E. coli cells were spread on an agar plate, producing 1000 colonies.  The colonies are replica plated on two agar plates containing the antibiotic kanamycin and one agar plate without antibiotics.  All of the colonies are able to grow on the agar plate without antibiotic but only 4 colonies are able to grow on each of the agar plates containing kanamycin.  You notice that the four colonies that grew on each of the kanamycin containing plates are in the exact same position.  This demonstrates

#Question id: 5673

#Unit 5. Developmental Biology

Species-specific sperm attraction has been documented in numerous species. In echinoderms, sperm are attracted toward eggs of their species by chemotaxis. Following statements are about chemoattraction-

A. In this process Sperm follows a gradient of a chemical secreted by the egg.

B. These oocytes control only the type of sperm they attract, but not the time at which they attract them.

C. Releasing the chemotactic factor only when the sea urchin egg has completed all of its meiotic divisions .

D. Releasing the chemotactic factor only when the sea urchin egg is in second metaphase of its meiotic division.

E. The mechanisms of chemotaxis differ among species and chemotactic molecules are different even in closely related species.

Which of the following statement are incorrect about this process?

#Question id: 5674

#Unit 5. Developmental Biology

Following statements are regarding to the mechanism of migration of pollen tube.

A. The embryo sac is the product of three mitotic divisions of the diploid megaspore; it comprises seven cells and eight haploid nuclei.

B. The two polar nuclei in the central cell will fuse with the second sperm nucleus and produce the endosperm that will nourish the egg. The other six cells, including the egg, contain one haploid nucleus each.

C. After compatible pollen germinates, the pollen tube grows toward the micropyle.

D. The three cells from the pollen are connected to one another at the tip of the tube, and waves of sodium ions play a key role in the growth of the tube.

Which of the following combinations are correct?

#Question id: 5675

#Unit 5. Developmental Biology

Following are the statements related to mammalian chaemotaxis:

A. During chaemotaxis, the oocyte and its accompanying cumulus cells secrete molecules that attract only uncapacitated sperm toward the egg during the last stages of sperm migration.

B. These chaemotactic compound are hormone progesterone, which is made by the cumulus cells.

C. Progesterone has been shown to bind to a receptor that activates Ca2+ channels in the cell membrane of the sperm tail, leading to sperm hyperactivity and provides directional cue.

D. Cumulus cells also secrete a substance, CRISP1, that attracts sperm and hyperactivates them through CatSper channels similar as in sea urchins.

Which of  the following statement is incorrect?

#Question id: 5676

#Unit 5. Developmental Biology

The importance of dynein can be seen in individuals with a genetic syndrome known as the Kartagener triad. which of the following statement is correct?

#Question id: 5677

#Unit 5. Developmental Biology

During acrosome reaction, after binding with the egg many sperm membrane proteins are activated. Which of the following membrane protein is not activated?

#Question id: 5678

#Unit 5. Developmental Biology

Following process and their mechanism during fertilization in mammals.

Which of the following option is correct?