Smoking and lung cancer smart people only please?

We have heard a million times that smoking causes lung cancer, or exess sun causes skin cancer. So, my question is that, how exactly is cancer created in someone's body? ignoring genetic defects, how does cancer start in one's body? Thank you

In extremely general terms, damage to DNA occurs that is not repaired correctly for whatever reason. Mutations may cause certain gene products (proteins) to be made in larger or smaller amounts, or to be more enzymatically active or less active.

There are certain genes, known as oncogenes, that if they become disregulated and overexpressed or too active, can influence the cell to grow and divide even when external signals are telling it not to. On the flipside, tumor suppressors normally inhibit growth and act to stop cells from dividing when they shouldn't. If mutations occur to reduce the expression of tumor suppressor genes or mess them up so they don't work, they no longer provide this safeguard.

Once cells start dividing without the normal safeguards that make them responsive to external signals that tell them not to divide, and make them check their DNA and make sure everything is ok before they divide, things can get even more out of whack.

Cancer is nothing more that mutated growth within the body. Normally mutations occur quite frequently throughout our body when free radicals are bonded with cells but most of the time they are destroyed quickly. However if for whatever some reason these cells are not able to neutralized are they are able to multiply rapidly this is when a tumor occurs. Smoking contains a lot of carcinogen's or cancer causing materials, when you smoke and you inhale these chemicals into your system they will begin to build up thus increasing the likelihood of you getting cancer. I don't think it necessarily will result in cancer but smoking irregardless already deposits tar and causes emphysema.
One of the causes is mutation of the cells due to external influences.. in this case chemicals and toxins in the smoke. Of course, genetic disposition plays a role in this too, as certain dominant genes can cause some cells to be more sensitive to certain compounds.
It's been a while since my last bio course, but as best as I can recall, free radicals (electrons that break off unstable molecules) fly around in your body and "knock" genetic material around inside the cell. Depending on what it hits, it could be fairly harmless, or it could change a cell's code and trigger it to divide rapidly without a stopping mechanism. This is cancer.
Cancer is an improper mutation of a cell, that instead of dieing due to the mutation... multiplies uncontrollably.

Cancer IS a genetic defect by definition... the cells are geneticly defective compared to other cells in the body.

Cigarette smoke contains some "alpha emitter" radio active particles. Alpha particles are essentially harmless if they are produced outside the body... Skin stops them.
But an Aplha particle that is released in the lung can easilly damage the genetic material in the cells or your lung tissue.

sunlight has a lot of gama and photonic radiation... These can penetrate the skin surface layers (which are dead...) and can cause genetic damage in cells under the protective dead layers.

Virtually ALL cancers can be traced to either hereditary genetics... or radiation.
It's all in the genes. Radiation or chemicals mess up your DNA, and if you're unlucky you end up with enough cancer cells to be a problem.
I respectfully disagree that cancer is a mutation of a cell.

Cancer cells enable life. Without cancer cells, none of us would be here.

To understand why those cells get activated inappropriately, you'd need to understand Hierarchic Organization and the Dualistic Theory of cancer.

There are two or more chapters in my book "The Doctor Who Cures Cancer" that cover these topics.

Good luck and be well.

Kelley