Meiosis

    Why meiosis? Asking that question is like asking, “who am I?” Meiosis creates our identity. Many say it’s to pass on our genes. However, that is not always the case as just recreating the same genes would let us be infected by invading species faster. The function of meiosis is to both pass on our genes and give genetic diversity. Genetic diversity is a very powerful tool. WIthout it, a single invasive species can desecrate the whole population. Just like how Jedi and Sith in Star Wars are a lot more powerful than the simple clones and droids, which number by the millions and can be destroyed by a single one of the former, genetic diversity in humans lead to higher survivability, at the cost of less offspring.

    In this lab, we will be making a stop motion video of meiosis and I will be doing some research on meiosis and answer the questions.

    In meiosis, “crossing over” and “independent assortment” promote genetic variation. In crossing over, chromosomes swap their DNA in order for cells to inherit different traits from different parents. This occurs in prophase 1. In anaphase I and II, independent assortment causes different chromatids to get pulled to different sides of the cell randomly. This process is entirely random so there are 4 ways to assort in anaphase 1, and 4 ways in anaphase 2, making it 4*4 = 16 ways to independently assort the chromatids.

    Non-disjunction is when a problem occurs in meiosis and the chromosomes do not separate, causing one of the cells to have twice the amount and one of the cells to have none.This can occur in meiosis 1 and also in meiosis 2. Non-disjunction occurs because of a failure of a checkpoint. To be exact, the spindle checkpoint. This checkpoint monitors the correct formation of the spindle fibers, so if this checkpoint fails to work correctly, the spindle fibers do not work on one end, making the chromosomes get pulled all to the other side. A failure in cohesin(the glue tying the two chromatids together) would also cause non-disjunction, such as if it did not un-stick, one of the spindle fibers have to break, causing the non-disjunction.

    Pandas have 42 chromosomes. They are considered to have the same ancestor as bears, but normal bears have 74 chromosomes. Why is that? This is because the panda’s chromosome is very similar to two linked chromosomes of a bear. From this, we can deduce that the deviation in the species is because of non-disjunction, when the chromosomes do not split apart during meiosis. This can explain why the panda’s chromosome has two linked chromosomes and why the panda and the bear share a common ancestor. The panda is just a mutation(I apologize to all the pandas in the world).

    This lesson could be improved by showing two sides with egg cell and sperm cell production, and then showing the two cells combining with fertilization. And the zygote that appears afterward.

    Here is the link: https://m.youtube.com/watch?v=ipxyacE5Bso