Question

All of our cells contain protooncogenes that may turn into oncogenes, which are cancer genes. Which statement best describes the protooncogenes?
A. Came into our cells from a viral infection of our ancestors
B. Arose from plasmids that have been inserted into bacteria and now reside in us
C. Are DNA 'junk" with no known function
D. Turn into oncogenes as we age
E. Help regulate cell division

Answer 1

Hint: Proto Oncogenes are genes that encode for proteins that are responsible for proliferation. When there is a mutation in proto-oncogenes this will lead to an increase in protein expression. The mutated form of genes is called an oncogene. Another mechanism that leads to tumor proliferation is by antiproliferative tumor suppressor gene.

Complete step by step answer:
Proto-oncogene- when a normal gene is altered by mutation becomes an oncogene which will lead to cancer. Proto-oncogene will have many different functions in the cell. Some proto-oncogenes provide signals which will activate cell division.
The defective versions of proto-oncogenes are known as oncogenes which cause the cell to divide in an unregulated manner. This growth will occur in the absence of normal growth signals such as provided by growth factors. The key feature of this oncogene activity is the signal which is altered by a single copy of the gene which leads to an unregulated mass of growth.

Hence the correct answer is option E, Help regulate cell division.

Note:
Any gene which encodes for a protein that is capable of transforming the cell in culture media or induction of cancer in animals is referred to as oncogenes. The normal gene from which it arises is called proto-oncogenes which comprise one category of normal growth regulator genes that promote cell division. When these genes are mutated it leads to the uncontrolled multiplication of cell division. Oncogenes were originally identified in viruses causing cancers. These are called transformation viruses (often retrovirus) as they change the growth pattern of cells from normal to tumor-like. Of the many known oncogenes, all but a few are derived from normal cellular genes (i.e., proto-oncogenes) whose products participate in cellular growth-controlling pathways. For example, the ras gene discussed previously is a proto-oncogene that encodes an intracellular signal-transduction protein.