In the first section of this page, you will write a daily summary of that day's class.  For example in  your chapter 2 blog, your first entry should be titled 9/3/10.  You should then write a one or two paragraph summary of that day's lecture, outlining the major points.  In the second section, you are required to add two items (link to a website, video, animation, student-created slide show, student-created PowerPoint presentation) and one journal article pertaining to a topic in this chapter.  A one-paragraph summary must accompany each item describing the main idea and how it applies to the lecture topic.  Please see the PBWorks help guide for assistance embedding video and other items directly in the page.  I will also produce a how-to video on using tables to wrap text around items and other useful tips.  Please see the syllabus for organization and grading details.

A.  Daily Blog

     We should all know by now that cell division is a very intricate process that involves a great amount of accuracy and timing. One issue that a cell has doing is that the chromosomes must be properly replicated and sorted to new daughter cells. After reading chapter 15, we should all be experts with the different phases of the eukaryotic cell cycle (pffffttt... we are already experts ;D)

     Let's first review some information about chromosomes. Eukaryotic Chromosomes occur in sets. Each of these sets are composed of several different types of chromosomes. For example, humans have one set of chromosomes that has 23 different types of chromosomes. Most eukaryotic cells contain two sets of chromosomes. Going back to the example about the human species, since there are two sets of 23 different chromosomes, one human cell has a total of 46 chromosomes (one set from mommy, and one from daddy). If an organism has two sets of chromosomes, it's diploid (2n). Most of our cells are diploid, except sperm and egg cells. Those gametes, are haploid (1n), and have just one set of chromosomes. If the organism is diploid, the members of the pair of chromosomes are called homologues. This means that there is similar, however, they are not usually identical.

     So how does cell division occur? It occurs through a series of phases.... G₁, S, G₂, and M. The end product is two daughter cells. The original diploid cell had three pairs of chromosomes (six individual chromosomes). During S phase, those chromosomes replicate to yield twelve chromatids. So by the end of mitosis is complete, the two daughter cells each have six chromosomes.

     Next topic up for discussion: mitotic cell division. During this process, a cell divided to produce two new cells (daughter cells... like we touched upon before!). This process involves meiosis and cytokinesis. Meiosis is the division of one nucleus into two nuclei. It occurs as a continum of phases known as prophase, prometaphase, metaphase, anaphase, and telophase. Prophase is when the chromosomes condense and the nuclear membrane begins disassociate. Prometaphase is phase during which the mitotic spindle is completely formed. Metaphase is the phase during which the chromosomes are lined up along the metaphase plate (a plane that is halfway between the poles). The next step, anaphase, is when the connections between the pairs of sister chromatids are broken causing them to move to opposite poles. Telephase is when the chromosomes have reached their poles and the nuclear membrane re-forms. Cytokinesis, the last phase, is where the mother cell divides into the two daughter cells. So why is this process so important? DINGDINGDING. Asexual reproduction and the maintenance of multicellularity.

     Hmm, on to the next one, on to the next one. SEXUAL REPRODUCTION! AKA Meiosis. Meiosis is the process by which haploid cells are produced from a cell that was originally diploid. So when a cell begins meiosis, it contains chromosomes that are found in homologous pairs. However, when it is completed, four haploid cells are created. Similar to mitosis, meiosis begins after the cell goes through G₁, S, and G₂ phases of the cell cycle. HOWEVER, there's two important events that occur at the start of meiosis: homologous pairs of sister chromatids associate (form a tetrad) and crossing over takes place. Crossing over is the exchange of genetic information between the homologous pairs. This causes an increase in genetic variation...yay! Meiosis is split into meiosis I and meiosis II. During meiosis I, the homologues are separated into different cells. During meiosis II, the sister chromatids are separated into different cells.

     I know we have touched based on this already, and in previous chapters as well but having variation in our chromosomes really affect the characteristics of an organism. This can be any type of variation from the number of chromosome sets to the number of individual chromosomes. Our genes (not jeans) make us UNIQUE and who we are!

B.  Useful Materials

Useful Video: 2/11/11

This video talks about meiosis! It is not just a boring animation though, its a SQUARE DANCE! An animated square dance. I personally think it is adorable AND informative. All of you should watch it, it's useful!!

Helpful Image: 2/11/11

I feel like this image pretty much sums up a huge part of Chapter 15: Mitosis and meiosis. This image provides us with the basic differences and similarities between mitosis and meiosis. It's pretty much a basic overview, but I hope it helps!