Meiosis

For this project, I had the privilege to study the process of Meiosis by creating a stop motion video. In order to do so, I had to dig deeper to find out what Meiosis actually is. I learned that Meiosis can also be referred to as reductional division. Meiosis is the foundation of sexual reproduction. Through two stages and multiple phases, Meiosis creates four haploid cells from one diploid cell. Each haploid cell has half the amount of genetic material as the original cell, meaning that it does not have enough chromosomes to create a new organism alone. This is why two haploid cells, one from each parent, must join together in a process called fertilization to form a diploid cell with enough genetic information to create a new organism. Meiosis is similar to Mitosis, but it only occurs in germ cells. The most common type of germ cells are gametes: sperm for males and eggs for females. Meiosis serves to create genetic variation within a species. It does so with two main events: crossing over and independent assortment. Crossing over occurs during prophase 1. When the chromosomes come close enough together, there is a chance that a chromatid from one chromosome crosses over onto the other chromosome (seen below). Now, each chromosome contains part of the other, thereby increasing genetic variation.

The other way genetic variation is achieved through Meiosis is through a process called independent assortment. This occurs when the haploid cells from the male and female combine to form a diploid cell. Each parent's slightly different traits have a random chance of being in their offspring. For example, in the picture below, the offspring has a chance of having traits from the dad, mom, or a mix of traits from both. 

This genetic variation is key to the survival of a species. This is because it allows individual organisms to have certain traits that allow them to survive better, which forms the basis of natural selection and evolution. However, if just one small error occurs during Meiosis, the offspring may have significant deformities. One way Meiosis could go wrong is non-disjunction. Non-disjunction is when homologous chromosomes fail to separate into their daughter cells (seen in the picture below).

This may result in diseases such as Down syndrome, Triple-X syndrome, Klinefelter's Syndrome, and Turner's Syndrome. This is also the reason that panda bears have 42 chromosomes, while normal bears have 74. Pandas may have come into existence after a disjunction occurred during meiosis of a normal bear. The result was a odd colored bear with less chromosomes. However, this color turned out to be an advantage for Pandas because the flashy color helped them to find others to mate with and ward off dangers in their bamboo habitat. This proves that non-disjunction doesn't always result in physical ailments, but can instead aid in the process of natural selection. Sadly, now that bamboo forests are disappearing, pandas are becoming endangered because their colors are no longer an advantage to them.

The final version of our stop motion movie is below. Having had some previous knowledge of stop motion movies, this project was the most fun so far. I'm very happy with how it turned out. However, in order to improve this lesson, I would recommend giving us more time to work on our project. Doing so would allow us to make a more smooth video with more frames. It would also allow us to plan through exactly what we wanted to do, so we could avoid making silly mistakes and having to restart like my partner and I did. Other than that, this was an amazing experience and I hope Mr. Wong lets us do more projects like it!

https://www.youtube.com/watch?v=AHoBRteLK1s

Works Cited:

http://www.biology.iupui.edu/biocourses/N100/2k2humancsomaldisorders.html

E.O. wilson textbook

http://www.reddit.com/r/askscience/comments/2ommzw/how_often_are_there_genetically_identical/

Cancer Interview

      I had the privilege to interview a former breast cancer patient. She is currently 50 years old, and her cancer was diagnosed when she was 44. She first noticed that she had cancer when she noticed a pea-sized lump during a self-examination. She later confirmed it was cancer with a mammogram, ultrasound, and biopsy. She also had an MRI to ensure that the cancer had not spread. Other than the lump, she had no symptoms. Her initial reaction was terror, followed by extensive amounts of research. Her treatments included lumpectomy, bilateral mastectomy, lymph node biopsy, 6 weeks of radiation, and hormonal treatment with tamoxifen. The radiation killed leftover cells on her chest, and the tamoxifen is a systemic treatment that binds with estrogen receptors on the cancer cells which then prevents cancer cells from growing. Side effects from her tamoxifen were leg cramps and hot flashes which caused sleep disruption. She also had slight memory problems caused by the tamoxifen. Through her entire cancer ordeal, she learned to appreciate time with family and friends more, and she grew closer to those who supported her. Some misconceptions about cancer are that cancer is always curable and the idea that people must have done something wrong to get cancer. Another big misconception is that mammograms can detect all breast cancer. Her piece of advice is to check your family history and if cancer runs in the family, you need to be getting periodic MRI scans because mammograms sometimes can’t detect cancer in younger women. Also it is crucial to get exercise, eat vegetables, drink alcohol moderately if at all and avoid smoking. 

Then, I did some research. I learned that there are two main types of breast cancer:

1. Ductal carcinoma in situ (DCIS). This is the most common type of non-invasive breast cancer. The word "ductal" refers to the location that the cancer starts, the milk ducts (as seen in the picture below). "Carcinoma" refers to all types on cancer that occurs in the tissue that lines organs. "In situ" means "in its original place." This type of cancer is label "non-invasive" because it is only in the milk ducts, and hasn't begin to spread to the rest of the breast. DCIS by itself isn't life-threatening, but it has a risk of developing into an intrusive cancer, which is very life threatening. Also, DCIS patients are at higher risk of the cancer returning, which is why my interviewee opted for a mastectomy.
2. Invasive (or infiltrating) ductal carcinoma. This type of breast cancer is the overall most common and is the type that afflicted my interviewee. Again, this cancer starts in the milk ducts, but unlike non-invasive, the cancerous cells tear through the ducts and grow into the fatty tissue in the breast. From there, it can spread to other parts of the body and be possibly fatal. This is why my interviewee must take tamoxifen for 10 years after her surgery: to prevent the cancer from metastasizing in other organ tissues such as bones or liver. Some patients with more aggressive forms of cancer must also undergo chemotherapy treatments. Chemotherapy is effectually a poison that targets fast growing cells such as cancerous ones. Unfortunately, chemotherapy can have terrible side-effects that can danger the life of the patient. Fortunately, my interviewee had a cancer that was determined through an Oncotype DX test of the tumor to not require chemotherapy.

Some breast cancer is hereditary, which means it is inherited. There are genetic tests that can detect only a limited number of those hereditary types, specifically those associated with the brca I and brca 2 genes. Other than having it in your genes, there are no clear causes of breast cancer, it is mostly bad luck. It could be generated by random mutations during cell division.  The reason people get breast cancer is because of the cell cycle. All cells in the body are regulated by the cell cycle, so if something goes wrong during the cell cycle, it can cause immense damage. The breast tissue of women are extremely sensitive to cancer causing agents. During the cell cycle, a cancer causing agent inflicts damage upon the DNA, or "mutates" it. The result can be a DNA strand with missing base pairs. These missing bases can lead to cancer. Another mutation that occurs is when the cancer causing agent takes over a base, causing an incorrect pairing. As my interviewee stated, the best prevention of breast cancer is to get exercise, have a heathy diet, and avoid smoking and alcohol.

Some other interesting and alarming facts regarding epidemiology I learned about breast cancer include:

• Breast cancer is the most commonly diagnosed in women, but men are still susceptible, with 2,150 men diagnosed and 410 dead because of it each year
• Breast cancer is the 2nd biggest cause of death in women, heart disease being 1st
• Of the 220,000 women diagnosed with breast cancer each year, 40,000 will die of it

But HAVE FAITH! Deaths due to breast cancer have been slowly decreasing since 1990 due to better detections and treatments, and is expected to decrease more as technology improves.

This experience was very eye-opening to me, because I never realized how much cancer effects someone's life. I am also very thankful that my interviewee was able to discover her cancer before it was serious. Cancer, now more than ever,  acts as an enormous dissuasion for me to stay away from not only smoking, but also alcohol.


Sources:

http://www.nationalbreastcancer.org/
http://www.cancer.org/cancer/breastcancer/detailedguide/breast-cancer-breast-cancer-types
http://www.breastcancer.org/

Mitosis Blog Report

For this lab activity, we used microscopes to examine the different stages of cells. We examined two materials: whitefish blastula and onion root tips. First we located the whitefish blastula under the microscope using a 10x lens. Once we found it, we used a 40x magnification lens to zoom in closer to the individual cells.

The whitefish was full of cells in different stages of the mitosis, majority being interphase. The cell circled in green is in metaphase because the chromosomes are lined up in the center of the cell. The one circled in red is in early anaphase because the chromatids have started to move to opposite sides of the cell. The one in blue is telophase because the cell has started to pinch itself in half. I never knew how easily you could see the individual spindle fibers without a high power microscope.

Next, we moved on to onion root tips. We followed the same steps of finding it with 10x and zooming in with 40x.

Again, almost all the cells were in interphase, except a few along the side of that arrow that were in late anaphase.

For the next part of our experiment, we estimated the relative length of time that a cell spends in the different stages of cell replication. For this part, we only studied the onion root tip. We were told that the length of the cell cycle is approximately 24 hours for onion root tips. First, we counted the number of cells in each stage in two fields of view. Using that information, we calculated the percent of the total cells are in each stage, and then multiplied that number by 24 hours (1,440 mins). By doing so, we estimated the amount of time the cells spend in each phase. Our data is recored below:

Analysis: 

1. It is more accurate to call mitosis "nuclear replication," rather than "cellular divison," because the nucleus isn't dividing, it is replicating.
2. Whitefish blastula and onion root tip are selected for a study of mitosis because these cell tissue types are known to have rapid cell division rates. Also light can pass through them easily, allowing them to be viewed with a light microscope. 
3. If my observations had not been restricted to the area of the root tip that is actively dividing, my results would have had only cells in interphase, which makes me wonder if the root tip we observed are beginning to stop dividing and thus have mostly cells in interphase. 
4. Based on my data, I can infer that, starting with interphase, each stage is dramatically shorter than the previous one, except for anaphase and telophase.