Tumor Suppressor Genes

Cancer is a deadly disease that affects many families today and I would bet money on the fact that everyone who reads this post probably knows someone who has some form of cancer. A large majority of cancers are caused when something called a tumor suppressor gene becomes mutated and changes the cell cycle, or the process of cell division. In its normal form, a tumor suppressor gene has the ability to regulate when cells are allowed to divide and multiply. When a cell divides, the genetic information in them, DNA, is replicated. During this replication process mistakes can be made and these mistakes are referred to as mutations. The problem of cancer occurs sometimes when there are mutations specific to the tumor suppressor gene. If this gene becomes mutated, the cell no passes mutant genetic information along to daughter cells. The daughter cells multiply exponentially and a cancer tumor forms.

Two types of tumor suppressor genes, Rb and p53, often become mutated and lead to different types of cancers. A mutation in Rb, which is located on the 13th chromosome in humans, leads to retinoblastoma, or cancer of the retina. The Rb gene is dominant so there must be two mutated alleles, or a mutated copy of Rb from both the mother and the father, in order for the cancer to persist. When a healthy, normal copy of Rb is present it interacts with the E2F protein which regulates the S phase, or the part of the cell cycle where DNA is replicated. E2F can only interact with Rb when Rb is phosphorylated, or has a phosphorus on the end of it. A mutated version of the Rb chain is not phosphorylated and can therefore not interact with the E2F protein. Retinoblastoma occurs because mutant Rb can not interact with E2F to stop the S phase of the cell cycle and cancerous cells can occur.

Mutations of another tumor suppressor, p53, causes 50% of cancers and these forms of cancers are the most aggressive and have the highest rates of fatalities. Cancers caused by p53 include bladder, breast, cervix, colon, lung, liver, prostate and skin cancers. The p53 gene is located on chromosome 17 and contains 393 amino acids. A mutation of just one amino acid leads to a loss of function of this gene. The p53 gene has the ability to stop the cell replication process when a mutated or potentially dangerous section of a copied gene is detected. After detecting this mutated section of gene the cell replication process is stopped and the p53 gene signals for cell suicide, or cell death to occur. By ending the cell division process of this specific cell, it essentially stops the growth of a cancerous tumor before it starts.

Mutations in both p53 and Rb have been attributed to the rampant growth of cancers in many patients. Tumor suppressor genes, when they are not mutated, do exactly what their name says; they suppress the growth of cancerous tumors. Another type of gene called a proto-oncogene allow a cell to continue dividing and gives it the "go" signal. When mutated, a proto-oncogene becomes and oncogene and the cell constantly divides without stopping. Therefore an oncogene and a tumor suppressor gene in a cell spells disaster because a mutated tumor suppressor gene allows mutated genetic information to persist in daughter cells and the oncogene continues cell division of cells with these mutated genes at an accelerated rate. Doctors study proto-oncogenes and tumor suppressor genes in order to better understand appropriate treatments they can give to cancer patients.

What a Fun-gi

Fungi, the dominant decomposers of most environments, are commonly looked over in most of the required classes that college students have to take. They are a huge part of the Eukaryotic lineage but because many people are mostly interested in animals and how they interact with each other and their environment, fungi are sometimes left in the dark. (No pun intended.)

These important decomposers are involved in degrading many types of material such as dead plants, living or dead woody material, dead animals, animal fecal matter, and other types of organic matter. When I say that fungi are capable of degrading living woody material it may be a new fact that you have not heard before. Some fungi are capable of degrading wood for animals that create nest in the open cavities.

Fungi are also capable of forming symbiotic relationships with plants or with algae. Lichens are a good example of a symbiotic relationship that is formed between fungi and algae. These lichens are so dependent on one another to live that if they were separated, (which is nearly impossible to do anyways) they would not be able to survive on their own. They can also form associations with plant roots and form mycorrhizae. In both of these types of association, lichens and mycorrhizae, the fungi and the algae or plant benefits from the relationship. Not only are they capable of forming good relationships, fungi also form bad relationships such as parasitism to other plants and animals.

Many food processes also use fungi for fermentation. Yeast, a type of fungi is used in many different processes such as alcohol and bread production. So not only do the fungi provide a way to decompose living or dead organic matter, it also provides services in various associations with plants and algae as well as providing food services. It has so many different uses but is still not heavily focused on in various Biology related classes. The processes that most commonly are discussed are the mycorrhizal associations and the lichens. Both of these are very important but fungi also provide many more important services that could be focused on in more depth.

Source: Fungi

Species Spotlight

Our audio project is a spotlight piece on the Golden-Winged Warbler which may be endangered in the near future.

Good for Nothing Gobies!