Procedure
1. Obtain 4 petri dishes and label them #1-#4
2. Add 10 mL of brine solution to each of the petri dishes using a large, graduated, plastic pipet.
3. Do NOT add alcohol to petri dish #1. This is your control.
4. Using a graduated pipette add 0.1 mL of alcohol to petri dish #2
5. Using a graduated pipette add 0.25mL of alcohol to petri dish #3
6. Using a graduated pipette add 0.5mL of alcohol to petri dish #4.
7. Use toothpicks to transfer the brine shrimp eggs into the petri dishes. Dab the tip of the toothpick into the solution in the petri dish to get the tip wet. Then dip the wet top into the brine shrimp eggs. A small amount of eggs will stick to the wet tip of the toothpick. Swirl the toothpick around in the petri dish to distribute the eggs. Use a new toothpick for each dish.
8. Examine a 0.1 ml sample from each of the dishes with a dissecting microscope or hand lens.
9. Count the number of Brine shrimp eggs for each of the 4 plates. Then calculate the density for each plate (# of eggs/volume) Record data in the Table 5.1 in the Lab Report.
10. You will examine each of the 4 petri dishes after 1 week.
• Complete Part A of the Lab Report.
• Use steps similar to those in Part A to test the effects of the substance of your choice on the hatching of brine shrimp.
• Create a table like the one in Part A of the Lab Report for the substance you are testing.
• Answer questions is Part C of the Lab Report about your experimental design.
• Next week we will look at amphibian development. We are also looking at amphibian development in lecture. In lecture are looking at the model genetic organism Xenopus.
• You will be given a ball of play dough that has beads stuck to one side. The ball of play dough represents a zygote. The beads represent Wnt.
• Notice the location of Wnt in the zygote above. Every cell that inherits the orange Wnt will form dorsal stuctures where the Wnt is located and ventral structures will form where there is no Wnt (the blue portion in the image above.
• Wnt is a cytoplasmic determinate that determines the future dorsal part of the embryo.
• Any cells that contain Wnt, the dorsal determinant, will become the back of future organism.
• Those that do not contain Wnt will become the ventral (belly) of the embryo.
• First let's mimic what happens during the first few normal divisions in an embryo such as a Xenopus embryo. • Use the string you are provided with to create a cleavage furrow in the embryo such that both future "blastomeres" contain dorsal determents (beads). This is represented by the red line in the image above.
• Take a picture of your groups "2 cell embryo". You will need to upload this picture in your Lab Report and answer question(s) about it.
• Now we will mimic the second division that normally occurs. Use the sting to form another cleavage furrow such that you will have 4 blastomeres, all of which contain the dorsal determents (beads). This is represented by the dark blue line in the image above.
• Take a picture of your groups "4 cell embryo". You will need to upload this picture in your Lab Report and answer question(s) about it.
• Once last division. Now make a cleavage furrow at a 90 degree angle to all of your previous cleavage furrows (this time half of the blastomeres will have dorsal determinants and half will not). This is represented by the purple line in the image above.
• Take a picture of your groups "8 cell embryo". You will need to upload this picture in your Lab Report and answer question(s) about it.
• Now lets simulate some early experiments that showed these dorsal determinants existed.
• You will use a second play dough "zygote" containing Wnt for this part. Instead of completing the normal first division that leaves 2 blastomeres that both have Wnt, create a cleavage furrow using the string that creates 2 blastomeres, one that has the dorsal determinants and one that does not (this is similar to the last of the 3 divisions you did above, the one represented by the purple line).
• Take a picture of your groups new "2 cell embryo". You will need to upload this picture in your Lab Report and answer question(s) about it.