Gene Expression and Protein Production
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Questions and Answers

What does "gene expression at the molecular level" affect?

The structure and function of cells, ultimately determining the traits an organism expresses.

What are the three steps involved in gene expression?

  1. Using a gene as a template to create an RNA molecule. 2. Modifying the RNA into a functional molecule in eukaryotes. 3. Using RNA to direct the formation of a protein.

What are genes that encode polypeptides called?

Protein-encoding genes

What are changes in genetic material that can be inherited called?

<p>Mutations</p> Signup and view all the answers

What did research on the effects of mutations help to determine?

<p>The molecular function of genes</p> Signup and view all the answers

At what two levels can we look at gene function?

<p>Molecular function and organism's trait</p> Signup and view all the answers

At what level does gene function relate to the protein product?

<p>Molecular function</p> Signup and view all the answers

At what level does gene function relate to the characteristic conferred by the gene?

<p>Organism's trait</p> Signup and view all the answers

The "one gene, one enzyme" hypothesis was the original understanding of gene expression.

<p>True</p> Signup and view all the answers

What is the modern understanding of gene expression, replacing the "one gene, one enzyme" hypothesis??

<p>One gene, one polypeptide</p> Signup and view all the answers

What is the name of the hypothesis that stated that a single gene controlled the synthesis of a single enzyme?

<p>This hypothesis, proposed by Beadle and Tatum, was groundbreaking in understanding the relationship between genes and enzymes.</p> Signup and view all the answers

The "one gene, one polypeptide" hypothesis applies to all proteins.

<p>False</p> Signup and view all the answers

What does the term "polypeptide" refer to?

<p>A linear sequence of amino acids</p> Signup and view all the answers

When comparing the term "polypeptide" to "protein", what does the term "protein" denote?

<p>Function</p> Signup and view all the answers

A single gene can contain the information to make a single protein, even if it's composed of multiple polypeptides.

<p>False</p> Signup and view all the answers

What protein carries oxygen in red blood cells and is composed of two alpha globin and two beta globin polypeptides?

<p>Hemoglobin</p> Signup and view all the answers

A single gene can encode more than one polypeptide through alternative splicing of mRNA.

<p>True</p> Signup and view all the answers

All genes encode for polypeptides.

<p>False</p> Signup and view all the answers

What are the two main steps of gene expression?

<p>Transcription and translation</p> Signup and view all the answers

What does the term "transcription" literally mean?

<p>The act of making a copy</p> Signup and view all the answers

What is messenger RNA (mRNA) and why is it called that?

<p>Messenger RNA is a type of RNA that carries genetic information from DNA to ribosomes, where proteins are synthesized.</p> Signup and view all the answers

What is the second step of gene expression?

<p>Translation</p> Signup and view all the answers

Why is the second step of gene expression called "translation"?

<p>A base sequence in an mRNA is translated into an amino acid sequence of a polypeptide.</p> Signup and view all the answers

What is the name given to the process of transcription from DNA to mRNA and the translation of mRNA into a polypeptide?

<p>The central dogma of gene expression</p> Signup and view all the answers

What does transcription produce?

<p>A transcript (RNA copy) of a gene, which is messenger RNA (mRNA) that specifies the amino acid sequence of a polypeptide.</p> Signup and view all the answers

What does translation involve?

<p>Synthesizing a specific polypeptide on a ribosome using the mRNA template.</p> Signup and view all the answers

Provide a 3-word summary of the central dogma of gene expression.

<p>DNA -&gt; RNA -&gt; Protein</p> Signup and view all the answers

What are the two types of RNA that are not translated into proteins?

<p>Structural and regulatory RNAs</p> Signup and view all the answers

RNA processing occurs before transcription in eukaryotes.

<p>False</p> Signup and view all the answers

Where do transcription and translation occur in bacteria?

<p>The cytoplasm</p> Signup and view all the answers

Where do transcription and translation occur in eukaryotes?

<p>Transcription occurs in the nucleus and translation occurs in the cytosol.</p> Signup and view all the answers

The flow of genetic information from DNA to RNA to protein is the only pathway for gene expression.

<p>False</p> Signup and view all the answers

What is the role of the genetic material?

<p>To encode the production of proteins in the correct cell, at the proper time, and in suitable amounts</p> Signup and view all the answers

What do structural genes code for?

<p>Polypeptides</p> Signup and view all the answers

What do one or several polypeptides act as?

<p>A protein</p> Signup and view all the answers

What do the activities of proteins determine?

<p>The structure and function of cells, and ultimately the traits of an organism</p> Signup and view all the answers

What does the genetic material provide?

<p>A blueprint for the characteristics of every organism</p> Signup and view all the answers

What does each protein-encoding gene store the information for?

<p>The production of a polypeptide, which becomes a unit within a functional protein</p> Signup and view all the answers

What is the key purpose of the genetic material?

<p>To encode the production of proteins in the correct cell, at the proper time, and in suitable amounts</p> Signup and view all the answers

What is a gene?

<p>An organized unit of DNA sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product</p> Signup and view all the answers

What does transfer RNA (tRNA) do?

<p>Translates mRNA into amino acids</p> Signup and view all the answers

What does ribosomal RNA (rRNA) do?

<p>Forms part of ribosomes</p> Signup and view all the answers

How is a working copy of a DNA sequence made for gene expression?

<p>By the process of transcription, in which a DNA sequence is copied into an RNA sequence</p> Signup and view all the answers

Transcription permanently alters the DNA structure.

<p>False</p> Signup and view all the answers

What is made when a protein-encoding gene is transcribed?

<p>mRNA</p> Signup and view all the answers

What happens to the polypeptide after it is made?

<p>It becomes a functional protein</p> Signup and view all the answers

Most genes are protein-encoding genes.

<p>True</p> Signup and view all the answers

What is non-coding RNA and when is it produced?

<p>Non-coding RNA is RNA that is not translated into protein. It is produced when a gene does not encode for a polypeptide, and the functional product is the RNA itself.</p> Signup and view all the answers

What are two common types of non-coding RNA?

<p>Transfer RNA (tRNA) and ribosomal RNA (rRNA)</p> Signup and view all the answers

What is a gene composed of?

<p>Specific base sequences organized in a way that allows the DNA to be transcribed into RNA</p> Signup and view all the answers

What is a promoter in transcription?

<p>A sequence of DNA that controls when and where transcription will begin</p> Signup and view all the answers

What does the terminator in transcription specify ?

<p>The end of transcription</p> Signup and view all the answers

What are the two boundaries between which transcription occurs?

<p>The promoter (start) and terminator (end)</p> Signup and view all the answers

What does the promoter signal?

<p>The beginning of transcription</p> Signup and view all the answers

What does the terminator signal?

<p>The end of transcription</p> Signup and view all the answers

What does the transcribed region in transcription contain?

<p>Information that specifies an amino acid sequence</p> Signup and view all the answers

What do regulatory sequences in transcription function as?

<p>Sites for the binding of regulatory proteins, which influence the rate of transcription</p> Signup and view all the answers

What is the direction of transcription from DNA to mRNA?

<p>From the end of the promoter through the coding sequence to the terminator</p> Signup and view all the answers

What is the function of regulatory sequences in transcription?

<p>They function as sites for the binding of regulatory proteins, which can enhance or inhibit the rate of transcription</p> Signup and view all the answers

What is the role of sigma factor in transcription initiation?

<p>Sigma factor binds to RNA polymerase and recognizes the base sequence of a promoter.</p> Signup and view all the answers

What is the function of RNA polymerase in transcription initiation?

<p>RNA polymerase binds to sigma factor and the promoter, unwinding the DNA to form an open complex.</p> Signup and view all the answers

What does the term "template strand" refer to in transcription elongation?

<p>The DNA strand that is used as a template for RNA synthesis</p> Signup and view all the answers

What is the name given to the opposite DNA strand in transcription elongation?

<p>Coding strand</p> Signup and view all the answers

The coding strand has the same base sequence as the resulting mRNA.

<p>False</p> Signup and view all the answers

How is RNA synthesized during transcription elongation?

<p>Nucleotides bind to the template strand and are covalently connected in the 5' to 3' direction</p> Signup and view all the answers

What happens during transcription termination?

<p>RNA polymerase reaches a terminator, which causes it and the newly made RNA transcript to dissociate from the DNA</p> Signup and view all the answers

DNA is always transcribed from left to right.

<p>False</p> Signup and view all the answers

Transcription is a complex process that involves different components and stages.

<p>True</p> Signup and view all the answers

The same transcription process and components are used in bacteria and eukaryotes.

<p>False</p> Signup and view all the answers

How many forms of RNA polymerase are present in eukaryotes?

<p>Three forms of RNA polymerase (I, II, and III)</p> Signup and view all the answers

Which RNA polymerase is responsible for transcribing the mRNA from eukaryotic protein-encoding genes?

<p>RNA polymerase II</p> Signup and view all the answers

What do RNA polymerases I and III transcribe?

<p>Genes that specify non-coding RNAs, such as tRNAs and rRNAs</p> Signup and view all the answers

Bacteria have multiple RNA polymerases and sigma factors.

<p>False</p> Signup and view all the answers

The initiation stage of transcription in eukaryotes is simpler than in prokaryotes.

<p>False</p> Signup and view all the answers

What are transcription factors and what is their role in eukaryotic transcription initiation?

<p>Transcription factors are proteins that influence the ability of RNA polymerase to transcribe genes.</p> Signup and view all the answers

What is a preinitiation complex and how is it formed?

<p>The preinitiation complex is formed by the assembly of RNA polymerase II and five transcription factors at the promoter.</p> Signup and view all the answers

What modifications do eukaryotic mRNA transcripts undergo to become functional?

<p>Eukaryotic mRNA transcripts undergo capping, tailing, and splicing.</p> Signup and view all the answers

What does the term "pre-mRNA" refer to?

<p>The initial, longer RNA transcript that is produced before undergoing modifications</p> Signup and view all the answers

What is the name given to the final, modified RNA product?

<p>Mature mRNA (mRNA)</p> Signup and view all the answers

What are the two modifications that are made to the ends of pre-mRNA?

<p>Capping and tailing</p> Signup and view all the answers

What is splicing and what does it involve?

<p>Splicing is the removal of internal segments called introns from the pre-mRNA molecule.</p> Signup and view all the answers

Where does the mature mRNA leave the nucleus?

<p>It leaves the nucleus and enters the cytosol, where translation occurs</p> Signup and view all the answers

What is capping and what is its purpose?

<p>Capping is the covalent attachment of a modified form of guanine at the 5' end of pre-mRNA.</p> Signup and view all the answers

When does capping occur?

<p>While the pre-mRNA is being made by RNA polymerase, usually when the transcript is only 20-25 nucleotides in length.</p> Signup and view all the answers

What are two functions of the 5' cap?

<p>It is recognized by cap-binding proteins, which are needed for the proper exit of mRNAs from the nucleus, and it helps to prevent mRNA degradation in the cytosol.</p> Signup and view all the answers

The 5' cap is crucial for the stability of mRNA.

<p>True</p> Signup and view all the answers

Study Notes

Gene Expression at the Molecular Level: mRNA and Protein Production

  • Gene expression influences cell structure and function, determining organism traits.
  • Gene expression involves three steps: creating an RNA molecule from a gene, modifying the RNA (in eukaryotes), and using RNA to make a protein.
  • Protein-encoding genes are those whose expression results in polypeptides.
  • Mutations, changes in genetic material, can affect gene function, revealing molecular gene function.
  • Gene function can be examined at two levels: molecular function of the protein product, and the organism's trait conferred by the gene.
  • The original "one-gene, one-enzyme" hypothesis is now understood as "one-gene, one-polypeptide."
    • Some proteins are composed of multiple polypeptides, requiring information from multiple genes.
    • Polypeptide refers to amino acid structure; protein refers to function.
  • A single gene can produce multiple polypeptides through alternative mRNA splicing.
  • Non-coding RNA genes produce RNA molecules that aren't translated into proteins.

Central Dogma of Molecular Biology

  • The general dogma is DNA → RNA → Protein, representing transcription and translation.
  • Transcription produces an RNA copy (transcript) of a gene's DNA sequence; mRNA carries this information to ribosomes for translation.
  • Translation synthesizes polypeptides (specific sequences of amino acids) on ribosomes using mRNA as a template.
  • Some genes encode structural RNA (like tRNA and rRNA) not directly translated into polypeptides. Other genes may encode regulatory RNA to control gene expression.
  • While fundamental to both prokaryotes and eukaryotes, eukaryotic gene expression has a crucial additional step of RNA processing.

Eukaryotic Transcription

  • Eukaryotic transcription (DNA to RNA) is more complicated, involving multiple RNA polymerases (I, II, III).
  • RNA polymerase II is a key enzyme for transcribing most protein-encoding genes.
  • RNA polymerases I and III transcribe genes for non-coding RNAs (tRNA, rRNA).
  • In eukaryotes, transcription occurs in the nucleus, and mRNA then moves to the cytoplasm for translation.
  • Eukaryotic mRNA undergoes modifications (capping, tailing, and splicing) within the nucleus before entering the cytoplasm.

RNA Processing

  • Pre-mRNA is the initial transcript before modifications; mature mRNA is the final form.
  • Capping and tailing involve modifications at the ends of the pre-mRNA (5' cap and polyA tail).
  • Splicing removes introns (non-coding segments) to create mature mRNA containing exons (coding segments).
  • Capping protects mRNA and facilitates its export from the nucleus; modification on the end of pre- mRNA.
  • The 5’ cap is a 7-methylguanosine structure crucial for RNA processing.
  • Tailing with the polyA tail is also essential for RNA processing.

Transcription Details

  • Transcription initiation requires recognition of the promoter (start signal) followed by unwinding of the DNA.

  • Transcription elongation involves RNA polymerase sliding along the template DNA strand.

  • Transcription termination occurs at a terminator sequence and triggers the release of RNA polymerase and the newly synthesized mRNA.

  • Promoters, terminators, and regulatory sequences govern the transcription process.

General Features of Genes and Protein-Encoding Genes

  • Genes are functional units of DNA, transcribed into RNA and producing specific protein products.
  • Genes control the characteristics of an organism based on their protein products.
  • All organisms use the basic transcription process, although the exact details can differ between species.
  • In contrast to the basic process (DNA>RNA>Protein), some viruses use RNA as a template to synthesize DNA.

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Description

This quiz explores gene expression at the molecular level, focusing on the processes of mRNA creation, protein synthesis, and the impact of mutations. It covers concepts such as the 'one-gene, one-polypeptide' hypothesis and the relationship between gene function and organism traits. Test your knowledge of how genes influence cell structure and function.

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