Please help!

Question

I need help for the following questions. Thanks!!!

 

1. What are growth factors? Explain how they function to control cell division and differentiation.

My answer:

      A growth factor is a naturally occurring substance capable of stimulating cellular growth, proliferation and differentiation. Usually it is a protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes.

     Growth factors typically act as signaling molecules between cells. Examples are cytokines and hormones that bind to specific receptor on the surface of their target cells.

     They often promote cell differentiation and maturation, which varies between growth factor. For example, bone morphogenic proteins stimulate bone cell differentiation, while fibroblast growth factors and vascular endothelial growth factors stimulate blood vessel differentiation (angiogenesis).

 

2.   What are proto-oncogenes? What do they do? What happens when proto-oncogenes become oncogenes?

My answer:

      A proto-oncogene is a normal gene that has many different functions in the cell. Some proto-oncogenes provide signals that read to cell division. Other proto-oncogenes regulate programmed cell death (apoptosis). Apoptosis leads to the elimination of cells without releasing harmful substances into the surrounding area. Apoptosis plays a crucial role in developing and maintaining health by eliminating old cells, unnecessary cells, and unhealthy cells. When a proto-oncogene becomes mutilated it becomes a oncogene. This causes the cell to divide in an unregulated manner. An oncogene may contribute to the growth of a tumor, which may be cancerous.

 

3.   What is the function of a tumor-suppressor gene?

My answer:

       Tumor-suppressor genes regulate and stop cell division.

       An example is P53 which causes cells with DNA damage to undergo programmed cell death (apoptosis). This prevents them forming tumor.

Answer 1

This is well written and a good explanation.  I noticed that you used “read” and probably meant “lead.” I might add that signaling molecules which bind to receptors on the outside of the cell membrane often trigger downstream events inside the cell such as the release of DNA binding proteins which may activate or repress the expression of certain genes.

Many of the processes you describe are based on the regulation of gene expression.  Expressed genes are simply genes which are actively producing RNA transcripts and in turn, those transcripts can be translated into functioning proteins. Generally in these processes there is a chain of signaling and activation/repression which is highly regulated. Keep in mind that repression is often as important, or more important than activation.

Answer 2

Thank you for your help, anonymous!!!