Question

The cancer gene ras produces mRNA containing an extra exon that includes a number of UAA codons. Cancer cells produce ras mRNA missing this exon. This mistake most likely is due to a mistake by __________.

Answer 1

The incorrect mRNA without the extra exon in the ras gene is most likely due to an error by spliceosomes, which are responsible for splicing mRNA during processing.

Step-by-step explanation:

The cancer gene ras is known for producing mRNA that should not normally contain an additional exon with several UAA codons. However, in cancer cells, the ras mRNA is produced without this extra exon, indicating a likely error in mRNA processing. This mistake is most likely due to a mistake by a spliceosome, which is responsible for removing introns (non-coding regions) and splicing together exons (coding regions) during mRNA processing. If spliceosomes fail to recognize the exon-intron boundaries properly, they might skip the inclusion of a vital exon or improperly include or exclude other parts of the mRNA transcript.