Question

please explain these three things :

1.) a protooncogene and it’s function and how it differs from a normal version of the gene when it’s cancerous

2.) why so many cancer cells duplicate uncontrollably vs normal cells and why normal cells only divide 20 times

3.) how dna turns into pre rna and then mrna , and draw an example

Answer 1

1) Protooncogenes are those genes that control the cell cycle. If protooncogenes become mutated then they are transformed as oncogenes. Oncogenes are responsible for the onset of cancer.

There are several functions of protooncogenes. They are -

a) They function to make the proteins for the cell cycle checkpoints. Cell cycle checkpoints can check the unregulated cell division.

b) Protooncogenes are responsible for helping the abnormal cells (such as DNA damage) to apotheosis.

c) Some types of tumour repressor genes are produced from the protooncogenes.

When protooncogenes are mutated to oncogenes then they promote uncontrolled cell division, help the cells to avoid apoptosis.

2) The telomere of each DNA becomes shorted after each cycle of cell division. So, there is a chance to DNA damage when cells are being decided after certain cycle. Hence, normal cells only divide 20 times. But the cancerous cells don't maintain the quality of the cell. They can devide beyond the limit.

3) Eukaryotic DNA is composed of exon and intron parts. For this reason when pre-mRNA is transcribed (by the process of transcription) then it carries all the exon and intron parts as it follows the template strand for being synthesised. But, later on the intron parts are spliced out from the pre-mRNA by the process of splicing. Thus a mature mRNA is produced.

For example, when insulin gene is transcribed then a pre-mRNA is produced. After the process of splicing, the intron parts are spliced out and a mature insulin mRNA is produced. From this mature mRNA the insulin protein is translated by the process of translation.