Cell 7 Flashcards
Where is nuclear lamina located?
just deep to the inner nuclear membrane
What makes up the nuclear lamina?
3 different types of intermediate filaments referred to as lamins
What’s the function of lamins?
they are involved with disassembly and re-assembly of nuclear envelope during mitosis
What causes Progeria?
defect in nuclear lamins
What is the role of lamins in prophase of mitosis?
disassembly of nuclear enevelope, mediated by phosphorylation of the lamins making up the nuclear lamina
What is the role of lamins in telophase of mitosis?
reassembly of nuclear envelope, dephosphorylation of lamins
What is heterochromatin?
tightly coiled chromatin
What is euchromatin?
loosely coiled chromatin
Which will stain more densely, heterochromatin or euchromatin?
heterochromatin will stain more densely in a basic dye
What is the distinctive feature in a stain for papillary thyroid cancer?
Orphan Annie eye nuclei “clear eye”
What is nucleostemin?
p53 binding protein found in undifferentiated cells.
As cells become more differentiated, what happens to the level of nucleostemin?
decreases thus p53 is active and functional, and can control the cell cycle
The presence of nucleostemin in cancer cells is indicative of what?
unchecked proliferation due to the inactivation of p53
What is in pars fibrosa within the nucleolus?
heavy ribosomal RNA, proteins coming in from the cytoplasm also go here
What is in pars granulosa within the nucleolus?
maturation of ribosomal subunits and appear more granulated
What are the phases of interphase?
G1, S, G2
What occurs in G1?
restriction checkpoint before proceeding to S phase, most variable stage in terms of length
What occurs in S phase?
duplication of DNA, contains S DNA-damage checkpoint
What occurs in G2?
prepares cell for mitosis and also contains G2 DNA-damage checkpoint
When do centrioles get duplicated during the cell cycle?
end of G2
How many copies of chromosomes are in G1?
one
How many copies of chromosomes are in G2?
two (after S phase)
What are colchicine, vincritine, and vinblastine?
anti-mitotic agents that inhibit polymerization of microtubules
What is the function of taxol?
promotes polymerization and inhibits depolymerization of microtubules
What can colchicine be used for?
treat gout by inhibiting expansion of cells in areas of inflammation in the body
What cells in our body have more than one nucleus?
cardiac muscle cells are commonly tetraploidy (multi-nucleated)
What occurs in prophase?
centrioles migrating to opposite poles of the cells, chromosomes are condensed. nuclear envelope still intact
What occurs in prometaphase?
initiated when lamins are phosphorylated and start to disassemble nuclear envelope
What occurs in metaphase?
the chromosomes are aligned at the equator of the spindle. the kinetochore microtubules attach sister chromatids to opposite poles of the spindle
What occurs in anaphase?
the sister chromatids synchronously separate to form two daughter chromosomes, and each is pulled slowly toward the spindle pole it faces. the kinetochore microtubules get shorter
What cleaves the cohesion complexes between chromatids?
seperase
How is separase activated?
initiated by APC (anaphase promoting complex)
What occurs in telophase?
the two sets of daughter cells are separated and the nuclear envelope reassmebles
What occurs in cytokinesis?
the cytoplasm is divided in two by a contractile ring of actin and myosin filaments, which pinches the cell in two to create two daughter cells.
What happens when cytokinesis do not occur?
a multi-nucleated cell is made
What is the effect of cytochalasin B?
inhibits polymerization of actin microfilaments
Are telomerases present in somatic cells?
no, with each round of cell division, part of the genetic info within the telomere region is lost.
What is senescence?
the cell is no longer capable of cell division
What happens in cancer regarding telomere sequence?
cancer re-expresses telomerase and thus can divide indefinitely
What is the difference between necrosis and apoptosis?
apoptosis is more organized and is normal. necrosis is messy, the contents of the cell just bursts, spilling out acidic organelles like lysosomes
When phosphatidylserine is translocated to the external layer, it is a signal for what?
marks the cell for apoptosis
What are the two types of apoptosis?
intrinsic and extrinsic
What might an aggressive tumor do to make it less susceptible to apoptosis?
increase anti-apoptotic factors
Both intrinsic and extrinsic pathways converge to what?
activation of caspase
How does extrinsic apoptosis initiated?
receptors in the plasma membrane (ie tumor necrosis receptor factor)
How does intrinsic apoptosis initiated?
cell injury such as DNA damage, growth factor withdrawal, protein misfolding, etc
What is FasL counterattack?
some cancer cells are able to express Fas ligand. they will interact with immune cells and bind to their Fas receptors. this kills off the cells that are supposed to kill cancer cells
Explain the role of estrogen in osteoblasts
when estrogen is present, it phosphorylates a pro-apoptotic factor called Bad, which is good. after menopause when estrogen levels decrease, Bad is not being phosphorylated and this leads to osteoporosis (bone cell loss)
