AP Biology : Understanding Transcription Proteins

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #23 : Transcription

Histones are most closely linked to which of the following processes?

Possible Answers:

Crossing over of genetic information

Chromosome formation

Eukaryotic cell division

Synthesis of ATP in the nucleolus

Correct answer:

Chromosome formation

Explanation:

Histones are the packaging proteins on which long DNA molecules are coiled before mitosis. In this respect they are involved in cell division, but they are most closely linked to chromosome condensation. During interphase DNA is mostly packaged as euchromatin. Euchromatin is loosely packed and is capable of being transcribed, making it essential for protein synthesis and cell growth during the G1 and G2 phases. During mitosis the DNA condenses into tightly-packed heterochromatin in the form of chromosomes, which allow for cell division. The difference in packaging between euchromatin and heterochromatin comes from histone proteins. During chromosome formation, DNA becomes tightly wound around the histones to create the chromosome structure.

Example Question #24 : Transcription

Which of the following proteins is essential for transcription?

Possible Answers:

RNA polymerase

Primase

DNA polymerase

Trypsin

Correct answer:

RNA polymerase

Explanation:

RNA polymerase is the protein that synthesizes an RNA complement to a gene. RNA polymerase binds the template DNA strand and recruits ribonucleotides to build a strand of heteronuclear RNA (htRNA). The htRNA then undergoes modification to become mature mRNA before exiting the nucleus into the cytosol for translation.

DNA polymerase and primase are essential for the replication of DNA. DNA polymerase recruits nucleotides to synthesize the daughter strand of DNA, and primase creates small RNA primers to recruit DNA polymerase to the replication fork. Trypsin is a protease that is not involved in transcription; it helps to digest proteins in the small intestine.

Example Question #25 : Transcription

A researcher discovers a highly bizarre eukaryotic species whose mature mRNA do not contain poly-A tails. Which of the following proteins might this species also lack?

Possible Answers:

eEF1

eIF2

eIF4E

PABP

Correct answer:

PABP

Explanation:

PABP (poly-A-binding protein) binds to the poly-A tail in the 3' UTR of eukaryotic mRNA. It is likely that this species would not have a PABP homolog because it does not have a poly-A tail.

eIF4E binds to the 5' cap. eIF2 is responsible for bringing the first tRNA to the initiation complex. eEF1 is an elongation factor that helps bring tRNAs to the ribosome. 

Example Question #26 : Transcription

What is the central dogma of molecular biology?

Possible Answers:

DNA, Protein, RNA

Protien, DNA, RNA

RNA, DNA, Protein

RNA, Protein, DNA

DNA, RNA, Protein

Correct answer:

DNA, RNA, Protein

Explanation:

Proteins are coded for by RNA, which is coded for by DNA. The central dogma of molecular biology is the general sequence for the flow of information in coding for a protein. An mRNA strand is created using the DNA strand as a template. This new strand of mRNA then leaves the nucleus and is used as a template for 3-pronged tRNA molecules carrying amino acids to create a chain, which will eventually create a protein.

The central dogma of molecular biology is the general sequence of DNA to RNA to protein.

Example Question #27 : Transcription

The TATA box is bound by which of the following proteins?

Possible Answers:

DNA polymerase I

RNA polymerase I

Transcription factors

DNA polymerase III

RNA polymerase II

Correct answer:

Transcription factors

Explanation:

Transcription factors bind to the TATA box (found only in eukaryotes and archaea). The TATA box is a promoter region of a gene on the DNA. If the transcription factor that binds it is an activator, then it will interact with RNA polymerase II to form a transcription initiation complex and begin transcription of mRNA. DNA polymerases I and III are involved in DNA replication, and do not interact with the TATA box. RNA polymerase I is responsible for transcribing rRNA genes in the nucleolus.

Example Question #28 : Transcription

Which of the following are purines?

Possible Answers:

Adenine only

Cytosine and guanine

Guanine only 

Cytosine only

Adenine and guanine

Correct answer:

Adenine and guanine

Explanation:

To help remember which bases are purines and which are pyrimidines, there are two acronyms. Pure As Gold. Adenine and guanine are purines because of their structure. Also, pyrimidines, like pyramids, are "sharp". Sharp things CUT (cytosine, uracil and thymine).

Example Question #29 : Transcription

Which statement is true regarding DNA?

Possible Answers:

It is a single-stranded molecule

It contains adenine, guanine, cytosine, and thymine

It cannot be replicated

It is a protein

It contains adenine, guanine, cytosine, and uracil

Correct answer:

It contains adenine, guanine, cytosine, and thymine

Explanation:

DNA is a nucleic acid, made up of the nucleotides, which contain a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases. These bases are adenine, cytosine, guanine, and thymine. DNA is double-stranded, but transiently single-stranded during DNA replication and transcription.

Example Question #30 : Transcription

What is the role of an activator?

Possible Answers:

Binds to RNA polymerase to initiate transcription 

Increases transcription of a specific gene

Activates transcription of the entire genome

Decreases transcription of a specific gene

Correct answer:

Increases transcription of a specific gene

Explanation:

Activators are proteins that increase transcription of a specific gene. Activators bind to promoters and often coactivators to facilitate binding of the pre-activation complex and initiation complexes; therefore, they stimulate the transcription of a given gene. 

Example Question #1 : Understanding Transcription Proteins

Where does RNA polymerase bind during transcription?

Possible Answers:

RNA polymerase binds to the promoter sequence within the DNA template.

RNA polymerase binds to the activators.

RNA polymerase binds to the transcription factors. 

RNA polymerase binds to the sequence downstream of the promoter sequence.

Correct answer:

RNA polymerase binds to the promoter sequence within the DNA template.

Explanation:

During transcription, RNA polymerase enzymes bind to DNA promoter sequences. This binding is facilitated by the pre-initiation complex (composed of transcription factors, the promoter sequence, activators, and repressors) as well as RNA polymerase. In eukaryotic cells, certain transcription factors must bind to the promoter sequence before RNA polymerase can. This is due to an inability of RNA polymerase to independently recognize the promoter sequence. Once RNA polymerase does bind, transcription can be initiated. 

Example Question #2 : Understanding Transcription Proteins

Which of the following proteins play a role in proofreading during transcription?

Possible Answers:

Activators

RNA polymerase

RNA ligase

Transcription factors

Correct answer:

RNA polymerase

Explanation:

Proofreading occurs during the elongation phase of transcription. RNA polymerase's movement over the DNA template strand includes a backtracking motion that allows RNA polymerase to proofread the newly synthesized RNA transcript.

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