 Cancer is a deadly disease. A bunch of cells essentially lose all their sense of function and purpose and multiply in swarms until they form these life-threatening tumors. Now the question begs is that what makes these cells go so crazy in the first place? What is responsible for their weird transformation? We know that there are mutations involved but then again why mutate at all? That's what we're going to find out in this video. Something that causes cancer is called a carcinogen and these carcinogens can be a lot of different things. It can be the sun rays or some kind of chemical that you find in your surroundings or some toxins produced by some weird fungi and even viruses for that matter. So we're working with a really diverse range over here. Now the job of every carcinogen is the same. It is to damage DNA and mutate different genes. But which genes exactly? Studies have confirmed that there are three different types of genes which when mutated can result in cancer. These are the oncogenes, the tumor suppressor genes and the DNA repair genes. Oncogenes literally mean cancer causing genes and we have a dormant version of these genes inside of us called the proto-oncogenes. Now these proto-oncogenes, they regulate cell growth and division. So when they get mutated or activated, then they turn into these oncogenes. Now the thing about oncogenes is that they ruin the controlled growth of cells. So the cells now tend to multiply forever. Think of it as a stuck accelerator of a car. So it only speeds up, it continues to speed up and never slows down. Another type of genes which are involved in cancer are the tumor suppressor genes. Now these genes are more protective in nature and they counter the oncogenes. So they limit uncontrolled growth of cells and also promotes cell death to maintain the proper balance of cells. So if these cells, they lose their function or a.k.a. they get mutated, then the cells will multiply like crazy. So you can think of these mutated genes as the defective breaks of a car. So you just cannot stop the car anymore. Now the last but not least are the DNA-repared genes. Now these genes are like a failsafe. If any of the oncogenes or the tumor suppressor genes they get mutated, then these repaired genes can go ahead and fix them, unless they themselves are mutated or they get mutated and stop working. If a carcinogen goes ahead and manages to mutate any of these three types of genes, then there's a really high chance of developing cancer. Now the question is, is that how are these carcinogens going to achieve something like that? Let's quickly make some space here for our carcinogens. Now any kind of high energy radiation like the UV rays from the sun or the x-rays from the x-ray machines, even the gamma rays from the radioactive stuff, all of these rays or radiation are physical carcinogens. Now high energy, what do I mean by high energy? It means that all of those radiations on the electromagnetic spectrum which have shorter wavelength than visible light. So that includes the UV rays, the gamma rays and the x-rays. These rays directly damage the DNA by distorting the structure of the DNA molecule. But how is it doing that? Well high energy radiation, it's also called ionizing radiation, now it has the ability to weaken and break chemical bonds. So the bonds which are holding the DNA molecule together, they fall apart. So much so that the DNA strands they end up cross linking or breaking completely. And that's not all. We have these super reactive oxygen molecules inside of us. These rays induces these oxygen molecules to go ahead and react with the proteins and enzymes of the DNA replication system, effectively ruining all of the processes. Now if all of this damage is happening to any of these cancer genes over here, then they will mutate and boom cancer. Other than radiation there are some chemical compounds which are also strong contenders for carcinogens. These compounds they either directly damage the DNA by reacting with the bases and the phosphodiester backbone or they transform into carcinogenic compounds with the help of our metabolic compounds and damage the DNA. For example, mycotoxins or the toxins which are produced by fungi. Now when we ingest these toxins or they go inside of us, then they will get activated by the cytochromes which are present inside of us. And then these mycotoxins they will transform into the carcinogenic compounds which will go ahead and mess with the guanine bases of our DNA. Again to cause cancer, all of this mutation and all of this damage needs to happen to one of the cancer genes that we spoke about earlier. The more common and well known chemical compounds which can cause cancer are nicotine which is found in cigarettes and asbestos which is found which is pretty common in certain industries. Both of these compounds cause severe cases of lung cancer. There is another type of carcinogen which is rather peculiar in nature. Biological carcinogens aka viruses. Certain kinds of viruses called oncogenic viruses can cause cancer with the help of their own set of oncogenes. They either insert these viral oncogenes into our cell and wreak havoc or they activate our proto-oncogenes and wreak havoc. Bottom line wreak havoc. A very famous oncogenic virus is the human papillomavirus or HPV which is known to be responsible for 90% of cervical cancers around the world. And that's all about carcinogens.