MCB Final Exam Lon Capa with
Discussion Questions
The figure above is a cartoon of the plus end of an individual microtubule. Based on our
discussion in lecture, which of the following statements is correct? - correct answer-The
plus end is shrinking
True or False: The two ends of a microtubule that is growing in vitro (with neither end
capped) have different critical concentrations. - correct answer-True
Which of the following is/are MAPs?
Protein(s) that bind the GTP cap and promote assembly of microtubules
Proteins that promote bending of proto-filaments and promote disassembly of
microtubules
Proteins that bind the sides of microtubules and connect to other proteins such as
intermediate filament
Protein(s) that bind the GTP cap and promote assembly of microtubules, and proteins
that bind the sides of microtubules and connect to other proteins such as intermediate
filaments
All of the above - correct answer-All of the above
True or False: As described in lecture, microtubule assembly is best described as an
equilibrium reaction rather than a steady state reaction. - correct answer-False
True or False: As discussed in lecture, there are no known motor proteins that move
along intermediate filaments. - correct answer-True
By measuring microtubule growth, you find that they grow at a rate of 3 μm/min (this
number has been altered to make the following calculation easier). At this growth rate,
approximately how many alpha/beta tubulin dimers (8 nm in length) are added to the
ends of a microtubule each second (don't forget there are 13
protofilaments/microtubule)? - correct answer-3000 nm/60 sec = 50 nm/sec x dimer/8
nm = ~6 dimers/sec to each of 13 protofilaments = 78 tubulin dimers added per second
Dynamic instability causes microtubules to grow and shrink rapidly. Consider a
microtubule that is in its shrinking phase. Why is it shrinking, and what must happen at
the end of the microtubule for it to stop shrinking and start growing? - correct answer-A
microtubule that is shrinking has more GDP than GTP. To begin growing a "GTP" cap
must be added so that it grows again.
, True or False: As discussed in lecture, microtubules that are anchored in a centrosome
are nucleated by and are extensions of the microtubules that comprise the centrioles. -
correct answer-False
True or False: As discussed in lecture, within a centrosome the two centrioles are
identical to each other. - correct answer-False, one is a mother and one is a daughter
True or False: As discussed in lecture, it takes greater than 1 full cell cycle for a
centriole to mature from being "born" (or its initial formation) until it matures into a fully
functional mother centriole. - correct answer-True, it takes longer than 1 full cell cycle
You place a centrosome in a test tube that is a square plastic box the size of a cell. You
add tubulin and GTP so that microtubules can be nucleated by the centrosome and be
assembled in vitro. You initially place the centrosome in the lower right corner of your
test tube box. Once microtubules have assembled to steady state where will your
centrosome be located? - correct answer-In the center
What experimental technique or instrumentation was used to determine kinesin step
size? - correct answer-Optical Trap
A centriole is born (formed) in S-phase of one cell cycle. When does that centriole
become fully mature and active? - correct answer-M-phase of the next cell cycle
What serves as a radial map that allows a cell to "know" where its center is and where
its edges are? What structure is at the center of that map? - correct answer-Microtubule
cytoskeleton are the radial map, the center of the map is the centrosomes
True or False: Dyneins are minus end directed motors proteins - correct answer-True
True or False: As discussed in lecture, dyneins and kinesins are part of the same
superfamily of proteins. - correct answer-False
We talked about several AAA ATPase family members and the idea that some family
members are involved in one general type of process/function; whereas, other family
members are involved in another general type of process/function. What are those two
general types of processes? - correct answer-Complex assembly and disassembly and
threading
What is the name for the general type of genes identified in Lee Hartwell primary screen
for cdc mutants? - correct answer-Essential genes
What was the general phenotype that Hartwell looked for in his secondary screen? -
correct answer-Mutants in which all the individual cells with that mutation arrested at the
same stage of the cell cycle at the non-permissive (restrictive) temperature.
Discussion Questions
The figure above is a cartoon of the plus end of an individual microtubule. Based on our
discussion in lecture, which of the following statements is correct? - correct answer-The
plus end is shrinking
True or False: The two ends of a microtubule that is growing in vitro (with neither end
capped) have different critical concentrations. - correct answer-True
Which of the following is/are MAPs?
Protein(s) that bind the GTP cap and promote assembly of microtubules
Proteins that promote bending of proto-filaments and promote disassembly of
microtubules
Proteins that bind the sides of microtubules and connect to other proteins such as
intermediate filament
Protein(s) that bind the GTP cap and promote assembly of microtubules, and proteins
that bind the sides of microtubules and connect to other proteins such as intermediate
filaments
All of the above - correct answer-All of the above
True or False: As described in lecture, microtubule assembly is best described as an
equilibrium reaction rather than a steady state reaction. - correct answer-False
True or False: As discussed in lecture, there are no known motor proteins that move
along intermediate filaments. - correct answer-True
By measuring microtubule growth, you find that they grow at a rate of 3 μm/min (this
number has been altered to make the following calculation easier). At this growth rate,
approximately how many alpha/beta tubulin dimers (8 nm in length) are added to the
ends of a microtubule each second (don't forget there are 13
protofilaments/microtubule)? - correct answer-3000 nm/60 sec = 50 nm/sec x dimer/8
nm = ~6 dimers/sec to each of 13 protofilaments = 78 tubulin dimers added per second
Dynamic instability causes microtubules to grow and shrink rapidly. Consider a
microtubule that is in its shrinking phase. Why is it shrinking, and what must happen at
the end of the microtubule for it to stop shrinking and start growing? - correct answer-A
microtubule that is shrinking has more GDP than GTP. To begin growing a "GTP" cap
must be added so that it grows again.
, True or False: As discussed in lecture, microtubules that are anchored in a centrosome
are nucleated by and are extensions of the microtubules that comprise the centrioles. -
correct answer-False
True or False: As discussed in lecture, within a centrosome the two centrioles are
identical to each other. - correct answer-False, one is a mother and one is a daughter
True or False: As discussed in lecture, it takes greater than 1 full cell cycle for a
centriole to mature from being "born" (or its initial formation) until it matures into a fully
functional mother centriole. - correct answer-True, it takes longer than 1 full cell cycle
You place a centrosome in a test tube that is a square plastic box the size of a cell. You
add tubulin and GTP so that microtubules can be nucleated by the centrosome and be
assembled in vitro. You initially place the centrosome in the lower right corner of your
test tube box. Once microtubules have assembled to steady state where will your
centrosome be located? - correct answer-In the center
What experimental technique or instrumentation was used to determine kinesin step
size? - correct answer-Optical Trap
A centriole is born (formed) in S-phase of one cell cycle. When does that centriole
become fully mature and active? - correct answer-M-phase of the next cell cycle
What serves as a radial map that allows a cell to "know" where its center is and where
its edges are? What structure is at the center of that map? - correct answer-Microtubule
cytoskeleton are the radial map, the center of the map is the centrosomes
True or False: Dyneins are minus end directed motors proteins - correct answer-True
True or False: As discussed in lecture, dyneins and kinesins are part of the same
superfamily of proteins. - correct answer-False
We talked about several AAA ATPase family members and the idea that some family
members are involved in one general type of process/function; whereas, other family
members are involved in another general type of process/function. What are those two
general types of processes? - correct answer-Complex assembly and disassembly and
threading
What is the name for the general type of genes identified in Lee Hartwell primary screen
for cdc mutants? - correct answer-Essential genes
What was the general phenotype that Hartwell looked for in his secondary screen? -
correct answer-Mutants in which all the individual cells with that mutation arrested at the
same stage of the cell cycle at the non-permissive (restrictive) temperature.
