Question

1. Describe the role of proto-oncogenes/oncogenes OR tumor suppressor genes in the development of cancer.

2. RNA processing splices introns out of pre-mRNA producing mature mRNA. Describe what happens when some genes undergo alternative splicing.

Answer 1

Cancer is not a single disease. It is a collection of related diseases. There are two main types of genes that play an important role in cancer development.

a) Proto-oncogenes/oncogenes

b) tumor suppressor genes

Proto-oncogenes/Oncogenes - Proto-oncogenes are normal genes that helps cells to grow. Proto-oncogenes encode proteins which are involved in stimulation of cell division, inhibition of cell differentiation and preventing cell death. When proto-oncogenes are mutated it becomes oncogenes. Mutated proto-oncogenes turns cancerous. Oncogenes are genes that cause cancer. Oncogenes leads to increased production of these proteins. Cell growth occurs uncontrollably. Oncogenes are produced when proto-oncogenes are activated (turned on).

Proto-oncogenes become an oncogene due to

a) point mutation

b) gene amplification

c) chromosomal translocation

Tumor suppressor genes - The genes are involved in slowing down of cell division, programmmed cell death and repair DNA mistakes.Tumor suppressor genes causes cancer when they are inactivated (turned off). Mutations in these genes results in cells that are involved in normal inhibition of cell growth and division.

Alternative splicing

Splicing - Some section of RNA transcript (introns) are removed and the remaining sections (exons) are joined together.

Alternative splicing is a process of producing a variety of different proteins from a gene. Exons are joined together in different ways to generate multiple proteins. It changes the genomic instructions into functional proteins. It is important in regualtion of gene expression and protein diversity.It increases the diversity of the mRNA expressed from the genome.