#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.
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a. Rheotaxis |
i.A sensing mechanism in which, the oocyte and its accompanying cumulus cells secrete molecules that attract capacitated sperm toward the egg during the last stages of sperm migration |
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b. Chemotaxis |
ii.It is a transient event, and sperm are given a relatively brief window of competence during which they can successfully fertilize the egg. |
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c. Capacitation |
iii.it is the ability to sense temperature difference and preferentially swim from cooler to warmer sites is found only in capacitated sperm. |
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d. Thermotaxis |
iv.Sperm receive long-distance directional cues from the flow of liquid from the oviduct to the uterus and they will migrate against the direction of the flow—using CatSper calcium channels to sense calcium influx and monitor the direction of the current |
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Which of the following option is correct?
#Question id: 5679
#Unit 5. Developmental Biology
Following statements regarding to the molecular processes of capacitation.
A. The sperm cell membrane is altered by the removal of albumin by cholesterol in the female reproductive tract.
B. Particular proteins or carbohydrates on the sperm surface are lost during decapacitation.
C. The membrane potential of the sperm cell becomes more positive as potassium ions leave the sperm. This change in membrane potential may allow calcium channels to be opened and permit calcium to enter the sperm.
D. Calcium and bicarbonate ions are critical in activating cAMP production and in facilitating the membrane fusion events of the acrosome reaction.
E. As a result of cAMP formation, protein phosphorylation occurs. Once they are phosphorylated, some proteins migrate to the surface of the sperm head. One of these proteins is izumo, which is critical in sperm-egg fusion.
which one of the following combinations is correct?