Question

1.       Define proto-oncogene and tumor suppressor gene. Compare and contrast the function and mechanism of action of these genes taking Ras and Rb as examples.

2.       What is the difference between maternal inheritance and X-linkage? Give specific examples.

3.       Define ‘single nucleotide polymorphism’.  How can SNPs be useful in genetics?

4.       Why do eukaryotic genes have introns? What are spliceosomes? What is alternative splicing?

5.       Give the definition of a promoter. Are the elements found in the proximal promoter and distal promoter regions the same for all eukaryotic genes? Explain.

Answer 1

1) a protooncogene is one which upon a gain of function mutation results in uncontrolled and faulty division and proliferation of cells. For eg. Ras is a signal transducer which when expressed contituitively or mutated in a way that it's constantly active results in its downstream signalling to be continuously on resulting in uncontrolled division.

On the other hand, tumor suppressor genes are those which inhibit cell division in their normal form but when mutated (loss of function mutation), this inhibition is relieved causing the cell to divide in an uncontrolled manner. Eg.Rb (retinoblastoma) protein is known to check cell division but when mutated to form a non-functional or a constitutively inactive protein the cell gets the freedom to divide continuously.