13 Jun Prior to differentiation, basal (skin) stem cells
Question
Ten Dollar Tip for the following:
Prior to differentiation, basal (skin) stem cells:
a. can be identified biochemically, but not morphologically
b. can be identified morphologically, but not biochemically
c.. can be identified in vitro, but not in vivo
d. can not be identified at all prior to differentiation
e. only adult stem cells can be identified prior to differentiation
Polymerization of both actin and tubulin monomers have several interesting parallels. Which of the following statements are correct?
a. nucleoside triphosphate hydrolysis stabilizes their polymers
b. both classes of filaments are continually polymerizing and depolymerizing
c. only actin monomers have binding sites for GTP
d. only actin monomers are stabilized by the presence of cytoplasmic
monomer binding proteins
e. both utilize two different protein subunit (? and ?) monomers
Anaphase is believed to be triggered by:
a. increase in MPF conc. c. activation of MPF
b. degradation of cyclin d. increase in mitotic cyclin conc.
During anaphase B:
a. kinetochore microtubules shorten
b. chromatids move towards cell poles
c. polar microtubules push opposite centrosomes apart
d. astral microtubules push centrosomes from cell surface
An oncogene:
a. a gene controlling Cdk production c. normal proliferation gene
b. mutated (hyperactive) proliferative gene d. normal gene inhibiting cell growth
During Metaphase:
a. one kinetochore is attached to each centromere
b. each kinetochore attaches to single microtubule
c. each kinetochore microtubule exerts tension toward spindle pole
d. polar microtubules pull centrosomes together
In higher plants, cleavage is mediated by vesicles coalescing into a cell plate. These vesicle collect at a network termed the phragmoplast formed from:
a. residual polar microtubules d. fragmented Golgi apparatus
b. residual astral microtubules e. secretory vesicles
c. fragmented endosplasmic reticulum
Laminin:
a. triple stranded stiff fibrous protein of the extracellular matrix
b. intermediate fiber which composes the nuclear lamins
c. “Y”-shaped non-collagen adhesive protein with binding sites for collagen
heparin and cells.
d. “cross” shaped, adhesive protein formed from three long polypeptides
Most cells in culture cease growing once they attain a confluent monlayer, a phenomenon originally termed “contact inhibition”. This process is now termed density-dependent inhibition and is usually ascribed to:
a. cell competition for growth factors
b. metabolite inhibition of cell growth
c. lack of available “adhesion sites”
d. cells block further growth by releasing concentration dependent growth
inhibitors
Following fertilization of Xenopus oocytes, a rapid series of cell divisions occurs. Which of the following statements are correct for the first 24 hrs of development?
a. the cell mass doubles with each division
b. the concentration of cyclin rises prior to each mitosis
c. the concentration of MPF increases preceding each G1 phase
d. cyclicity independent of MPF concentration
e. G1 and G2 phases are longest periods of the cycle
Which of the following organelles arise independent of the eukaryotes nuclear genome by growth and fission?
a. lysosomes d. endoplasmic reticulum
b. Mitochondria e. ribosomes
c. Golgi apparatus
Which of the following occurs most immediately following the binding of ATP with the myosin cross-bridge during skeletal muscle contraction?
a. cleavage of actin from myosin d. ATP hydrolysis
b. binding of actin to myosin e. set cross-bridge to inactive (low
c. setting of cross-bridge to active affinity) state
(high-affinity) state
In both budding and fission yeast:
a. haploid organisms may conjugate
b. diploid organisms may undergo meiosis and sporulation
c. both of the above
d. neither of the above
Which binding protein forms actin intersections in gel-like network of actin filaments?
a. fimbrin d. myosin I
b. ? actinin e. myosin II
c. filamin
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