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Ashley Ramirez

on 22 January 2013

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Transcript of Meiosis

The Journey So basically the purpose of meiosis is to produce haploid sex cells from a diploid cell. Do you think you're ready to undergo meiosis now ? Hi , I'm Jimmy. I'm gonna undergo meiosis for the first time in a couple of weeks and I'm really scared. So I'm gonna go ask my older brother John some questions. reproduction 2 parents give 1/2 of his /her genes to the offspring Before I tell you about meiosis I should tell you what occurs before it.
So first there is oegnisis which is the creation of an ovum egg cell. Then there is spermatogenesis which is the process in which a spermaloza is created. Sexual reproduction occurs when an egg cell and sperm cell join. The process of this happening is called random fertilization. In sexual Meiosis is basically a special type of cell division that produces gametes with half as many chromosomes. The opposite process would be fertilization which is the union of the egg and sperm to restore the diploid number. This results in a zygote. Humans have somatic cells which means they have two sets of chromosomes, one set from each parent. The somatic cells have 46 chromosomes arranged in 23 pairs. The two chromosomes in each pair are referred to as being homologous chromosomes. An important exception to this is the sex chromosomes ; the X and Y chromosomes. Although these chromosomes pair up they are not the same size. All other chromosomes are called autosomes. Somatic cells have two sets of autosomes and one pair of sex chromosomes called diploid. Gametes have one chromosome from each autosome pair and one sex chromosome called haploid. By: Ashley Ramirez It's time for me to tell you the process meiosis goes through. It's actually a really long journey. the tetrads have been formed Hey John, I'm scared ....
what happens during meiosis? Oh Jimmy, you have nothing to worry
about, meiosis is not a scary process at all.
In fact just the other day I went through it.
Come over here , I'll tell you all about it. The first step is Interphase , it looks like this. During
this step the chromosomes replicates and each DNA
strand unzips into two strands while free floating bases
attach to the unzipped strands. Metaphase 1 The next step is Metaphase 1. During this process Independent assortment occurs which means that the chromosomes line up randomly on either side of the metaphase plate, this is hot genetic variation is created. Anaphase 1 The next step is prophase , the two chromosomes in each momologous pair line up next to eachother. This process is called synapsis, and the resulting homologous pair is called a tetrad.Chiasma is the point where 2 homolgous sister chromatids exchange genetic information during cross over, it occurs The Journey Begins Interphase 1 Prophase 1 During Anaphase 1 the chromosome
pairs separate. Half of the chromosomes move
toward one end of the cell, the other half to
the other side. Telophase 1 Cytokinesis In Cytokinesis the rest of the cell divides. As in mitosis, the chromosomes arrive at opposite ends
of the cell and new nuclear membranes form. Interphase 2 During Interphase 2 the chromosomes
do not duplicate. Prophase 2 The same things occur here as in Prophase 1
except for crossing over. Metaphase 2 Unlike in Metaphase 1, the fibers from
the centrioles begin to pull on each one of the
chromosomes from both directions. Anaphase 2 Unlike in Anaphase 1 the fibers pull the
chromatids apart and toward opposite ends
of the cells Telophase 2 In Telpohase 2 the chromatids arrive at either end of
the dividing cell and new nuclear membranes form. Cytokenesis (End of Meiosis 2) This is the end of meiosis , we are now left with
four daughter cells , each containing one set of chromosome. Yup, I think I am.
Thanks for everything John.
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