Question

Describe the difference between a tumor suppressor and an oncogene with respect to the actual causes of cancer.

Short answer

Tumor suppressors prevent uncontrolled cell growth. Oncogenes promote uncontrolled cell growth. Both are involved in cancer when mutated.

Step-by-step solution

Understand Tumor Suppressors

Tumor suppressor genes are genes that normally help to prevent cells from becoming cancerous. They do this by controlling cell growth and division, repairing DNA mistakes, or ensuring that cells with damaged DNA undergo apoptosis (programmed cell death). When these genes are mutated or inactivated, cells can grow uncontrollably.

Understand Oncogenes

Oncogenes are mutated forms of proto-oncogenes, which normally promote cell growth and division in a controlled manner. When proto-oncogenes mutate into oncogenes, they can become permanently activated, leading to uncontrolled cell growth and potentially cancer.

Identify Key Differences

The primary difference between tumor suppressors and oncogenes is their role in cell regulation. Tumor suppressor genes act as a brake on cell division, while oncogenes act as a gas pedal. Mutations in tumor suppressor genes result in a loss of function, whereas mutations in proto-oncogenes result in a gain of function.

Relate to Causes of Cancer

Cancer can be caused by inactivation of tumor suppressor genes, which removes the control on cell division, or activation of oncogenes, leading to excessive cell division. Both mechanisms disrupt normal cell regulation and contribute to the development of cancer.

Key concepts

Cancer Biology

Cancer biology focuses on the study of how normal cells transform into cancer cells. These transformations often arise due to changes or mutations in specific genes that control cell growth and division. Key players in this process are tumor suppressor genes and oncogenes. Understanding how these genes function and what happens when they malfunction is crucial for grasping the mechanisms behind cancer.

Cancer begins when cells in part of the body start to grow out of control. Cells usually grow, divide, and die in an orderly fashion. Cancer cells, however, continue to grow and divide when they are not supposed to. They also avoid the natural process of cell death (apoptosis), leading to tumor formation.

Tumor Suppressor Genes

Tumor suppressor genes work by keeping cell growth in check. They can halt the process of cell division, repair DNA errors, or ensure that defective cells are destroyed by apoptosis. When these genes are mutated or deactivated, their control over cell growth is lost.

This lack of regulation can lead cells to divide uncontrollably, contributing to cancer development. Examples of well-known tumor suppressor genes include TP53, which produces the p53 protein that regulates cell cycle and apoptosis, and RB1, which controls cell cycle progression.

Oncogenes

Oncogenes are mutated forms of proto-oncogenes, which are genes that normally stimulate cell division and growth in a controlled manner. When proto-oncogenes mutate into oncogenes, they can become permanently activated. This leads to uncontrollable cell proliferation, a hallmark of cancer.

An example of such a mutation is in the RAS gene, which can lead to continuous cell signaling for growth even in the absence of external signals. Proto-oncogenes function like a gas pedal for cell division, but when mutated into oncogenes, they cause the gas pedal to be stuck in the 'on' position, promoting excessive cell growth.

Cell Growth Regulation

Cell growth regulation involves a balance between cell division, growth, and death. Tumor suppressor genes and oncogenes play pivotal roles in this regulation.

Tumor suppressor genes act like brake pedals, slowing down or halting cell division when necessary. They ensure cells do not grow uncontrollably. On the other hand, proto-oncogenes (which can become oncogenes through mutations) help cells grow and divide at the right times. This balance is critical for maintaining healthy tissues and organs. When either the brakes (tumor suppressor genes) fail or the gas pedal (oncogenes) gets stuck, it disrupts normal cell growth and can lead to cancer.

DNA Mutation

DNA mutations are changes in the genetic code that can affect gene function. These mutations can be inherited or acquired over one's lifetime due to factors like radiation, chemicals, or viruses.

When mutations occur in tumor suppressor genes, they can lead to a loss of function, meaning these genes can no longer control cell growth effectively. In contrast, mutations in proto-oncogenes result in their transformation into oncogenes, leading to a gain of function and excessive cell growth.

• Mutations in tumor suppressor genes result in loss of function, removing inhibition on cell division
• Mutations in proto-oncogenes lead to oncogenes, resulting in gain of function and uncontrolled cell growth

Accumulation of such mutations disrupts cell growth regulation and may culminate in cancer.