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Cell Bio Lecture 2

Cell Bio Midterm 1

Describe the process of chromatin remodeling. Chromatin remodeling complexes bind to the histone core of nucleosomes and to the DNA. ATP hydrolysis changes shape of the nucleosome to loosen around the DNA for nucleosome sliding. Specific regions of DNA can be exposed and allow for protein binding.
Chromatin remodeling complexes can remove all or part of the nucleosome with the help of ______. histone chaperones
T or F: The arrangement of nucleosomes on DNA is rigid. False
Define chromatin. The combination of histones, non-histone proteins, and DNA.
Define nucleosome. A protein-DNA complex consisting of two molecules each of four histones (together a histone octomer).
Name three types of histone modification. Acetylation, methylation, phosphorylation
T or F: Acetylation, methylation, and phosphorylation are non-reversible modifications. False
_________ are responsible for recruiting different enzymes for histone modification. transcription regulator proteins
____ ultimately determines where and when chromatin-modifying enzymes will act. DNA
How do cells have a "developmental memory"? Covalent modifications on histones persist after transcription regulator proteins have disappeared.
Define epigenetic inheritance. Gene expression passed on from parent to daughter cell.
Describe the reader-writer complex. Enzymes which add or remove histones and allow chromatin to attract proteins for biological functions.
Describe general transcription factors. They help to position RNA pol at the promoter, help to pull apart the DNA strands, and release RNA pol from the promoter for elongation.
Why is transcription initiation more complex in eukaryotes? DNA in eukaryotes is packaged into nucleosomes and further into chromatin.
What do transcriptional activators do? Attract RNA pol II to the start site of transcription.
What does the mediator protein complex do? Allows activator proteins to communicate with RNA pol II.
Transcription initiation requires recruitment of _______ enzymes. chromatin-modifying
_____ sequences are discarded during RNA slicing. Introns
Describe how the ends of eukaryptic mRNAs are modified before export from the nucleus. Capping at the 5' end and polyadenylation at the 3' end.
In order to be exported out of the nucleus, mRNAs are guided through _______. nuclear pore complexes
Transcripts have a half-life determined by _______ sequence. poly-A tail
Define nonsense-mediated decay. Eliminates defective mRNAs before they move away from the nucleus.
The initiator t-RNA always carries the amino acid _______. methionine
T or F: Only a single initiation can take place on each mRNA to be translated. False
What are two ways which mRNA can regulate translation? Bind to mRNA and degrade it, bind to mRNA and prevent reading of the sequence.
Describe how nonsense-mediated decay works. If the cell finds an mRNA with a stop codon in the wrong place it will degrade the mRNA while it is being translating.
Where does the information for polypeptide chain folding come from? sequence of amino acids produced by the ribosome
Molecular _____ aid in the folding of proteins. chaperones
The apparatus that deliberately destroys misfolded proteins is the ______. proteosome
Proteosome degradation is driven by ____ hydrolysis. ATP
Describe how the proteosome destroys misfolded proteins. It converts the protein into short peptides and marks it with ubiquitin linked at lysine 48.
How are cells isolated from tissues? By disruption of the extracellular matrix (cell-cell adhesion) by introduction of proteolytic enzymes.
What method is used to isolate cell populations? Fluorescence-activated cell sorter (FACS).
How does FACS work? The machine collects cells which are positive for a fluorescent marker in one area, and negative in another area.
What is the difference between "in vitro" and "in vivo"? In vitro means "in glass" while in vivo means "in the living organism".
What is the difference between bacteria and cell cultures? Cell cultures need something to adhere to, so the dish is coated with extracellular matrix materials.
Define primary cultures. Cultures prepared directly from the tissues of an organism.
Define antibodies. Highly specific proteins which bind to counteract specific antigens.
Hybridoma cell lines allow for production of an unlimited quantity of identical _____. antibodies
Describe how hybridoma cell lines are made. B lymphocytes from immunized mouse tumor cells are fused with a differentiated normal cell line and hybridized. The resulting cells give monoclonal antibodies and can multiply indefinitely.
Define totipotent cells. Cells which can give ride to any type of cell in the body (ie. fertilized egg).
Define pluripotent cells. Cells which can give rise to most cells in the body, but not all.
Embryotic stem cells are considered ______. pluripotent
Define induced pluripotent cells (iPS). Adult cell types which are converted into ES cells by forcing different expression factors.
Can iPS and ES cells be implanted into later stage embryos? Why or why not? No, they fail to receive differentiation cues, are not properly controlled and thus lead to tumors.
Describe therapeutic cloning. The nucleus is removed from an unfertilized egg and a somatic cell nucleus is inserted. Potential cells include both adult cells and stem cells.
Describe the events involved in iPS reprogramming. Activate OSKM expression, loss of fibroblast specific marker protein, gain of embryonic marker protein, endogenous Oct4 gene switched on; not fully reprogrammed to ground state (some memory).
What are two uses for iPS cells? Use for tissue repair, finding out what therapeutics are useful for a particular disease.
Created by: goberoi



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