In human cells, both normal metabolic activities and environmental factors such as UV light can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day
A cell that has accumulated a large amount of DNA damage, or one that no longer effectively repairs damage incurred to its DNA, can enter one of three possible states:
1. an irreversible state of dormancy, known as senescence
2. cell suicide, also known as apoptosis or programmed cell death
3. unregulated cell division, which can lead to the formation of a tumor that is cancerous
So why don't we get cancer all the time?
John W. Pepper of The University of Arizona in Tucson and his colleagues used a kind of computer model called an agent-based model to compare different modes of cellular reproduction.
The results indicate that if cells reproduce by simply making carbon-copies of themselves, the cells' descendants are more likely to accumulate mutations.
In contrast, if cellular reproduction was much more complicated, the cells' descendants had fewer mutations.
Multicellular organisms use a seemingly inefficient process to replace lost cells.
An organ such as the skin calls upon skin-specific stem cells to produce intermediate cells that in turn produce skin cells.
Although great at their job, the new skin cells are evolutionary dead ends. The cells cannot reproduce.
Losing the ability to reproduce was part of the evolutionary path single-celled organisms had to take to become multicellular...
A cell that has accumulated a large amount of DNA damage, or one that no longer effectively repairs damage incurred to its DNA, can enter one of three possible states:
1. an irreversible state of dormancy, known as senescence
2. cell suicide, also known as apoptosis or programmed cell death
3. unregulated cell division, which can lead to the formation of a tumor that is cancerous
So why don't we get cancer all the time?
John W. Pepper of The University of Arizona in Tucson and his colleagues used a kind of computer model called an agent-based model to compare different modes of cellular reproduction.
The results indicate that if cells reproduce by simply making carbon-copies of themselves, the cells' descendants are more likely to accumulate mutations.
In contrast, if cellular reproduction was much more complicated, the cells' descendants had fewer mutations.
Multicellular organisms use a seemingly inefficient process to replace lost cells.
An organ such as the skin calls upon skin-specific stem cells to produce intermediate cells that in turn produce skin cells.
Although great at their job, the new skin cells are evolutionary dead ends. The cells cannot reproduce.
Losing the ability to reproduce was part of the evolutionary path single-celled organisms had to take to become multicellular...