You have isolated and sequenced a region of DNA that appears to have caused tumor formation. For what types of mutations would you look to understand how that DNA causes the cancer and what is the characteristic of each type of mutation you might find?

Question

What will be an ideal response?

Answer 1

Answer:
(a) Point mutation: A single base-pair change substitution could change an amino acid in an encoded protein that activates the activity of an oncogene product or inactivates a tumor suppressor gene product.
(b) Local DNA rearrangement: The DNA may have an insertion, deletion, inversion, or transposition that converts a proto-oncogene to an oncogene of disrupts a tumor suppressor gene. (c) Gene amplification: creates multiple copies of a gene, which causes overactivity of the gene product, because it is overexpressed.
(d) Chromosomal translocation: The DNA could have moved to a different part of the same chromosome or to a different chromosome. This may fuse two genes together to form an oncogene encoding an abnormal protein, or it may place a proto-oncogene next to a highly active gene, thereby causing the translocated proto-oncogene to become more active.
(e) Insertional mutagenesis: Like translocation, movement of the DNA may integrate it near a proto-oncogene, stimulating its expression, or into a tumor suppressor gene, preventing expression of a functional protein.