Tag: non-infectious diseases

A retrovirus has been identified as a single-stranded positive sense RNA virus which has an intermediate DNA that helps it target the host cell as an obligate parasite. This virus reverses the usual pattern and uses its transcriptase enzyme to produce DNA. The transmission of these viruses been generally cell-to-cell. In human beings, cancer can be triggered by proto-oncogenes present in the retrovirus which are mistakenly incorporated into proviral DNA or by the disruption of the cellular proto-oncogenes

• Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
  
• Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumors. Tumors can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumors that stay in one spot and demonstrate limited growth are generally considered to be benign.
  

 Polycythemia is a disease state in which the hematocrit (the volume % of RBC in the Blood) is elevated.It can be due to an increase in the number of RBC ("absolute polycythemia") or to a decrease in the volume of plasma ("relative polycythemia").

'Philadelphia chromosome' is found in the patient suffering from leukaemia. The main cause is a genetic abnormality in chromosome 22 of leukaemia cancer cells. The chromosome is short due to a reciprocal translocation between chromosome 9 and chromosome 22 and contains a fusion gene called BCR-ABL1 which is juxtaposed onto the BCR gene of chromosome 22, coding for a hybrid protein, a tyrosine kinase signalling protein which causes rapid multiplication of the cell.

Oncogenes are genes that has the potential to cause cancer.
Estrogens are a group of hormones that are important for female sexual and reproductive development.
Carcinogens are substances, radionuclide or radiation that is an agent directly involved in causing cancer.
Therefore, the correct answer is option D.

The spread of tumour cells through vascular system (blood, lymph) from the site of formation to other parts of the body is known as metastasis.

The ozone layer is present in the stratosphere above the Earth. The layer of ozone is responsible for the absorption of the harmful ultraviolet radiations from the solar radiations. These radiations are prevented from entering the Earth's atmosphere to prevent the development of skin cancer. The radiations can also damage the eye and other exposed parts of the body. 

Carcinogen is a substance or agent that can cause cells to become cancerous by altering their genetic structure so that they multiply continuously and become malignant. Asbestos, DDT, and tobacco smoke are examples of carcinogens.