Question

Eukaryotic transcription A. is independent of the presence of upstream consensus sequences. B. may involve a promoter located within the region transcribed rather than upstream. C. requires a separate promoter region for each of the three ribosomal RNAs transcribed. D. requires that the entire gene be in the nucleosome form of chromatin. E. is affected by enhancer sequences only if they are adjacent to the promoter.

Short answer

A) It is independent of the presence of upstream consensus sequences. B) The promoter may be located within the transcribed region rather than being only upstream. C) It requires a separate promoter region for each of the three ribosomal RNAs that are transcribed. D) It requires the entire gene to be in the nucleosome form. E) It is influenced by the proximity of enhancer sequences to the promoter. Answer: B) The promoter may be located within the transcribed region rather than being only upstream.

Step-by-step solution

Understanding Eukaryotic Transcription

Eukaryotic transcription is the process of synthesizing RNA from a DNA template. This process is regulated by various elements, including promoters, enhancer sequences, and the chromatin structure. It requires the collaboration of numerous proteins and factors that bind to specific DNA sequences to ensure the appropriate synthesis of RNA.

Analyze Option A

Option A states that eukaryotic transcription is independent of the presence of upstream consensus sequences. However, upstream consensus sequences, such as TATA box and other core promoter elements, play a crucial role in the initiation of transcription by serving as binding sites for transcription factors and RNA polymerase. Therefore, option A is incorrect.

Analyze Option B

Option B suggests that the promoter might be located within the transcribed region rather than upstream. In some cases, eukaryotic genes may have internal promoters, which are located within the gene itself. Thus, option B is correct.

Analyze Option C

Option C says that eukaryotic transcription requires a separate promoter region for each of the three ribosomal RNAs transcribed. However, in eukaryotes, the 18S, 5.8S, and 28S ribosomal RNAs are transcribed as a single precursor RNA molecule, which is then processed to create the individual rRNAs. They are transcribed by RNA polymerase I using a single promoter. Therefore, option C is incorrect.

Analyze Option D

Option D claims that eukaryotic transcription requires the entire gene to be in nucleosome form. However, during transcription, the chromatin structure undergoes changes, with certain regions getting more or less condensed to accommodate the transcription machinery. The entire gene does not need to be in nucleosome form for transcription to occur. Thus, option D is incorrect.

Analyze Option E

Option E states that eukaryotic transcription is affected by enhancer sequences only if they are adjacent to the promoter. Enhancers are regulatory elements that facilitate the initiation of transcription by providing binding sites for transcription factors, and they can be located far from the promoter they regulate or even in introns. Enhancers can act on promoters at a distance, so option E is incorrect.

Choose the correct statement

Based on the analysis of each option, option B is the correct statement about eukaryotic transcription, as it states that the promoter may be located within the transcribed region rather than upstream. Such internal promoters can be found in some cases in eukaryotic genes.