Biology 2.1 - 2.2 Transcription in Molecular Biology

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Questions and Answers

What is the primary result of the information encoded in an individual mRNA?

Synthesis of a polypeptide (correct)

Formation of multiple proteins at once

Production of lipids

Synthesis of a nucleotide

In eukaryotic organisms, where does transcription occur?

In the mitochondria

In the ribosomes

In the cytoplasm

In the nucleus (correct)

What is a significant difference between prokaryotic and eukaryotic gene expression?

Prokaryotic cells have multiple RNA types

Eukaryotic genes are expressed without regulation

Eukaryotic cells do not use transcription

Eukaryotic transcription and translation are separated in space and time (correct)

Why do prokaryotic organisms generally not have a nucleus?

Their DNA is distributed throughout the cell Signup and view all the answers

What is the main function of the 5' cap added to pre-mRNA?

To prevent degradation of mRNA in the cytoplasm Signup and view all the answers

Which modification is made to the 3' end of pre-mRNA?

Addition of a poly-A tail Signup and view all the answers

Which statement about polypeptide chains is correct?

They consist of multiple amino acids joined together Signup and view all the answers

Genomic DNA can be categorized based on what characteristics?

Nucleotide composition, sequence structure, and coding potential Signup and view all the answers

What is the role of the poly-A tail in mRNA processing?

It prevents mRNA degradation and aids in export Signup and view all the answers

What is the nature of the 5' cap added to pre-mRNA?

A modified guanosine triphosphate (GTP) Signup and view all the answers

What typically occurs after transcription in eukaryotic cells?

Translation of mRNA into protein Signup and view all the answers

Which statement is true about eukaryotic mRNA versus prokaryotic mRNA?

Eukaryotic mRNA undergoes modifications such as capping and polyadenylation Signup and view all the answers

Which feature differentiates eukaryotes from prokaryotes regarding gene expression?

The separation of transcription and translation processes Signup and view all the answers

What is the primary role of RNA polymerase ll in transcription?

To build the mRNA molecule. Signup and view all the answers

Which strand of DNA serves as the template for mRNA synthesis during transcription?

Noncoding (antisense) strand. Signup and view all the answers

What is formed when RNA polymerase ll encounters the terminator sequence?

Transcription is terminated. Signup and view all the answers

The mRNA transcript is synthesized in which direction?

5' to 3' Signup and view all the answers

How does the sequence of the mRNA compare to the coding DNA strand?

It has the same sequence except that thymine in DNA is replaced by uracil in mRNA. Signup and view all the answers

What occurs during the elongation phase of transcription?

The noncoding DNA strand serves as a template for mRNA. Signup and view all the answers

Which factor can influence the rate of transcription initiation?

The efficiency of RNA polymerase ll. Signup and view all the answers

What happens to the DNA double helix after RNA polymerase ll progresses along the template strand?

It reforms behind the enzyme. Signup and view all the answers

Which of the following statements is true regarding the transcription initiation complex?

It assembles at the promoter region. Signup and view all the answers

What happens to the mRNA transcript in prokaryotes after transcription?

It detaches from the DNA and is available for translation. Signup and view all the answers

What is the role of the polyadenylation signal sequence in eukaryotic transcription?

To provide a signal for mRNA separation from RNA polymerase II. Signup and view all the answers

What is pre-mRNA primarily characterized by in eukaryotes?

It still contains introns and is not yet processed. Signup and view all the answers

Which enzyme is responsible for transcription in eukaryotes?

RNA polymerase II Signup and view all the answers

How is mRNA processed in eukaryotes before it exits the nucleus?

It is modified by adding a 5' cap and a poly-A tail. Signup and view all the answers

In the process of transcription termination in eukaryotes, what occurs after the RNA polymerase II transcribes the polyadenylation signal?

Proteins bind to the signal, leading to mRNA release. Signup and view all the answers

Which statement is true regarding mRNA transcripts in prokaryotic cells?

They are translated while being transcribed. Signup and view all the answers

What type of RNA is specifically responsible for carrying information needed for protein synthesis?

mRNA Signup and view all the answers

What modification occurs to mRNA during eukaryotic transcription that does not occur in prokaryotes?

Addition of a 5' cap and polyadenylation at the 3' end. Signup and view all the answers

Which sequence of nucleotides marks the beginning of a transcription unit?

Promoter Signup and view all the answers

Which component is NOT involved in the process of transcription termination in eukaryotes?

RNA polymerase III. Signup and view all the answers

What is the primary function of RNA polymerase II in transcription?

It synthesizes mRNA molecules. Signup and view all the answers

What is a primary function of the terminator region in transcription?

To signal the end of the transcription. Signup and view all the answers

In which direction does RNA polymerase II assemble nucleotides during transcription?

5' to 3' Signup and view all the answers

Which specific sequence is known for its universal occurrence in promoter regions?

TATA box Signup and view all the answers

What are the three basic stages of transcription?

Initiation, elongation, and termination Signup and view all the answers

Where is the transcription start site located relative to the promoter?

Downstream of the promoter Signup and view all the answers

What is the primary role of the terminator in transcription?

To signal the end of transcription Signup and view all the answers

What occurs during the initiation stage of transcription?

The transcription initiation complex forms. Signup and view all the answers

What does 'upstream' refer to in the context of a transcription unit?

Before the coding region begins Signup and view all the answers

Study Notes

Transcription

Central Dogma of Molecular Biology explains the flow of genetic information from DNA to RNA to protein.
Transcription is the process of copying DNA into RNA.
RNA Polymerase II is the enzyme that synthesizes mRNA, it can assemble nucleotides in the 5' to 3' direction.
Transcription Unit is a segment of DNA that contains a promoter, a gene, and a terminator.
Promoter is a DNA sequence that signals the start of transcription.
Terminator is a DNA sequence that signals the end of transcription.

### Mechanism of Transcription

Initiation starts with the recognition of the promoter sequence by RNA polymerase II and general transcription factors.
TATA box is a common promoter sequence with thymine (T) and adenine (A) nucleotides.
Elongation involves RNA polymerase II using the noncoding DNA strand (3' to 5') as a template to assemble mRNA in the 5' to 3' direction.
Termination occurs when RNA polymerase II reaches the terminator sequence in the DNA.

Modifications to mRNA Ends

5' cap is a modified guanosine triphosphate (GTP) nucleotide added to the 5' end of pre-mRNA.
Poly-A tail is a chain of adenine nucleotides added to the 3' end of pre-mRNA.
5' cap and poly-A tail prevent mRNA degradation, facilitate export from the nucleus, and are recognized by the ribosome for translation.

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Description

Explore the key concepts of transcription in molecular biology, focusing on the Central Dogma. This quiz covers the roles of RNA Polymerase II, transcription units, promoters, and the process of initiation, elongation, and termination of transcription.