Cytogenetics is a branch of genetics that is concerned with the study of the structure and function of the cell, especially the chromosomes.
Cancer (medical term: malignant neoplasm) is a class of diseases in which a group of cells display uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). The branch of medicine concerned with the study, diagnosis, treatment, and prevention of cancer is oncology.Cancer may affect people at all ages, even fetuses, but the risk for most varieties increases with age. Nearly all cancers are caused by abnormalities in the genetic material of the transformed cells. These abnormalities may be due to the effects of carcinogens, such as tobacco smoke, radiation, chemicals, or infectious agents.Cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or are inherited, and thus present in all cells from birth.
Types of Cancer:
There are hundred types of cancer. Some of them are discussed below;
- Carcinomas: The majority of cancers, (85%), are carcinomas.
- Leukaemias and lymphomas: Quite rare and make up about 6.5% of all cancers.
- Sarcomas: They account for less than 1% (1 in 100) of cancers.
- Otherforms of cancer: Brain tumours and other very rare forms of cancer.
A benign tumor is a tumor that lacks all three of the malignant properties of a cancer.
Malignant (from the Latin roots mal- = “bad” and -genus = “born”) is a medical term used to describe a severe and progressively worsening disease. Malignant tumor is synonymous with cancer.
Genetic abnormalities found in cancer typically affect two general classes of genes. Cancer-promoting oncogenes are typically activated in cancer cells, giving those cells new properties, such as hyperactive growth and division, protection against programmed cell death, loss of respect for normal tissue boundaries, and the ability to become established in diverse tissue environments. Tumor suppressor genes are then inactivated in cancer cells, resulting in the loss of normal functions in those cells, such as accurate DNA replication, control over the cell cycle, orientation and adhesion within tissues, and interaction with protective cells of the immune system.
How Genes Cause Cancer?
Genes come in pairs, and work together to make a protein product. One member of the gene pair comes from the mother, while the other member is inherited from the father. Eggs and sperm are called “germ cells.” When an alteration or mutation in a gene is present in the germ cells, it is referred to as a “germline mutation.” When a germline mutation is inherited, it is present in all body cells. On the other hand, mutations that we are not born with, but that occur by chance over time in cells of the body are said to be “acquired.” Acquired mutations are not present in all cells of the body, are not inherited, and are not passed down to our children. Acquired mutations are always involved in causing cancer. Germline mutations are involved in a small percentage of cases.
The formation of tumors basically results from cell growth that gets out of control. In the human genome, there are many different types of genes that control cell growth in a very systematic, precise way. When these genes have an error in their DNA code, they may not work properly, and are said to be “altered” or mutated. An accumulation of many mutations in different genes occurring in a specific group of cells over time is required to cause malignancy. The different types of genes, that when mutated, can lead to the development of cancer
These are altered forms of genes known as proto-oncogenes. Proto-oncogenes are responsible for promoting cell growth. When altered or mutated, they become oncogenes and then can promote tumor formation or growth
Tumor Suppressor Genes
Tumor suppressor genes are genes normally present in our cells. When working properly, they control the processes of cell growth and cell death (called apoptosis. When a tumor suppressor gene is mutated, this can lead to tumor formation or growth.Tumor suppressor genes are said to be “recessive” at the cellular level.Most of the genes associated with hereditary cancer are tumor suppressor genes.
DNA repair genes
During cell division, the DNA in a cell makes a copy or replica of itself. When these genes are altered or mutated, however, mismatches (mistakes) in the DNA remain. If these mistakes occur in tumor suppressor genes or proto-oncogenes, eventually this will lead to uncontrolled cell growth and tumor formation.Mutations in DNA repair genes can be inherited from a parent or acquired over time as the result of aging and environmental exposures.Because it takes more than a single mutation to cause cancer, not all people who inherit a mutation in a tumor suppressor gene, proto-oncogene, or DNA repair gene will develop cancer.
Other important risk factors are;Food, Radiations, Tobacco, Weight and physical Activity, Environment, Age, Immune System.