Grade 10 Mitosis Exam Question (Answered) | Cell Division | Life Science | Past Exam Paper

Hello everyone, my name is Asisi Pumbililili and welcome to my YouTube channel. In today's video guys, we'll be answering this mitosis question from a previous grade 10 Life Sciences question paper. So, the diagram below shows one of the phases of mitosis. Remember guys, mitosis is a cell division process. The cell division process whereby one cell divides to form two cells. And these two cells are going to be genetically identical to each other and also to the parent cell. So, this is one cell dividing to form two genetically identical cells. The chromosome number will be the same. So, if for example, the parent cell has four chromosomes, that means each daughter cell will also have four chromosomes. Alright, so we are given a diagram which is showing one of the phases of mitosis and they are not telling us which phase it is. So, identify part A. There is part A. That is very simple. These are our spindle fibers or you can say spindle threads. So, very simple. That's your spindle fiber or you can say spindle thread. It's the same thing. Okay, then identify part B. So, here part B is pointing at this point over here. That is joining the chromatids. So, joining the chromatids is obviously the centromere. So, part B is the centromere. Alright, let us go to the next question. Give one visible reason, visible meaning what you can see from the diagram to show that the phase above is metaphase. So, from the diagram that you are given, what is it that you can see that shows you that this phase in the diagram is metaphase. So, that's easy guys because we can see that the chromosomes are in the middle of the equator. And that's basically what happens in metaphase. Remember, you have the interphase that takes place first. Then you will have the prophase. Then you will have metaphase. Then you will have anaphase. Then you will have teraphase. Metaphase is what we are having here, an M for middle. We are finding our chromosomes in the middle of the equator. Okay, so chromosomes are arranged in the middle of the equator. Okay, and remember it's chromosomes and not chromatids. So, they are arranged in the middle of the equator. Chromosomes and not chromatids. Okay, then 3, 2, 3. How many chromosomes will be found in each cell at the end of the cell division? Now, how many chromosomes are we going to find in each cell at the end of cell division? So, this takes us back to what I was explaining over here. But now, let's start over. Now, what we are seeing is that in the metaphase there is 4 chromosomes. So, that basically tells us that the parent cell had 4 chromosomes, right? The parent cell had 4 chromosomes. Now, since we are going to have 2 cells at the end of the process, that means each cell is going to also have 4 chromosomes because the chromosome number is maintained in monotosis. So, that means each cell is going to have 4 chromosomes. It's easy peasy because we are having how many chromosomes here? In our diagram there's 4. If you were given another example and let's say there were 8 chromosomes. So, if a parent cell contains 8 chromosomes, that means each cell at the end of the process will also contain 8 chromosomes. Same with mitosis that takes place in our cell. So, for us human beings, each cell consists of 46 chromosomes. So, that means when a cell in our bodies undergoes mitosis, this cell that contains 46 chromosomes, it will undergo mitosis to form 2 cells. Each of those 2 cells will also contain 46 chromosomes. The chromosome number is maintained. I hope that makes sense. Alright, then 3, 2, 4. Draw the diagram. Now, we need to draw a diagram to represent the phase that occurs after the one shown above. Now, this is 4 marks and we need to be able to get 4 marks here. So, they are asking us to draw a diagram of the phase that occurs after the one that is shown above. The phase that occurs after metaphase. Remember this one is metaphase. So, the phase that occurs after metaphase. If we were to come back here, it's actually anaphase. So, in this question they are asking us to draw a diagram representing anaphase. Now, what is important to note is that obviously the centromere is going to split and the chromatids are going to repulse to opposite poles. So, what will then happen here is that you need to make sure that you use the chromosome number that you are given. So, in our metaphase diagram we are having 4 chromosomes. We are having 4 chromosomes. So, for the next phase what is then going to take place is that from these chromosomes, the centromere which is basically combining the chromatids is going to split and then each chromatid is going to be pulled to an opposite pole. So, this chromatid will be pulled downward and this chromatid will be pulled upwards. And when you draw the chromatids being pulled to opposite poles, you need to draw them in more like a V-shaped kind of a structure to show that they are being pulled to opposite poles. Let me show you. So, first things first is for us to write the caption of the diagram. So, obviously we are going to be drawing the diagram. So, we need to indicate that the diagram is going to be the anaphase diagram. Then, we start by drawing the cell membrane. Let's see if we have the cell membrane. Remember, you won't have a nuclear membrane in this case. Alright guys, so we need to obviously start by writing the caption. The diagram that we are going to draw below is the anaphase diagram. So, you need to indicate. And remember guys, you get a mark for writing down your caption. Whether you are drawing a diagram or a table or a graph, whatever that you are asked to draw, please make sure that you include your caption. You get one mark for it. Then, we draw our cell membrane. Mine won't come out perfect guys because I'm not using a normal pen. So, that will be the cell membrane. Then, I'll indicate our centriole. Then, I'll draw my spindle fibres. I will draw four spindle fibres. Let's see if I can start over here. I will draw four spindle fibres. And the reason I'm drawing four spindle fibres is because we will be having four chromatids that are pulled to opposite poles. Four on one side. Four pulled upwards. And four pulled on the other side. You can see what's happening guys. This pen is not allowing me to draw nice and pulled chromatids. There you go. I'm trying my best. I'm not sure why they are coming out like they are hearts and stuff like that. Oh my God. Okay. But you can see guys. And make sure that when you draw your anaphase diagram, there is a space in between here to show that the chromatids are pulled to opposite poles. To show that the chromatids are pulled to opposite poles. Then, we need to label guys. Obviously, this will be the cell membrane. Cell membrane. You follow all drawing and labelling rules. You draw using your pencil. You label using your pen. There is a caption. You do not shade your diagrams, your lines. Please make sure that you use your ruler when drawing your lines. Your lines must never touch each other. Must never cross each other. They must always be parallel to each other. And preferably label your diagram on the right side. Right hand side. So, draw your diagram more to the left side of your page. So that you have space to put your labels on the right side of the diagram. I am sure I am forgetting others. Your labelling lines must not have arrows at the end. It must not have an arrow at the end. And at the beginning of the structure that you are labelling, when you are drawing your label line, it must not have a big dot. There is no label on it. So, you follow exactly what I am doing with my label lines. Then, I can also label the spindle fibers. I am not using a ruler because I do not have a ruler. But you are a learner. You have a ruler. You use a ruler. Yes, ma'am. Then, you label the chromatid. Remember? Now, it is a chromatid and not a chromosome. Then, you can also label the centroid. Alright. Let me show you how we mark those guys. There are four marks. The first mark will be for the caption. So, C, P, N, L can be the code here. C, P, N, L. C for the caption. If your caption is correct, you get a mark. P, you have drawn the correct face. You can see that this face is indicating the growing, rather. It is indicating anaphase. You get a mark. N, the correct number of chromosomes or chromatids. So, remember in our metaphase, we have four chromosomes. So, that means here, we are going to basically have four chromatids pulled to each side of the pole. So, four going up and four going down. If that is correct, you get a mark. Then, for this particular diagram, they are only giving you one mark for the label. In other diagrams, guys, you can get two marks for the label. So, it depends on how they have allocated the mark. Okay. All the best.