In this unit, we learned about cell division and cell reproduction, mostly through the process of mitosis and meiosis. Mitosis occurs whenever more cells are need and can happen in animals during regeneration or during asexual reproduction. During mitosis, the cell is able to duplicate itself and make another cell that is exactly the same, including the same DNA, genes, everything. There are 6 different phases that occurs during mitosis in order for the cell to copy itself: interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. In interphase, there are 2 different stages that happen; the G1 and S stages of interphase. In G1, that’s when the cell gets bigger and the cell starts to prep itself. Then directly after that, comes the S stage of interphase, which is when the chromosomes all make an exact copy of themselves (called sister chromatids). These sister chromatids have the exact same genes and structure. There’s another growth phase in interphase called G2 that happens, but it’s not as important. Then comes prophase, which is when the chromatin condenses and you’re actually able to see the chromosomes. In interphase, since the chromatin wasn’t very tightly packed together, you weren’t able to really see the chromosomes yet. It’s also between prophase and metaphase that the nuclear membrane disappears, which will come in handy during metaphase. So in metaphase, things called centrioles will move to the opposite ends of the cells and microtubules will come out from the centrioles and attach onto the centromeres of the chromosomes. This is able to happen because the nuclear membrane has dissolved, and the chromosomes, which were previously inside the nucleus, are now just in the cell and no longer protected by the nuclear membrane. The microtubules will eventually develop into spindle fibers. The spindle fibers tug from the opposite poles of the cell in order to get the chromosomes to line up directly down the middle of the cell. Now comes the anaphase part of mitosis. In anaphase, the chromosomes break at the centromeres, and the sister chromatids are pulled to opposite sides of the cell. In telophase, the nuclear membrane reforms around each group of one half of the sister chromatids on each side of the poles. The nucleoli will reappear and start to decondense back into chromatin. The last step is cytokinesis. In this phase, the cytoplasm should divide in 2, creating the 2 new daughter cells.
Meiosis is slightly different because instead of wanting to duplicate the cells, you want to create genetically different cells. The process is still similar to mitosis although you will end up with 4 daughter cells instead of 2. The beginning is roughly the same. It first starts with interphase, where the DNA duplicates itself. However, now we go into prophase 1, where homologous chromosomes pairs (maternal and paternal chromosomes with the same length and genes in the same place, however, there can be different alleles for each gene) come together so tightly that they might switch genes. The process keeps going, metaphase, anaphase, telophase…but instead of stopping there, then the process starts again with the 2 daughter cells at prophase 2, then goes into metaphase 2, anaphase 2, telophase 2 and this is what’s able to create the 4 daughter cells. In males, each of the 4 cells will become a sperm, however, in females, only one chosen cell will become the egg. This is important because if you remember in prophase 1, in meiosis, the homologous pairs are so tightly wrapped around each other that the genes sometimes swap. So when anaphase occurs and pulls these new sequence of genes to the different daughter cells, there’s a chance that one of the new sequence of genes in chromosomes that carries an undesirable disease has ended up in the one chosen egg.
This unit was interesting to learn about because we were able to discover a lot about ourselves and why our DNA came to be the way they are. It was also really cool to see how certain people come to have a mutation or inherited disease through looking at the DNA and their parents’ DNA. We mostly studied using the different directed reading worksheets that quizzed us on what we learned in class/the textbook but there were also a few informative videos we were able to watch that really helped us to understand what was happening in the 2 processes of cell reproduction. There have been current advances in genetic technology and scientists are currently working on a method that will allow them to be able to take a mutation in someone’s gene that causes them to have a disease and to cut out that specific gene out and replace it with a normal one. This is way more advanced than anything before because it’s actually stopping the root of the disease and not just giving the people drugs that will help combat the symptoms of the disease. The future of genetic modification is rapidly approaching with the help of advancements in technology and this will help people, especially ones with life altering diseases to live, not just survive.