be transported out of the nucleus and into the cell cytoplasm?
Rev (example of nuclear transport - all other RNAs have to be capped, tailed and spliced (fully processed) before being transported out of the cell
What are the two ways that iron is regulated in the cell?
- amount of messenger RNA
2. the amount of protein that’s translated
Topo I
- more imp in eukaryotes, fixes winding problem during DNA replication
- so topoisomerase will cut the DNA - this is a reversible nicking reaction caused by topoisomerase 1
Topo II
This pulls apart one strand of DNA into two pieces - so it basically breaks the dsDNA and pulls it apart (like the rope trick) and then it fixes the double stranded breaks [largely confined to proliferating eukaryotic cells - common target for cancer]
What does telomerase do?
It adds a short piece of DNA, a telomere, that will be lost when the cell divides and DNA is replicated – shortening of telomeres causes aging – adds six nucleotide repeating sequence to 3’ end of replicated DNA strand (ex: short telomeres - in werner’s syndrome - makes people look old in their teens)
