Wednesday, November 10, 2010

Meiosis Reflection!

    This is what I learned about... Meiosis!
    • I really have come to understand the process of Meiosis and its function in sexual reproduction. Meiosis is a type of cell division that produces four cells, each with hald the number of chromosomes as the parent cell. In humans, meiosis happens in the sex organs. Every human being has 46 chromosomes, 23 pairs. 22 of those pairs are homologous, which means that they make up a matching pair. Humans inherit one homologous chromosome from their father, and one from their mother. The last pair, however, can either contain homologous chromosomes or hemizygous chromosomes. If those chromosomes are hemizygous, the sex of the human will be a male (X-Y). If they are homologous, the child will be born a female. 
    • The process of meiosis consists of a two step process, thus the two phases. The first phase is the transformation, or cell-dividing, from the tetrads made up of 2 homologous chromosomes to two seperate chromosomes. In the second phase, the seperate chromosomes divide further, while possibly exchanging genetic information, to become 4 seperate chromatids-that were originally the "sister chromatids" that made up the original chromosomes in the tetrad. 
    What I have found difficult is...
    • Sometimes, I get confused diploid and haploid. I do understand that us humans are diploid, meaning we have 46 chromosomes in each cell, because we have 23 pairs. Does that mean that haploid organisms have random chromosomes only consisting of their haploid number? For example, if an organism's haploid number was forty, does that mean they have 40 chromosomes in each cell?
    Essential Question: How do biological systems regulate?
    • The biological system of the cell goes through a variety of processes in  order to maintain a specific balance necessary for the body to be healthy. One of the processes that cells go through is the process of meiosis, which is the process of cell division where four cells are produced from the interaction of two homologous chromosomes. When these homologous chromosomes interact, they exchange genetic information in the process of "crossing over." All cells go through this process of meiosis because it is absolutely essential- without it, humans would have 92 chromosomes!


    1. Almost are human cells are dipolod. Each of these cells contain two homologous sets of chromosomes. In each cell there are only two sets of chromosomes, not 46. There are 23 pairs of chromosomes in a karyotype, with the 23rd pair being the sex chromosomes. The sex chromosomes are for the haploid cells (gamete/sex cells). The haploid cells only have a single set of chromosomes.

    2. Thanks Samantha, that helped a lot!

    3. Sahare great posts and great comments. YOu are definitely starting to peel those layers and get to a deeper understanding of these concepts. That clarification will help you as we transition to genetics in Second trimester.