Cancer at the Level of the Genome

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  • 0:03 Unpredictable Cellular Changes
  • 0:47 Proto-Oncogenes
  • 1:29 Mutations of Proto-Oncogenes
  • 3:21 Tumor Suppressor Genes
  • 6:06 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will delve into the genetic changes that may occur during cancer formation. You'll learn about proto-oncogenes, oncogenes, tumor suppressor genes, viral oncogenesis, p53, and more.

Unpredictable Cellular Changes

We are all a bit shocked and surprised when good people go bad. For all you know, your friendly neighbor may turn out to be a sadistic serial killer. It's happened before, and I think we're mainly shocked about the fact that it's so unpredictable and that we sometimes think that we should've known better or been in more control.

A similar, but more devastating, shock occurs when someone learns they have cancer. It's utterly surprising, and it's also quite unpredictable. This lesson will examine some of the oftentimes unpredictable things that happen at the level of a cell's genome - things that cause a good cell to go bad and become a killer cancer cell instead.


A cell has a nucleus, which is where its DNA or genome is located. The genes code for a multitude of things, such as important proteins. They also encode the way a cell might divide and when it should do so. There are a whole host of genes within a cell that encode for one or many things simultaneously. One group of these genes is called proto-oncogenes. These are normal genes that control normal cell growth. The key thing to note right away, again, is that proto-oncogenes are normal genes, good genes that control a cell's normal growth.

Proto-Oncogene Mutation

However, sometimes these proto-oncogenes go bad. This can happen any number of ways. A mutation may occur that causes the proto-oncogenes to change and begin coding for different things. These mutations may be acquired spontaneously or due to carcinogens in life. Some mutations can be inherited, however.

I like to think of these mutations as changes in computer code. If a programmer makes a good computer program, it works just fine. The program is coded for with good code that works well. But sometimes, as anyone with a PC surely knows, things just go out of whack unpredictably, akin to spontaneous mutations in code that cause a computer to malfunction and give you the blue screen of death. Other times, the code is broken to begin with, as with acquired mutations, because of poor original programming acquired from parents.

Further still, the mutations may occur as a result of outside forces, such as carcinogens, or cancer-causing agents like smoke, that end up causing mutations in proto-oncogenes. In this case, I like to think of the computer code being changed as a result of a computer virus causing everything to stop working properly. In fact, believe it or not, viruses in nature can and do cause cancer in people. This is called viral oncogenesis, or the formation of cancer as a result of viral invasion.

There are many other ways by which a proto-oncogene can go bad that are beyond the scope of this lesson, and these include gene duplications, chromosomal rearrangements, and beyond. The end result is that all of these changes lead proto-oncogenes to become oncogenes, or genes that may potentially cause cancer.

Tumor Suppressor Genes

Once something causes a proto-oncogene to become an oncogene, this new gene may cause the affected cell to grow out of control, which is one major component of what we know as cancer.

But oncogenes are not the only genes involved in cancer formation. You see, your body has many different failsafe mechanisms that try to kill off a potential cancer cell. While the cells are dividing, there are checks and balances that try to repair a mutation in a gene before the replication is complete.

If the repair of a mutation cannot occur, a cell can actually commit suicide, called apoptosis, because it knows it may turn into a cancer cell that can kill the person it is living in, and it doesn't want to do that. Further still, your own immune system, by way of cells called cytotoxic T-cells, may be able to recognize and kill cancer cells as well.

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