Mitosis Lab & Meiosis

     Today we started off by doing a lab on the different stages of mitosis in both plant and animal cells. We observed an onion root tip cells and animal cells under a microscope and drew pictures of the cells we observed going through the various stages. First interphase - DNA replication is occurring within the nucleus but physically it looks normal. The nucleus is intact and dark surrounded by cell walls. The second phase is prophase - the nucleus dissapears. The third phase is metaphase - the chromosomes line up in the middle. The fourth phase is anaphase - spindle fibers pull the two chromatids apart which forms two daughter chromosomes. And lastly telophase - a new nuclear enveloped forms around the two and if cytokinesis occurs there will be the formation of a cell wall between the two.

     After this we practiced our knowledge by looking at pictures of cells and counting the cells in each phase. This also told us how long the cells spend in each phase. Cells spend the majority of their lives in interphase.

     The mitosis I just talked about only occurs in body cells and some gametic cells. Other cells go through Meiosis. 

     Meiosis is similar, first the cells go through interphase consisting of G1, S and G2 stages, the same as in mitosis. G1 you have mom and dad DNA. In S, DNA is replicated and you have twice as much DNA. In G2 nothing really happens. Then Prophase 1 occurs, the nucleus dissapears. Then metaphase 1 - chromosomes line up in the middle, homologous structures together. Then anaphase 1 - pulled apart by spindle fibers. Telophase 1 - forms temporary nucleus and cell wall around two new cells. Prophase 2 - nucleus disappears. Metaphase 2 - line up in middle. Anaphase 2 - pulled apart. Telophase 2 - four nuclei and cell walls are formed.

    We practiced this repeatedly and noticed that almost every time we did it, a different combination of alleles came out. These random combinations are genetics, what we learned about last unit.