Question

Which of the following is an example of post-transcriptional control of gene expression?

(A) the addition of methyl group to cytosine bases of DNA

(B) the binding of transcription factors to a promoter

(C) the removal of introns and alternative splicing of exons

(D) gene amplification contributing to cancer

Short answer

(A) The option “the addition of methyl group to cytosine bases of DNA” is false.

(B) The option “the binding of transcription factors to a promoter” is false.

(C) The option “the removal of introns and alternative splicing of exons” is true.

(D) The option “gene amplification contributing to cancer” is false.

Step-by-step solution

Transcription and post-transcriptional modifications

Transcription is the process of producing mRNA that is produced from the template strand. Post-transcriptional modifications occur after the transcription process. It involves the conversion of the pre-mRNA transcript into mature mRNA.

Explanation of option (A)

DNA methylation is the process that involves the addition of the methyl group to the DNA bases. It is the process that is associated with cell differentiation and proliferation.

DNA methylation is not a post-transcriptional process.

Therefore, the given statement is false.

Explanation of option (B)

The binding of transcription factors to the promoters is the initial step of transcription. After the binding of transcription factors, the polymerase binds to the DNA to start the process of transcription. It is not a post-transcriptional modification.

The post-transcriptional modification involves processes such as 5’ capping, poly-A tailing, and splicing. Post-transcriptional modification converts the pre-mRNA into mature mRNA to enter the process of translation. Therefore, the given statement is false.

Explanation of option (C)

Introns and exons are the regions present in the nascent mRNA that is produced from the DNA template. Introns are the non-coding region that needs to be removed from the mRNA. After the intron removal, the exons are joined together by the process of splicing.

The removal of introns and alternative splicing are the steps in the post-transcriptional modification that converts the mRNA into its mature form.

Therefore, the given statement is true.

Explanation of option (D)

The number of copies of genes is increased in the cells in the gene amplification. The genes are overamplified to form cancer cells. It happens at a faster rate compared to the transcription process.

Gene amplification is not post-transcriptional modifications.

Therefore, the given statement is false.