Recall that DNA is instructions for making protein.

Just as a cookbook is divided into recipes…

…DNA is divided into segments called “genes.” Cyclin

Cyclin Protein that controls the rate of the cell cycle. P R C C

In other words, cyclin controls how often a cell divides. Cyclin A Cyclin B

Skin cells divide every 24 hours. Cyclin A

Liver cells: divide every year. Cyclin B

Nerve cells NEVER divide… X Cyclin C

…which is why brain and spinal cord injuries are permanent.

Again, cells know how often to divide because cyclin protiens “tell” them what to do. Skin Cells Liver Cells Nerve Cells Every 24 hours Every year Never

So what would happen to a cell without cyclin?

Without cyclin, the cell would move through the cell cycle too fast and would divide uncontrollably.

A mass of cells, called a tumor, forms.

This condition is known as cancer.

Cancer Unregulated cell division caused by cyclin proteins not being made, or being made incorrectly. D C I

How the @(%#*% does cyclin change?

ribosome DNA Amino acids Like all proteins, cyclin is made by the cell’s ribosomes following DNA instructions. P C R D ribosome DNA Cyclin Amino acids

ribosome DNA Amino acids If the DNA changes, the cyclin could be made incorrectly, leading to cancer. D C C I C ribosome DNA Cyclin Amino acids

And how the @(%#*% does DNA change???

DNA is a molecule. Something with enough energy could break its bonds. Radiation

1. Radiation (solar, nuclear, etc.)

2. Chemicals C

Cancer caused by radiation

Skin cancer (melanoma) is caused by solar radiation.

Melanoma happens when solar radiation breaks bonds in the cyclin gene Melanoma happens when solar radiation breaks bonds in the cyclin gene. Other proteins are not affected. X Cyclin

Melanoma often affects moles, because the darker-colored cells absorb more solar radiation.

On its own, melanoma is not very dangerous, since the tumor forms on the outside of the body. Such tumors can be easily removed. Radiation

However, if left untreated, a skin tumor can metastasize. Radiation

Metastasis NEW PAGE The spread of cancer throughout the body; happens when a piece of a tumor breaks off and enters the bloodstream. S B T B

Nuclear radiation, such as that released by a nuclear explosion, has more energy that UV radiation. So it affects all cells of the body – not just the ones on the outside. Radiation

Also, the entire DNA molecule is affected by nuclear radiation – not just one gene. So, all proteins are affected. X X X Cyclin X

https://nuclearsecrecy.com/nukemap/ Exposure to nuclear radiation usually causes death before cancer develops. https://nuclearsecrecy.com/nukemap/ Radiation

Radiation sickness in Hiroshima, 1945:

Nuclear radiation affects you inside and out, so unborn babies are also affected:

Cancer caused by chemicals Radiation

Lung cancer is caused by exposure to chemicals (such as tobacco smoke). Radiation

Other chemicals, such as solvents and cleaners, can also cause lung cancer if they are inhaled. Radiation

Lung cancer happens when the cyclin gene reacts with the inhaled chemicals. X Cyclin

Tumor in dissected lung: Radiation

Lung tumors in an x-ray (metastasized): Radiation

Even if you are not exposed to radiation or chemicals, you can still get cancer.

Cancer can also be caused by random errors during DNA replication.

DNA replication: Replication Enzyme