Biological Information Chapter 6

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Questions and Answers

What does the Central Dogma describe about the flow of genetic information?

From DNA to RNA to protein (correct)

From RNA to protein to DNA

From RNA to DNA to protein

From protein to RNA to DNA

Which of the following processes occurs during transcription?

DNA strands separate

Proteins are formed from RNA

RNA is synthesized from a DNA template (correct)

DNA is replicated

In semiconservative replication of DNA, what happens to the parental strands?

They are copied directly into proteins

They remain intact and are used as templates (correct)

They are destroyed

They form hybrid strands with RNA

Which enzyme is primarily responsible for synthesizing new DNA strands during replication?

DNA polymerase Signup and view all the answers

During translation, the role of mRNA is to:

Carry genetic information to ribosomes for protein synthesis Signup and view all the answers

What is the main purpose of the lac operon in gene regulation?

To enable the metabolism of lactose Signup and view all the answers

Which of the following statements about DNA replication is true?

It requires the unwinding of DNA helix Signup and view all the answers

Which phase of protein synthesis involves the creation of an mRNA transcript from a DNA template?

Transcription Signup and view all the answers

What direction is the lagging strand synthesized during DNA replication?

5' to 3' Signup and view all the answers

What is the role of RNA primers in the synthesis of the lagging strand?

To initiate DNA replication Signup and view all the answers

Which enzyme is responsible for replacing RNA primers with DNA nucleotides?

DNA Polymerase I Signup and view all the answers

What are the short segments formed on the lagging strand called?

Okazaki fragments Signup and view all the answers

What is the function of DNA Ligase during DNA replication?

To join Okazaki fragments Signup and view all the answers

How many RNA primers are required for synthesizing the lagging strand?

Multiple Signup and view all the answers

What is the end result of DNA replication?

Two identical copies of DNA, each with one parental and one new strand Signup and view all the answers

Which statement about Okazaki fragments is incorrect?

They are found on the leading strand. Signup and view all the answers

What is the primary enzyme responsible for the transcription of mRNA in eukaryotes?

RNA polymerase II Signup and view all the answers

During which stage of transcription does RNA polymerase II bind to the promoter region of DNA?

Initiation Signup and view all the answers

In which direction does RNA synthesis occur during transcription?

5' to 3' Signup and view all the answers

What happens during the elongation stage of transcription?

Nucleotides are added to the growing RNA transcript. Signup and view all the answers

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

Only one DNA strand (3' to 5') Signup and view all the answers

What is the termination stage in transcription characterized by?

The synthesis of RNA nucleotides halts. Signup and view all the answers

Which of these statements about the transcription process is incorrect?

Transcription requires ribosomes to function. Signup and view all the answers

What role does RNA polymerase II have during the transcription process?

It synthesizes RNA from a DNA template. Signup and view all the answers

What is the function of a codon in mRNA?

It encodes a specific amino acid. Signup and view all the answers

During transcription, where does the synthesis of RNA occur in eukaryotic cells?

In the nucleus Signup and view all the answers

Which statement is true about the genetic code?

It is non-overlapping and nearly universal across different organisms. Signup and view all the answers

What are the stages involved in the process of translation?

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

What is the role of the AUG codon in the genetic code?

It serves as a start codon. Signup and view all the answers

What are the three stop codons in the genetic code?

UAA, UAG, UGA Signup and view all the answers

Which of the following is NOT a characteristic of a codon?

It can code for more than one amino acid. Signup and view all the answers

In translation elongation, which event occurs first?

Codon recognition Signup and view all the answers

What is the function of β-galactosidase in the lac operon?

Hydrolyzes lactose into glucose and galactose Signup and view all the answers

What role does permease play in the lac operon?

Facilitates the transport of lactose into E. coli Signup and view all the answers

What happens to the lac operon when lactose is absent?

The repressor protein binds to the operator Signup and view all the answers

Which structure acts as a switch to activate or inactivate the lac operon?

Operator Signup and view all the answers

What is the role of allolactose in the mechanism of the lac operon?

It binds to the repressor protein and inactivates it Signup and view all the answers

In what form does RNA polymerase bind to the lac operon?

When the promoter is unblocked Signup and view all the answers

What does the regulatory gene lacI encode for?

Repressor protein Signup and view all the answers

What occurs during translation of the lac operon?

Three polypeptides are produced from one mRNA Signup and view all the answers

What happens when lactose is present in relation to the lac operon?

Transcription of structural genes occurs Signup and view all the answers

Which enzyme in the lac operon is responsible for detoxifying molecules entering the cell?

Transacetylase Signup and view all the answers

Study Notes

DNA and Genetic Information

Central Dogma describes the flow of genetic information from DNA to RNA to protein.
DNA is transcribed into mRNA, which serves as a template for protein synthesis during translation.

DNA Replication

Semiconservative replication involves separating the parental DNA strands, each serving as a template for new strands.
The lagging strand is synthesized discontinuously, away from the replication fork, in 5' to 3' direction, forming Okazaki fragments.
DNA Polymerase I removes RNA primers and replaces them with DNA nucleotides.
DNA Ligase joins Okazaki fragments, forming a continuous lagging strand, resulting in two identical DNA copies.

Protein Synthesis: Transcription and Translation

Transcription synthesizes RNA using a DNA template in the nucleus, while translation synthesizes polypeptides using mRNA in the cytoplasm.
Codons are sequences of three bases in mRNA that encode specific amino acids, allowing for 64 possible combinations to represent 20 amino acids.
Genetic code is nearly universal, with one start codon (AUG) and three stop codons (UAA, UAG, UGA).

Transcription Process

Occurs in three stages: initiation (RNA polymerase binds to the promoter and unwinds DNA), elongation (adding RNA nucleotides complementary to the DNA template), and termination.
RNA polymerase II is the enzyme responsible for transcribing in eukaryotes.

Lac Operon

Composed of structural genes (lacZ, lacY, lacA) encoded for β-galactosidase, permease, and transacetylase, respectively.
Regulatory gene (lacI) produces a repressor protein that binds to the operator, controlling operon activity.

Mechanism of Lac Operon

In the absence of lactose: Repressor binds to the operator, preventing RNA polymerase from transcribing structural genes; no proteins produced.
In the presence of lactose: Lactose is converted to allolactose, which binds to the repressor, making it inactive; RNA polymerase can bind to the promoter, activating the operon and facilitating transcription of structural genes, leading to protein production.

Summary

Transcription results in one mRNA translating into three polypeptides, demonstrating the efficient use of genetic information in cellular functions.

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Description

This quiz covers Chapter 6 on the expression of biological information, focusing on key topics such as DNA structure, replication, protein synthesis, and gene regulation. Prepare to test your knowledge on vital concepts like the lac operon and the processes of transcription and translation.