High School Biology : Understanding Transcription Proteins

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Transcription

Which of the following proteins is responsible for transcribing messenger RNA?

Possible Answers:

RNA polymerase I

DNA polymerase

RNA polymerase II

RNA polymerase III

Correct answer:

RNA polymerase II

Explanation:

RNA polymerase II is the primary protein responsible for generating mRNA.

RNA polymerases I and III transcribe other RNAs (such as tRNA and rRNA). DNA polymerase is responsible for DNA replication during the S phase of the cell cycle.

Example Question #2 : Transcription

Transcription factors bind to __________, after which RNA polymerase can bind to these transcription factors in order to open the DNA double helix. 

Possible Answers:

the 3' side of the DNA strand

a peptide strand

a gene

promoter sites

a ribosome

Correct answer:

promoter sites

Explanation:

During transcription, transcription factors will bind to promoter sites on the 5' side of the gene to be transcribed. Although the answer "a gene" is technically correct, the more accurate answer is promoter site—the region of DNA that initiates transcription. 

A peptide strand is the product of translation, and does not bind transcription factors. 

Ribosomes help read the RNA that is eventually transcribed from the DNA, but transcription factors do not interact directly with the ribosomes. 

Example Question #1 : Rna

Where in a plant cell is mRNA synthesized?

Possible Answers:

The cytoplasm

The nucleolus

The ribosome

The nucleus

The Golgi apparatus

Correct answer:

The nucleus

Explanation:

Plant cells are eukaryotic, thus they have nuclei. The process of mRNA synthesis is called transcription. Transcription occurs in the nucleus in eukaryotes. In prokaryotes, it occurs in the cytoplasm. Note that rRNA synthesis and ribosome assembly takes place in the nucleolus. 

Example Question #4 : Transcription

What would most likely result from the insertion of a single nucleotide during transcription?

Possible Answers:

None of these

No mRNA will be produced

A frameshift mutation

A truncated protein

A truncated mRNA molecule

Correct answer:

A frameshift mutation

Explanation:

The genetic code is read in triplets. The addition of a single nucleotide would shift the triplets such that they are no longer read in the correct frame. This is called a frameshift mutation. A truncated protein could be a result of an insertion, but this is not the most likely result. Early transcriptional termination would not be a likely result of an insertion, since this is mediated by long GC repeats or a protein called rho in prokaryotes. Eukaryotic transcriptional termination is not well-understood.

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