1/23/10

During this past week in Science we learned about Meiosis.

At the beginning of this week we decided that we needed to find the answers to certain questions in order to understand meiosis.

Another word for meiosis is Asextual reproduction. We learned about meiosis by going online and researching it. When we went to cells alive, it showed us the pictures or a stimulous of the process, and it gave a short description of what happens during each of the phases. We learned that the phases are: Diploid cell, Prophase 1, Metaphase 1, Anaphase1, Telophase 1, Prophase 2, Metaphase 2, Anaphase 2, Telophase 2, and Gamete. Also, we learned Meiosis makes four replicated cells that each have a nucleus, chromosomes, and DNA.

What Meiosis really is, is the process of cell replication for sperm and egg cells. It makes the cells so they have reduced DNA. It has two parts and makes 4 daughter cells, unlike mitosis which makes 2 daughter cells.

We should know this because it is the process that takes place in cells in our bodies.

This week we also learned about autosomes. Humans have 46 chromosomes. 23 from their mom and 23 from their dad. 44 of these chromosomes are autosomes. Autosomes are really just chromosomes. 22 are from the mom and 22 are from the dad. The other two chromosomes are sex chromosomes (1 from each parent). The mom always give and X and the dad either gives an X or a Y which decides which gender the baby is.

Homework 1/19/2010

This week in science, we learned about the cell cycle.We learned that different cells go through the cycle different amounts of times. The parts of the cycle are- Mitosis, Gap 1, Synthesis, and Gap 2.

We also learned some new vocabulary.

Chromosomes-organized DNA

Chromatids-two chromosomes or sister chromosomes that form an "x" shape

Centriols-create spindle fibbers

Chromatins-unraveled, unorganized DNA

Mitosis happens very quickly. Cells spend 50% of their time in interphase, 27% of their time in prophase, 8% of their time in metaphase, 5% of their time in anaphase, and 2% of their time in telophase. Interphase is not even part of the mitosis process and that is the stage it is in for the longest amount of time.

Many different things are going on during mitosis. During interphase the cell enlarges, the chromosomes replicate, and the centriols replicate. The next part is prophase, this is when the chromosomes condense, the nucleolus disappears, and centriols migrate to the opposite sides. Then prometaphase occurs when the nuclear envelopes, as well as other membranes disintegrate. Next is metaphase where the spindle fibers attach to chromosomes at kinetochores, and chromosomes align on metaphase plates. Now anaphase begins, this is when the spindle fibers shorten, sister chromatids are pulled apart by contracting fibers, and they then move to different poles and the poles move apart. Then telophase starts and the nuclear envelope reforms, the chromosomes disperse, and the spindle fibers dissolve. Now Interphase starts again and the cell has gone through mitosis.