Question

Which of these genome features control gene expression (when, where, and how much mRNA is made)?

a) Introns
b) Exons
c) Promoters
d) Codons

Answer 1

Promoters control gene expression by serving as binding sites for transcription factors that initiate the transcription process, which is the first step in gene expression.

Step-by-step explanation:

The feature of the genome that controls gene expression, including when, where, and how much mRNA is made, is c) Promoters.

Promoter regions are found immediately upstream of the coding sequence of a gene and serve as binding sites for transcription factors. These transcription factors control the initiation of transcription, which is the first step in gene expression.

Exons and introns are part of the gene structure, with exons being expressed in the form of mRNA after introns are removed during pre-mRNA splicing. However, it is the promoter that plays the critical role in controlling gene expression.

Answer 2

The component of the genome that controls gene expression is Promoters. Promoters are regions upstream of the gene that bind transcription factors to initiate transcription. Introns, exons, and codons have different roles in gene expression but are not directly responsible for initiating the process. Option c) Promoters is the correct answer.

Step-by-step explanation:

The feature of the genome that controls gene expression, which determines when, where, and how much mRNA is made, is c) Promoters. A promoter is the region of DNA that initiates transcription of a particular gene. It is located upstream of the coding sequence and serves as the binding site for RNA polymerase and other transcription factors.

These transcription factors regulate the initiation of transcription, effectively controlling gene expression. While introns may play a role in gene regulation and are removed during pre-mRNA processing, they do not encode proteins and are not directly responsible for the initiation of transcription.

Exons, on the other hand, are sequences present in protein-coding mRNA after the completion of pre-mRNA splicing and do not regulate the expression of genes. Codons are part of the genetic code that corresponds to amino acids in protein synthesis but do not control when and how genes are expressed.

It is essential for an organism to control the expression of its genes to make RNA and proteins when needed, in the right amount, and to stop production when no longer necessary. The mechanisms for gene expression involve complex interactions between promoter regions, transcription factors, mRNA transcripts, and the additional regulation that occurs after translation.