In a healthy human body, cells grow and behave based on the chromosomal information contained within each cell. A chromosome is a long molecule that contains the DNA sequence, and this is found in most living cells. DNA, meanwhile, is a molecule responsible for carrying the genes, but also tells them how to function. The reason why, for instance, we look like our parents is due to the fact that our DNA got some components from each of their DNAs. However, genes are responsible for a lot more than just outward appearance.

Every time a cell gets ready to divide itself into two cells, it has to copy the chromosomal DNA first. This is not a perfect process, and there are times when an error can occur. An error affects the genes that are contained in the DNA. Some of these genes are responsible for determining how each cell grows and divides. Oncogenes, for instance, are responsible for cell division and growth promotion. Tumor suppressor genes, meanwhile, are the ones that kill cells when they are redundant, and slow down the rate of division in other cells. A cancer is often caused by a mutation, or change, in the DNA. Often times, they switch tumor suppressor genes off, or oncogenes on. And those actions are believed to be one of the main chronic myelogenous leukemia or CML causes.

Chronic Myelogenous Leukemia or CML Causes:

Over the past few years, a lot of progress has been made on finding out the link between DNA mutations and bone marrow cells becoming leukemia cells. In fact, chronic myeloid leukemia, or CML, is one of the best understood cancers at the present time. In every human cell, there are 23 chromosomal pairs. When chromosomes nine and 22 start to divide, it is possible for some of the DNA to be swapped, and this is how CML starts. In other words, one of the main chronic myelogenous leukemia or CML causes is that some part of chromosome nine enters chromosome 22, and vice versa. This is called "translocation" and the result is that chromosome 22 becomes too short. The shortened and now abnormal chromosome 22 is called the "Philadelphia chromosome". Almost every CML patient has the Philadelphia chromosome.

When DNA is swapped between the two chromosomes, a new gene, which is an oncogene, is created. Specifically, this is the BCR-ABL, which produces the tyrosine kinase protein. In turn, this makes CML cells grow as well as reproduce out of control.

There is a small fraction of patients with CML who have BCR-ABL oncogene leukemia cells without the Philadelphia chromosome. It is believed that the oncogene is formed differently in those people. Very rarely, CML patients have neither the Philadelphia chromosome nor the BCR-ABL oncogene. They are not classed as true CML patients, and they usually have an unidentified oncogene that causes the cancer.

It is also possible for people to inherit mutations in their DNA from a parent. In this case, they are at an increased risk of certain types of cancer as well. However, an inherited mutation doesn't cause CML. Rather, the changes occur over the course of someone's life, not at birth.