Experimental technique: Tracking cytoplasmic Ca2+ distribution after a sperm enters the egg Based on what they knew about the fertilization envelope (a protective layer that forms around the egg when a sperm fuses with it), Steinhardt, Shatten, and their colleagues hypothesized that changes in the distribution of Ca2+ ions in sea urchin eggs are involved in the formation of the fertilization envelope. In sea urchin eggs (as in most eukaryotic cells) the concentration of Ca2+ ions is much higher in the endoplasmic reticulum (ER) than in the cytoplasm. To see how cytoplasmic Ca2+ concentration changes in the egg during fertilization, the researchers injected a Ca2+-specific fluorescent dye into the cytoplasm of unfertilized eggs. After adding sperm to the eggs, they observed the eggs with a fluorescence microscope. The following images show the changes in fluorescence that occurred after a single sperm entered the egg. The fluorescence of the dye increased with increasing cytoplasmic Ca2+ concentration. The green color indicates the region of the cell with the highest fluorescence at that point in time.

Sort the labeled regions of the fertilized egg above based on the status of the ER Ca2+ channels and Ca2+ pumps in that region.

Experimental technique: Tracking cytoplasmic Ca2+ distribution after a sperm enters the egg Based on what they knew about the fertilization envelope (a protective layer that forms around the egg when a sperm fuses with it), Steinhardt, Shatten, and their colleagues hypothesized that changes in the distribution of Ca2+ ions in sea urchin eggs are involved in the formation of the fertilization envelope. In sea urchin eggs (as in most eukaryotic cells) the concentration of Ca2+ ions is much higher in the endoplasmic reticulum (ER) than in the cytoplasm. To see how cytoplasmic Ca2+ concentration changes in the egg during fertilization, the researchers injected a Ca2+-specific fluorescent dye into the cytoplasm of unfertilized eggs. After adding sperm to the eggs, they observed the eggs with a fluorescence microscope. The following images show the changes in fluorescence that occurred after a single sperm entered the egg. The fluorescence of the dye increased with increasing cytoplasmic Ca2+ concentration. The green color indicates the region of the cell with the highest fluorescence at that point in time.

Sort the labeled regions of the fertilized egg above based on the status of the ER Ca2+ channels and Ca2+ pumps in that region.

Check the diagram attached.It includes the labeled region

eyitbay eyitbay · Answer 2 · 2020-04-02T17:50:23+02:00

Answer:

Generally the thickening of the fertilization envelop is aided by the level of concentration of calcium ions in the cytosol of cytoplasm.The higher the concentration of Ca+ in the cystosol the thicker the fertilisation envelope, and blockage of penetration by the sperm. This was necessary to prevent polyspermy. Naturally the Ca+ are contained in the eggs and are not due to influx from external environments.

Based on this, in this experiment:therefore:

→At stage a, the calcium channels are closed. The sperm has not penetrated yet,thus no release of calcium ion into the cytosol. At c, and f, the calcium channels begins to open to release calcium, while the calcium pumps operated slowly to release calcium .Therefore concentration of calcium is rising slowly in the cytosol. But because this is a slow process the fluorescent dye is not indicated.

→At b, e,h, the calcium channels opens.The Fluorescent green dye is well pronounced because high concentration of Ca+ is released to the cytosol to aid thickening of the fertilization envelope to prevent any other fertilization.

→At d, g, Calcium channels are closed. Thus the calcium pumps, pumped calcium ions away rapidly, with consequent drop in the Fluorescent dye.

Check attachments for images