Week of Science.

If I could travel back in time and talk to myself about the process of meiosis, I would tell myself to remember that each cell gets 50% of the DNA. Also, that the result meiosis is four cells. Another point would be that the cells cross over. The result or meiosis are sex cells, or gametes. Examples of gametes are:

-Egg

-Sperm

-Pollen (In plants)

Lastly, cells cross over in meiosis. They would look like this open up:

The pictures on the bottom of this is meiosis itself. At the end, you can see that the cells are almost into four new ones, but not quite.

If someone had told me that the cells cross over and that each cell gets 50% or the DNA at the end, it really would have helped me. I would have realized that this makes sense because 50% is from Mom and 50% is from Dad. Each cell has 50%, so when they come together, they would make 100%.

The simulation that Mr. Finley showed us on Friday would've really helped me because it showed the similarities between Meiosis and Mitosis. This really helped because it is easier to compare something to another thing I was already quite familiar with. (Mitosis.)

Meiosis is a very interesting (but quite difficult) subject.

This Week in Science.

We started off this week with Martin Luther King Jr. Day, so we didn't have school on Monday. On Tuesday, we reviewed for our quiz we were going to have the next day. We remembered that DNA is a double helix. Each helix is one sugar backbone. We reviewed what chromatins, chromatids and and chromosomes look like. We thought back to when we learned that in Early Prophase, the spindle fibers start to form. The spindle fibers are what connect to the kineticore during Prometaphase. They straighten the chromosomes out and pull them apart towards opposite poles of the cell.

Also in Promataphase, the DNA starts winding up and the centrioles become visible. The last thing we reviewed that day was what autosomes were. Autosomes are:

Autosomes- All of the chromosomes that aren't sex chromosomes.

We then had our quiz about Mitosis.

This week we also started learning about Meiosis. Meiosis is when a cell reproduces into four new cells, which is different from Mitosis. Mitosis is when it splits into two. The phases in Meiosis are:

1. Prophase I

2. Metaphase I

3. Anaphase I

4. Telophase I

5. Prophase II

6. Metaphase II

7. Anaphase II

8. Telophase II

There are also Diploid Cell and Gamete, but these aren't a part of part of Meiosis.

Here is what happens in each phase:

Diploid- Chromosomes produce sister chromatids.

Prophase I- Dyad pairs allign to tetrads.

Metaphase I- Spindle fibers attatch to the tetrads at the kinetocore, the spindle fibers move the tetrads to the equator.

Anaphase I- Sister chromosomes move to the opposite sides of the cell.

Telophase I- A cleavage furrow forms to begin cytokinesis. They're soon going to form into daughter cells.

Prophase II- Spindle formation begins and centrosomes begin to move to the opposite sides of the cell.

Metaphase II- Spindle fibers align the chromosomes to the center.

Anaphase II- Chromatids seperate and begin moving to opposite sides.

Telophase II- Cleavage furrow forms to begin cytokinesis.

Gamete- Nuclear envelope form. Meiosis has produced four daughter cells.

In meiosis, we make sex cells which are also called gametes.

Lastly, this week we looked at autosomes and their different sizes. We learned that there are two. One is from Mom and one is from Dad. We learned that Mom's have two X chromosomes and Dad's have one Y and one X.

In karyotypes, you can tell the gender of the baby, if it has Down Syndrome and the amount of chromosomes it has.

That is what I learned in science this week.

This week, our class started learning further information about Mitosis, a subject we had just touched bases on last week in science. Mitosis is the splitting of the nucleus. We started off the week learning about the different kinds of DNA structures and the different kinds of DNA organizations.

We learned that chromatins are unravelled, unorganized DNA. It is kinds of like a ball of yarn.

Next, we learned that chromosomes are wrapped up and very organized DNA. Instead of a ball of yarn, a chromosome is like a neatly and smoothly wrapped spool of yarn, instead of a ball.

During mitosis, DNA replicates. This is when the DNA copies itself and makes double the amount of DNA. There are pre-replication chromatids, which are only one line. There are also post-replication chromatids, which look like X's. They are two of the pre-replication chromatids, connected by a cell plate.

We then learned that during a big chunk of the cell's life, it is in interphase. This phase is also named the resting phase because from the outside, it doesn't look like the cell is doing much. On the contrary, inside the nucleus, the DNA is preparing for mitosis to begin.

We also learned that centrosomes are organized cells.

We also took the following notes:

• How many times the cell goes through the lifecycle differs, depending on the type of cell and it's structure and functions.
• Interphase is part of the lifecycle.
• Most of the cell cycle is interphase.
• Mitosis is the splitting of the nucleus.
• Some scientists say that cytokenesis is part of mitosis, but others beg to differ.
• Cytokenesis is the process of the cytoplasm splitting, hence the cytokenesis.
• Synthesize-Replicate.
• Centrioles- Create the spindle fibers.

The order of phases in mitosis (if we include interphase and cytokenesis):

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

6. Cytokenesis

That is what I learned in science this week.

In the week of 1/3-1/8

Green is definitions.

Blue is bullet points.

Red is everything else.

On Monday, Tuesday part of Wednesday of this week, people in our class presented their fermentation, protein synthesis, respiration and photosynthesis projects. Therefore, I cannot elaborate on anything I learned because I unfortunately didn't take notes of these presentations, though they were very good and informative.

This week, we started learning about Reproduction. I learned that:

Reproduction- The process of fertilization.

Fertilization- The process of the egg (ova) and the sperm joining.

We also made a chart about the following subjects:

• Organism Reproduction
• Cell Reproduction
• Sex vs. Reproduction

I unfortunately cannot make a chart, but I will clearly state the facts I know about each topic:

Organism Reproduction:

• In some, there is a sperm and egg to reproduce.
• In others, they split into two.
• The ones that split in two, they make a copy of the organelle and then replicate or copy the DNA.

Cell Reproduction:

• Before splitting, the cells must double in size.

Sex vs. Reproduction.

• Sex is like a cell delivery system.
• The sperm and egg join in sex.
• In both, they don't necessarily end up with a baby popping out.
• There is 50% sperm and 50% egg.

The next day, we talked more about reproduction.

We were asked:

Why do cells reproduce?

As a class, we came up with the two answers to this question.

We said:

• They reproduce to replace old and dead skin cells.
• They reproduce because we are growing.

We also learned that in plants, the roots are always reproducing.

We then started a lab about onion root tip cells and what they look like in the stages of reproduction. We thought of the following things to look for:

• Cells get bigger (larger cells)
• More DNA (bigger nucleus to get ready to accomadate for a new cell)
• More clumps of DNA (chromosomes.)
• More organelles.
• Splitting cells.

http://www.microscopy-uk.org.uk/micropolitan/botany/onion_root_mitosis.jpg

To see a picture of an onion root tip, click on the link above.

We drew pictures of the different looking onion root tips and what stages of reproduction we thought they were in.

For homework that night, we had to look up mitosis. Mitosis is:

Mitosis- When the nucleus divides into two nuclei and is part of a larger life cycle of life. It is in Eukaryotic cells. The Prokaryotic cell term for mitosis is Bianary Fission. The result is two identical cells.

On Friday, we looked at a stimulation and took notes about it, and we looked again at an onion root tip under a microscope.

I found notes about the following stages:

Interphase- When the DNA replicates and the centrioles divide.

Prophase- The first stage in mitosis (see above) when the nuclear envelope breaks down and strands of DNA form into chromosomes.

Prometaphase- When the nuclear envelope breaks down so there is no more recognizable nucleus.

Metaphase- Tension applied to the spindle fibers aligns and all of the chromosomes in one plane at the center of the cell.

Anaphase- When the spindle fibers shorten and the chromosomes are pulled apart.

Telophase- When the chromosomes reach the opposite poles of the dividing cell and the nuclei daughter cells form.

That is what I learned in science this week.