BRCA: The Breast Cancer Gene

BRCA is a gene that heightens the risk for certain cancers in the body. There are different variants of the BRCA gene; BRCA 1 and BRCA 2 are the most prominent. The purpose of the gene is to repair damaged DNA, but mutations can put patients at a higher risk for cancer. These mutations are hereditary genes which makes smaller groups of people more susceptible to the gene, as there is the mixing of similar genetic pools. Getting genetic testing at 18 is a great way to assess the risks of getting BRCA-linked cancer. New ways to test involve a saliva test instead of getting blood drawn. Among people who get genetic testing for BRCA, women with the mutation are more likely to get the linked cancers than men, although many men get linked cancers from being BRCA-positive patients.

There are many cancers that BRCA mutations can create a heightened risk for cancers such as breast cancer (for both males and females), ovarian cancer, prostate cancer, fallopian tube cancer, primary peritoneal cancer, and pancreatic cancer. Some methods can reduce the risk of getting BRCA-related cancers such as surgical prevention and hormone therapy. 

Many BRCA-positive women choose to remove their breast tissue via prophylactic mastectomies and have their ovaries removed. Because of BRCA’s hereditary nature, BRCA 1 and BRCA 2 are most common in Ashkenazi Jewish populations with 2% of people, usually with a founder mutation. Norwegian, Dutch, and Icelandic populations also carry founder mutations, with different populations having different mutations. 

References:

https://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet

https://www.hopkinsmedicine.org/health/conditions-and-diseases/breast-cancer/inherited-cancer-risk-brca-mutation

https://www.nationalbreastcancer.org/what-is-brca/#:~:-text=A%20BRCA%20mutation%20occurs%20when,helping%20to%20prevent%20breast%20cancer.

Mitosis

Mitosis is the process cells undergo to divide. The reason mitosis is crucial to all organisms is because it is what causes growth and repair within cells. For example, someone gets a paper cut and over time it begins to heal and the skin comes back. That is mitosis on a small scale. The result of mitosis is two identical cells, also referred to as “daughter cells” (Britannica, T. Editors of Encyclopaedia, 2024). It is a simple crucial process of growth that all cells must go through. 

A cell spends most of its life in interphase which includes growth phases that are not mitosis. There is the G1 phase which is growth in the cell, the S stage which is DNA replication and then the G2 stage DNA coils and organelles and “equipment” needed for mitosis are prepared (Sandra Alters & Brian Alters, 2006).

After interphase, prophase begins. Prophase is the phase where all DNA is coiled and condensed into chromosomes. The DNA is condensed and packed up into chromosomes so that none of it will get lost during the process of division. It can be thought of as packing up boxes when someone is moving so that nothing will get lost in the process. During prophase, the nucleus, nucleolus, and nuclear membrane all dissolve. This happens so that the cell will be able to begin metaphase, the next stage of mitosis (Britannica, T. Editors of Encyclopaedia 2023).

 Metaphase is crucial to cell division because this phase begins the lining up of the chromosomes. In the middle of the cell, chromosomes line up to then be pulled apart during anaphase. The mitotic spindle is what is used to pull apart the chromatids (Petruzzello, 2023). The chromatids are created during the DNA replication. Chromatids consist of a short arm, a long arm, and a centromere that connects the two (Rogers, 2023).

Anaphase happens directly after metaphase. Anaphase is the stage where the chromatids split apart in the middle of the cell. The chromatids are pulled to opposite ends of the cell by the mitotic spindle. This is an important phase of mitosis because it is used to ensure the chromatids are split on to each side evenly. In addition, the cell becomes larger and starts to pinch inwards preparing for the division (Britannica, T. Editors of Encyclopaedia 2023).

Telophase is the next stage of mitosis. This stage is when the chromosomes begin to uncoil back into long strands (noodle like) of DNA. The nucleus, nucleolus, and nuclear membrane all began to reform. The chromosomes begin to uncoil inside of the nucleus so that they do not get lost in the cell. The cell also pinches inwards more and begins separation (Petruzzello, 2023). This leads up to the last stage: cytokinesis. Cytokinesis is the separation of the cell into two identical cells (Britannica, T. Editors of Encyclopaedia 2019).

Bibliography

Alters, S., & Alters, B. (2006). Chapter 12: Cell reproduction. In Biology: Understanding life (pp. 182-183). John Wiley & Sons.

Britannica, T. Editors of Encyclopaedia (2024, May 6). mitosis. Encyclopedia Britannica. https://www.britannica.com/science/mitosis

Britannica, T. Editors of Encyclopaedia (2023, March 17). prophase. Encyclopedia Britannica. https://www.britannica.com/science/prophase

Britannica, T. Editors of Encyclopaedia (2023, March 24). anaphase. Encyclopedia Britannica. https://www.britannica.com/science/anaphase

Britannica, T. Editors of Encyclopaedia (2019, October 1). cytokinesis. Encyclopedia Britannica. https://www.britannica.com/science/cytokinesis

Petruzzello, M. (2023, March 17). metaphase. Encyclopedia Britannica. 

https://www.britannica.com/science/metaphase

Petruzzello, M. (2023, March 23). telophase. Encyclopedia Britannica. https://www.britannica.com/science/telophase

Rogers, K. (2023, February 15). chromatid. Encyclopedia Britannica. https://www.britannica.com/science/chromatid

Stingray Parthenogenesis

A North Carolina aquarium is home to the most remarkable stingray in the world. An adult female stingray called Charlotte is pregnant with four pups - without a male stingray to mate with in sight. At first it appeared Charlotte had a tumor, but on the eighth of February, scientists confirmed she was pregnant. According to the scientists managing the aquarium, she has not shared a tank with a male member of her species in at least eight years. There was speculation that she mated with one of the five sharks in her tank, but experts easily refute this theory because species cannot produce hybrid offspring with a species not closely related. The immaculate conception of Charlotte is rather a result of a phenomenon known as parthenogenesis, a form of asexual reproduction during which offspring develops from unfertilized eggs without genetic contribution by a male. These kinds of pregnancies happen most often in human care.

During the process of parthenogenesis, a female egg typically fuses with another cell known as a polar body and triggers cell division and the creation of an embryo. Parthenogenesis is a form of automixis; during an alternative form of this process, an egg cell will replace, reorganize and separate, while the polar bodies act as sperm and fertilize the egg. Dr. Dan Dombrowski, chief veterinarian at the North Carolina Museum of Natural Sciences in Raleigh, calls parthenogenesis a "stress response, or a way to save genetic material." It is known to occur in some insects, fish, birds and reptiles, such as California condors, Komodo dragons and yellow-bellied water snakes. 

Finley, B. (2024, February 14). Charlotte, a stingray with no male companion, is

     pregnant in her mountain aquarium. Phys.org. Retrieved April 5, 2024, from

     https://phys.org/news/2024-02-charlotte-stingray-male-companion-pregnant.html

Izlar, R. (2024, February 20). How a Stingray Likely Got Pregnant on Her Own.

     PBS North Carolina. Retrieved April 5, 2024, from https://www.pbsnc.org/

     blogs/science/how-a-stingray-likely-got-pregnant-on-her-own/

Human Body Systems

The human body is a single structure but comprises billions of smaller structures, including systems, organs, and cells. Systems are organizations of varying numbers and kinds of organs and different types of cells arranged together to perform complex functions for the body. Homeostasis is the state of balance among all of the body systems needed for the body to survive and function correctly. The survival of the human body depends on maintaining homeostasis of its internal environment and having all of the processes in the body work together to support the individual’s well-being and life.

Each of the major systems in the body is essential to the survival of the human organism, and each serves as a critical companion to the others. The nervous and endocrine systems direct the action and function of the body. The digestive, respiratory, and circulatory systems work together to supply oxygen and blood to tissue, remove waste, and break down, utilize, and absorb nutrients. The circulatory system carries crucial nutrients to the skeletal and muscular systems. The muscle and skeletal system collectively act to move the body based on the directions from the nervous system. The skeletal system also protectively houses internal organs, such as the brain, heart, and lungs while the muscle system aids in any body movement ranging from breathing muscles to 1-millimeter muscular structures. The skeletal system also interacts with the nervous system to coordinate sensory and muscle responses. When one of these systems is not functioning properly, one is guaranteed to feel this imbalance throughout the other systems within the body. The natural history of aging is that at some point in an individual’s life, one or more of the homeostasis processes is affected, leading to more or less significant unfavorable changes and ultimately death.

References

SEER Training Modules, Intro to the Human Body. U. S. National Institutes of Health, National Cancer Institute. 11 April 2024 <https://training.seer.cancer.gov/>.

Niemchick, A. and Rogers, . Kara (2023, November 29). human body systems. Encyclopedia Britannica. https://www.britannica.com/topic/human-body-systems-2237111