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?

#Question id: 5681

#Unit 5. Developmental Biology

What is the arrangement of microtubules in sperm flagellum?

#Question id: 5682

#Unit 5. Developmental Biology

During prevention of polyspermy in sea urchin the shift from ___1___ to __2____is the result of a small influx of Na+ into the egg through newly opened sodium channels. Sperm cannot fuse with egg cell membranes that have a ___3___ resting potential, so the shift means that no more sperm can fuse to the egg.

#Question id: 5683

#Unit 5. Developmental Biology

There may be an important connection between sperm translocation and capacitation. Which of the following option is correct explanation of above statement?

#Question id: 5684

#Unit 5. Developmental Biology

Capacitated mammalian sperm can sense thermal differences as small as 0.014ºC over a millimeter and tend to migrate toward the higher temperature. This ability to sense temperature difference and preferentially swim from cooler to warmer sites is called as _____1___ found only in ______2____ sperm.

#Question id: 5685

#Unit 5. Developmental Biology

Human sperm are allowed to fertilize ova having non- functional ovastacin. The following possibilities may be of significance in the fusion of these gametes:

A.        The sperms will not fertilize ova.

B.        The sperms will bind and penetrate the zona pellucida but will not be able to fuse with ovum membrane.

C.        ZP2 will not be clipped by cortical granule protease.

D.        CD9 protein of egg membrane microvilli will not be able to interact sperm membrane proteins in the absence of ovastacin.

E.         Polyspermy may occur frequently.

Which combination of statements represent the outcome of the above event?

#Question id: 5686

#Unit 5. Developmental Biology

Following statements are regarding to double fertilization in angiosperms.

A. One sperm cell fuses with the egg cell to produce the zygote that will develop into the new embryonic plant.

B. The second sperm cell fuses with the usually binucleate central cell, giving rise to the

endosperm, the tissue that nourishes the developing embryo. This second event is not “true” fertilization in the sense of male and female gametes undergoing fusion.

C. The second sperm cell fuses with the usually binucleate central cell, giving rise to the

endosperm, the tissue that nourishes the developing embryo. This second event is “true” fertilization in the sense of male and female gametes undergoing fusion.

D. During fertilization in angiosperm, when the sperm cells are released, the egg undergoes a flux of Ca2+. Then, chemicals released from the egg appear to make the sperm competent for cell fusion.

Which of the following statements are true?