Use the following information to answer the question. In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below. Treatments:

A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads

B: S. purpuratus sperm mixed with beads containing no ERB1 protein

C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads

D: S. franciscanus sperm mixed with beads containing no ERB1 protein

 What is a broader implication from the observations of the experiment?

TLS Online TPP Program

#Question id: 12481

#Unit 2. Cellular Organization

Following statements are regarding to Kinetochore-microtubule interaction in S. cerevisiae.

A. In the simple kinetochore of S. cerevisiae, a protein complex called CBF3 associates with specialized, centromere-specific form of histone H3, called CENP-A.

B. The Ndc80 complexes initially make lateral interactions with a spindle microtubule and subsequently interact with a Dam1 complex, which forms a ring around the end of the microtubule. This interaction results in an end-on attachment of the centromere to the

spindle microtubule.

C. Microtubules that “capture” kinetochores are selectively stabilized by a reduction in the rate of catastrophes, which increases the chance that the attachment will persist.

D. With the two kinetochores attached to opposite poles, the duplicated chromosome is now under tension, being pulled in both directions by the one sets of kinetochore microtubules.

Which of the following combinations is correct?

TLS Online TPP Program

#Question id: 12190

#Unit 2. Cellular Organization

CDK activity is modulated by the following proteins:

(a) cyclin, (b) CAK, (c) Wee1,  (d) p21. Following protein act as:

I. Inhibitory kinase

II. CKI Family of proteins

III. Activatory kinase

IV. Regulatory subunit

Which of the following is correct?

TLS Online TPP Program

#Question id: 12189

#Unit 2. Cellular Organization

Following statements are regarding to model for reassembly of the nuclear envelope during telophase. 

A. Extensions of the endoplasmic reticulum (ER) associate with each decondensing chromosome and then fuse with one another, forming a double membrane around the chromosome. 

B. Dephosphorylated nuclear pore subcomplexes reassemble into nuclear pores, forming individual mini-nuclei called karyomeres. 

C. The enclosed chromosome further decondenses, and subsequent fusion of the nuclear envelopes of all the karyomeres at each spindle pole forms a single nucleus containing a full set of chromosomes.

D. Phosphorylated nuclear pore subcomplexes reassemble into nuclear pores, forming individual mini-nuclei called karyomeres.

Which of the following is incorrect?

TLS Online TPP Program

#Question id: 12188

#Unit 2. Cellular Organization

The series of events by which APC/C promotes the separation of sister chromatids at anaphase.

A. all the kinetochores have attached to spindle microtubules and the spindle apparatus is properly assembled and oriented.

B. Cdc20 specificity factor associated with APC/C directs it to ubiquitinylate securin and mitotic cyclins. 

C. A protease known as separase cleaves the cohesin subunit Scc1 (Rad21), breaking the protein circles linking sister chromatids.

D. anaphase begins as poleward force exerted on the kinetochores moves the split sister chromatids toward opposite spindle poles.

E. Following securin degradation and a decrease in mitotic CDK activity.

Which of the following series is correct?

TLS Online TPP Program

#Question id: 12187

#Unit 2. Cellular Organization

How cells know whether sister kinetochores are properly attached to the mitotic spindle?

TLS Online TPP Program

#Question id: 12186

#Unit 2. Cellular Organization

In 2001, the Nobel Prize in Physiology or Medicine was awarded to three cell cycle scientists. Paul Nurse was recognized for his studies with the fission yeast S. pombe, in particular for the discovery and characterization of the wee1+ gene. What did the characterization of the wee1+ gene tell us about cell cycle control?