DNA Transcription Overview
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Questions and Answers

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

  • To synthesize a complementary RNA strand from the DNA template (correct)
  • To translate RNA sequence into a protein sequence
  • To release the newly synthesized RNA molecule
  • To unwind the DNA strands

    • In which direction does RNA polymerase read the DNA template strand during transcription?

  • 5' to 3'
  • 3' to 5' (correct)
  • Left to right
  • Right to left

    • What is the result of the initiation stage of transcription?

  • Unwinding of the DNA strands (correct)
  • Formation of a protein sequence
  • Synthesis of a complementary RNA strand
  • Release of the newly synthesized RNA molecule

    • What is the relationship between the DNA coding strand and the RNA sequence?

    <p>The DNA coding strand has the same sequence as the RNA</p> Signup and view all the answers

    What is the role of the promoter region in transcription?

    <p>To initiate transcription by binding RNA polymerase</p> Signup and view all the answers

    What is the direction of RNA synthesis during transcription?

    <p>5' to 3'</p> Signup and view all the answers

    What is the result of the termination stage of transcription?

    <p>Release of the newly synthesized RNA molecule</p> Signup and view all the answers

    What is the relationship between the DNA template strand and the RNA sequence?

    <p>The DNA template strand is complementary to the RNA</p> Signup and view all the answers

    What is the role of RNA polymerase in transcription?

    <p>To catalyze the formation of phosphodiester bonds</p> Signup and view all the answers

    What is the function of the σ subunit in RNA polymerase?

    <p>To recognize the promoter site</p> Signup and view all the answers

    What marks the beginning and end of the DNA segment to be transcribed?

    <p>Specific sequences</p> Signup and view all the answers

    What is the direction of RNA synthesis during transcription?

    <p>5' to 3'</p> Signup and view all the answers

    What is the purpose of the terminator sequence in transcription?

    <p>To terminate transcription</p> Signup and view all the answers

    What is the role of the coding strand in DNA transcription?

    <p>To serve as the coding strand</p> Signup and view all the answers

    What are the building blocks of RNA synthesis?

    <p>Nucleoside triphosphates (NTPs)</p> Signup and view all the answers

    What is the structure of RNA polymerase?

    <p>Multimeric enzyme</p> Signup and view all the answers

    What is the function of the β subunit in RNA polymerase?

    <p>To catalyze the formation of phosphodiester bonds</p> Signup and view all the answers

    What is the purpose of the α subunits in RNA polymerase?

    <p>To determine the DNA to be transcribed</p> Signup and view all the answers

    What is the purpose of the RNA polymerase binding to the promoter region?

    <p>To initiate transcription</p> Signup and view all the answers

    What is the direction of the DNA sequence read by RNA polymerase?

    <p>3' to 5'</p> Signup and view all the answers

    What is synthesized during the elongation stage of transcription?

    <p>A complementary RNA strand</p> Signup and view all the answers

    What corresponds to a specific amino acid in mRNA?

    <p>A set of three nucleotides</p> Signup and view all the answers

    What is the result of the transcription process?

    <p>A single-stranded RNA</p> Signup and view all the answers

    What is the function of the template strand in DNA transcription?

    <p>To serve as a template for RNA synthesis</p> Signup and view all the answers

    What is the direction of RNA synthesis?

    <p>5' to 3'</p> Signup and view all the answers

    What replaces T in RNA?

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

    What is the main difference between DNA replication and transcription?

    <p>DNA replication involves the entire DNA molecule, while transcription only involves a particular gene.</p> Signup and view all the answers

    What is the function of the terminator sequence in transcription?

    <p>To terminate transcription</p> Signup and view all the answers

    What is the purpose of the promoter region in transcription?

    <p>To bind RNA polymerase to initiate transcription</p> Signup and view all the answers

    What is the orientation of the RNA transcript relative to the DNA template strand?

    <p>The RNA transcript is synthesized in the 5' to 3' direction</p> Signup and view all the answers

    What is the function of the β' subunit in RNA polymerase?

    <p>To bind and open the DNA template</p> Signup and view all the answers

    What is the role of the coding strand in DNA transcription?

    <p>It contains the gene to be transcribed into RNA</p> Signup and view all the answers

    What is the purpose of the UP element in transcription?

    <p>To interact with the α subunits</p> Signup and view all the answers

    What is the function of the ω subunit in RNA polymerase?

    <p>Its function is not known</p> Signup and view all the answers

    What is the significance of the primary transcript in transcription?

    <p>It is the precursor to the functional RNA molecule</p> Signup and view all the answers

    What is the result of RNA polymerase binding to the promoter region?

    <p>The DNA template strand is unwound</p> Signup and view all the answers

    What happens when RNA polymerase reaches the terminator sequence on the DNA?

    <p>It releases the pre-mRNA and reforms the DNA double helix</p> Signup and view all the answers

    What is the role of the recognition sites on the DNA?

    <p>To bind RNA polymerase and initiate transcription</p> Signup and view all the answers

    What is the direction of pre-mRNA synthesis during elongation?

    <p>5' to 3'</p> Signup and view all the answers

    What is the significance of the open complex in transcription?

    <p>It is the unwound DNA region ready for transcription to start</p> Signup and view all the answers

    What is unique about the RNA synthesized during transcription?

    <p>It contains uracil</p> Signup and view all the answers

    What is the result of the unwinding of the DNA double helix during initiation?

    <p>The formation of the open complex</p> Signup and view all the answers

    What is the outcome of the interaction between RNA polymerase and the promoter region on the DNA?

    <p>Formation of a closed complex</p> Signup and view all the answers

    What is the role of the -35 and -10 regions in transcription?

    <p>To direct RNA polymerase to the promoter region</p> Signup and view all the answers

    What occurs during the formation of an open complex in transcription?

    <p>The DNA double helix unwinds</p> Signup and view all the answers

    What is the function of transcription factors in transcription?

    <p>To mediate the binding of RNA polymerase to the DNA</p> Signup and view all the answers

    What is the result of the release of the σ factor from the transcriptional complex?

    <p>Continuation of RNA synthesis by the core enzyme</p> Signup and view all the answers

    In which direction are nucleotides added to the growing RNA strand during elongation?

    <p>5' to 3'</p> Signup and view all the answers

    What is the function of the promoter elements, such as the TATA box and the -35 sequence?

    <p>To direct RNA polymerase to the start of transcription</p> Signup and view all the answers

    What is the outcome of RNA polymerase moving along the template strand during elongation?

    <p>The RNA strand gets longer</p> Signup and view all the answers

    What is the typical first nucleotide in an RNA transcript?

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

    What is the energy source for phosphodiester bond formation?

    <p>Hydrolysis of ATP</p> Signup and view all the answers

    What is the purpose of the σ factor during elongation?

    <p>To bind to promoter regions</p> Signup and view all the answers

    What is the result of rho-dependent termination?

    <p>RNA polymerase dissociates from DNA</p> Signup and view all the answers

    What is the purpose of the palindromic G-C rich region in rho-independent termination?

    <p>To form a hairpin loop structure</p> Signup and view all the answers

    What is the role of pyrophosphatase in transcription?

    <p>To ensure the reaction is energetically favorable</p> Signup and view all the answers

    What is the composition of the core enzyme of RNA polymerase?

    <p>α, β, β', ω</p> Signup and view all the answers

    What is the function of the rho factor in transcription?

    <p>To unwind the DNA-RNA hybrid</p> Signup and view all the answers

    What is the region of unwound DNA called during transcription?

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

    What is the result of phosphodiester bond formation?

    <p>The formation of a 3' to 5' phosphodiester bond</p> Signup and view all the answers

    What is the purpose of the -35 sequence and the TATA box in transcription?

    <p>To direct RNA polymerase to initiate transcription</p> Signup and view all the answers

    What happens to the DNA helix during the initiation stage of transcription?

    <p>It unwinds</p> Signup and view all the answers

    What is released from the transcriptional complex during elongation?

    <p>The σ factor</p> Signup and view all the answers

    What is the result of the formation of an open complex in transcription?

    <p>The template strand is exposed</p> Signup and view all the answers

    What is the function of transcription factors in transcription?

    <p>To mediate the binding of RNA polymerase to the DNA</p> Signup and view all the answers

    What is the direction of RNA synthesis during elongation?

    <p>5' to 3'</p> Signup and view all the answers

    What is the role of the closed complex in transcription?

    <p>To form a complex between RNA polymerase and the promoter region</p> Signup and view all the answers

    What is the outcome of RNA polymerase binding to the promoter region?

    <p>The formation of a closed complex occurs</p> Signup and view all the answers

    What is the primary function of the recognition sites on the DNA?

    <p>To bind RNA polymerase to the promoter region</p> Signup and view all the answers

    What is the consequence of the weak A-U bonds during transcription?

    <p>The RNA polymerase stops and releases from the DNA</p> Signup and view all the answers

    What is the direction of the template strand being read by RNA polymerase during elongation?

    <p>3' to 5'</p> Signup and view all the answers

    What is the result of the formation of an open complex during initiation?

    <p>The template strand is ready to be read</p> Signup and view all the answers

    What is unique about the RNA synthesized during transcription?

    <p>It contains the base uracil instead of thymine</p> Signup and view all the answers

    What happens to the DNA double helix during initiation?

    <p>It is temporarily unwound to form the open complex</p> Signup and view all the answers

    What is the usual first nucleotide in an RNA transcript?

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

    What is the complex of RNA polymerase, DNA template, and new RNA transcript called?

    <p>Ternary complex</p> Signup and view all the answers

    What type of bond is formed between nucleotides during transcription?

    <p>Phosphodiester bond</p> Signup and view all the answers

    What provides the energy required for phosphodiester bond formation?

    <p>Hydrolysis of nucleoside triphosphates</p> Signup and view all the answers

    What is the outcome when RNA polymerase reaches a terminator sequence on the DNA?

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

    What is the function of the rho factor in rho-dependent termination?

    <p>To unwind the DNA-RNA hybrid</p> Signup and view all the answers

    What is the characteristic of rho-independent terminators?

    <p>They have a palindromic G-C rich region</p> Signup and view all the answers

    What is the outcome of the release of pyrophosphate during phosphodiester bond formation?

    <p>Energy is released</p> Signup and view all the answers

    What is the function of the σ factor during transcription?

    <p>To recognize the promoter region</p> Signup and view all the answers

    What is the result of the formation of a hairpin loop structure in the RNA transcript?

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

    What is the primary function of the 5' cap in mRNA?

    <p>To increase the stability of the mRNA</p> Signup and view all the answers

    What is the result of polyadenylation?

    <p>Addition of a chain of adenylate residues to the 3' end of mRNA</p> Signup and view all the answers

    What are introns?

    <p>Non-coding sequences that do not encode functional proteins</p> Signup and view all the answers

    What is the purpose of splicing?

    <p>To remove introns and join exons together</p> Signup and view all the answers

    What is the role of poly-A binding protein II?

    <p>To bind to the newly added poly-A tail</p> Signup and view all the answers

    What is the result of capping?

    <p>Attachment of a 7-methylguanosine to the 5' end of mRNA</p> Signup and view all the answers

    What is the primary function of RNA processing?

    <p>To stabilize and protect RNA for function in the cytosol</p> Signup and view all the answers

    What is the result of RNA processing in the nucleus?

    <p>Mature mRNA is transported to the cytosol</p> Signup and view all the answers

    Study Notes

    DNA Transcription Overview

    • DNA transcription is the process of synthesizing RNA from a DNA template using the enzyme RNA polymerase.

    Stages of Transcription

    • Initiation: RNA polymerase binds to a specific DNA sequence called the promoter, initiating DNA unwinding.
    • Elongation: RNA polymerase moves along the template strand, synthesizing a complementary RNA strand in the 5' to 3' direction.
    • Termination: RNA polymerase releases the RNA molecule when it reaches a termination signal, and the DNA helix re-forms.

    DNA to RNA Transcription

    • The DNA sequence is used as a template to synthesize the RNA sequence.
    • The RNA sequence is complementary to the DNA template strand.
    • The DNA coding strand has the same sequence as the RNA (except T is replaced with U in RNA).

    Translation

    • The RNA sequence (mRNA) is translated into a protein sequence.
    • Each set of three nucleotides (codon) in mRNA corresponds to a specific amino acid.

    Base Sequence

    • dsDNA: The double-stranded DNA (dsDNA) serves as the template for transcription, consisting of a template strand and a non-template strand.
    • sRNA: The RNA polymerase synthesizes a single-stranded RNA (sRNA) from the template strand of DNA in the 5' to 3' direction.

    Direction of Synthesis

    • RNA polymerase reads the template strand from 3' to 5' and synthesizes the RNA in the 5' to 3' direction.

    Promoter Region

    • The promoter region is where RNA polymerase binds to initiate transcription, located upstream of the transcription start site.

    Features of Transcription

    • Highly Selective: Transcription is highly selective due to signals embedded in the nucleotide sequence of DNA.
    • RNA Transcripts: Many RNA transcripts are synthesized as precursors known as primary transcripts, which are modified and trimmed to become functional RNA.

    Differences in DNA Replication and Transcription

    • Replication: The entire DNA molecule is normally copied.
    • Transcription: Only a particular gene is copied at any time, and some portions of DNA are never transcribed.

    Gene Identification

    • Specific regions (genes) on the DNA are marked and highlighted as the focus for transcription.

    RNA Polymerase Role

    • RNA polymerase is the main enzyme involved in transcription, binding to the DNA at the promoter region to initiate transcription.

    Detailed Process of Transcription

    • Initiation: Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene, unwinding the DNA and starting RNA synthesis.
    • Elongation: RNA polymerase moves along the template strand, adding nucleotides to the growing RNA transcript in the 5' to 3' direction.
    • Termination: The process continues until RNA polymerase reaches a terminator sequence on the DNA, releasing the RNA transcript and re-annealing the DNA strands.

    Key Components in Transcription Diagrams

    • Promoter: The region where RNA polymerase binds to start transcription.
    • Coding Sequence: The portion of the DNA that is transcribed into RNA.
    • Terminator: The sequence that signals the end of transcription.
    • NTPs: The building blocks that are added to the growing RNA chain.

    Transcription Process Details

    • RNA Polymerase and Promoter: Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene, moving along the DNA template strand and synthesizing RNA in the 5' to 3' direction.
    • Coding Sequence: The coding sequence of the DNA contains the gene to be transcribed into RNA.
    • Terminator Sequence: Transcription ends when RNA polymerase reaches a terminator sequence on the DNA.

    DNA Transcription Strand with Gene

    • Coding Strand (+sense): This strand contains the gene and has the same sequence as the RNA transcript (except T is replaced by U).
    • Template Strand (Antisense): This is the complementary strand that is transcribed.

    RNA Synthesis

    • The RNA strand is synthesized using the template strand.

    RNA Polymerase Structure and Functions

    • Multimeric Enzyme: Consists of six subunits: 2α, β, β', ω, and σ.
    • Functions: Searches for and binds to the promoter site, unwinds DNA, selects the correct ribonucleotide, catalyzes phosphodiester bond formation, detects signals for transcription termination, and interacts with activator and repressor proteins.

    RNA Polymerase Subunits and Functions

    • α, α: Determine the DNA to be transcribed.
    • β: Catalyzes polymerization.
    • β': Binds and opens the DNA template.
    • ω: Function is not known.
    • σ: Recognizes the initiation sites called the promoter.

    Types of RNA Polymerase and Their Functions

    • RNA Polymerase I: Synthesizes the precursor of the larger ribosomal RNAs.
    • RNA Polymerase II: Synthesizes the precursor of the mRNA and certain small nuclear RNAs.
    • RNA Polymerase III: Produces the small RNAs, including tRNA.

    DNA Transcription Overview

    • DNA transcription is the process of synthesizing RNA from a DNA template using the enzyme RNA polymerase.

    Stages of Transcription

    • Initiation: RNA polymerase binds to a specific DNA sequence called the promoter, initiating DNA unwinding.
    • Elongation: RNA polymerase moves along the template strand, synthesizing a complementary RNA strand in the 5' to 3' direction.
    • Termination: RNA polymerase releases the RNA molecule when it reaches a termination signal, and the DNA helix re-forms.

    DNA to RNA Transcription

    • The DNA sequence is used as a template to synthesize the RNA sequence.
    • The RNA sequence is complementary to the DNA template strand.
    • The DNA coding strand has the same sequence as the RNA (except T is replaced with U in RNA).

    Translation

    • The RNA sequence (mRNA) is translated into a protein sequence.
    • Each set of three nucleotides (codon) in mRNA corresponds to a specific amino acid.

    Base Sequence

    • dsDNA: The double-stranded DNA (dsDNA) serves as the template for transcription, consisting of a template strand and a non-template strand.
    • sRNA: The RNA polymerase synthesizes a single-stranded RNA (sRNA) from the template strand of DNA in the 5' to 3' direction.

    Direction of Synthesis

    • RNA polymerase reads the template strand from 3' to 5' and synthesizes the RNA in the 5' to 3' direction.

    Promoter Region

    • The promoter region is where RNA polymerase binds to initiate transcription, located upstream of the transcription start site.

    Features of Transcription

    • Highly Selective: Transcription is highly selective due to signals embedded in the nucleotide sequence of DNA.
    • RNA Transcripts: Many RNA transcripts are synthesized as precursors known as primary transcripts, which are modified and trimmed to become functional RNA.

    Differences in DNA Replication and Transcription

    • Replication: The entire DNA molecule is normally copied.
    • Transcription: Only a particular gene is copied at any time, and some portions of DNA are never transcribed.

    Gene Identification

    • Specific regions (genes) on the DNA are marked and highlighted as the focus for transcription.

    RNA Polymerase Role

    • RNA polymerase is the main enzyme involved in transcription, binding to the DNA at the promoter region to initiate transcription.

    Detailed Process of Transcription

    • Initiation: Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene, unwinding the DNA and starting RNA synthesis.
    • Elongation: RNA polymerase moves along the template strand, adding nucleotides to the growing RNA transcript in the 5' to 3' direction.
    • Termination: The process continues until RNA polymerase reaches a terminator sequence on the DNA, releasing the RNA transcript and re-annealing the DNA strands.

    Key Components in Transcription Diagrams

    • Promoter: The region where RNA polymerase binds to start transcription.
    • Coding Sequence: The portion of the DNA that is transcribed into RNA.
    • Terminator: The sequence that signals the end of transcription.
    • NTPs: The building blocks that are added to the growing RNA chain.

    Transcription Process Details

    • RNA Polymerase and Promoter: Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene, moving along the DNA template strand and synthesizing RNA in the 5' to 3' direction.
    • Coding Sequence: The coding sequence of the DNA contains the gene to be transcribed into RNA.
    • Terminator Sequence: Transcription ends when RNA polymerase reaches a terminator sequence on the DNA.

    DNA Transcription Strand with Gene

    • Coding Strand (+sense): This strand contains the gene and has the same sequence as the RNA transcript (except T is replaced by U).
    • Template Strand (Antisense): This is the complementary strand that is transcribed.

    RNA Synthesis

    • The RNA strand is synthesized using the template strand.

    RNA Polymerase Structure and Functions

    • Multimeric Enzyme: Consists of six subunits: 2α, β, β', ω, and σ.
    • Functions: Searches for and binds to the promoter site, unwinds DNA, selects the correct ribonucleotide, catalyzes phosphodiester bond formation, detects signals for transcription termination, and interacts with activator and repressor proteins.

    RNA Polymerase Subunits and Functions

    • α, α: Determine the DNA to be transcribed.
    • β: Catalyzes polymerization.
    • β': Binds and opens the DNA template.
    • ω: Function is not known.
    • σ: Recognizes the initiation sites called the promoter.

    Types of RNA Polymerase and Their Functions

    • RNA Polymerase I: Synthesizes the precursor of the larger ribosomal RNAs.
    • RNA Polymerase II: Synthesizes the precursor of the mRNA and certain small nuclear RNAs.
    • RNA Polymerase III: Produces the small RNAs, including tRNA.

    Transcription Stages

    Initiation

    • RNA polymerase recognizes and binds to the promoter region on the DNA, causing the DNA helix to unwind and exposing the template strand.
    • Promoter sequences, including the TATA box and -35 sequence, direct RNA polymerase to initiate transcription.
    • Transcription factors mediate the binding of RNA polymerase to the DNA.
    • RNA polymerase forms a closed complex, which then unwinds to form an open complex, allowing RNA polymerase to access the template strand.

    Elongation

    • RNA polymerase moves along the template strand, reading the DNA and synthesizing the RNA strand in the 5' to 3' direction.
    • Nucleotides are added to the growing RNA strand, with the first nucleotide usually being pppG or pppA.
    • The σ factor is released from the transcriptional complex, leaving the core enzyme to continue the elongation of the RNA transcript.
    • Phosphodiester bonds are formed through the reaction of the 3'-OH group of one nucleotide with the 5' triphosphate of a second nucleotide.
    • Energy from the hydrolysis of nucleoside triphosphates (e.g., ATP, GTP) drives the formation of phosphodiester bonds.

    Termination

    • Transcription ends when RNA polymerase reaches a terminator sequence on the DNA, releasing the RNA transcript and allowing the DNA helix to re-form.
    • Termination is signaled by a specific sequence in the template strand of the DNA.
    • The rho factor recognizes termination signals on the RNA and prevents RNA polymerase from moving further along the DNA, causing it to dissociate from the DNA.
    • In rho-independent termination, a palindromic G-C rich region forms a hairpin structure in the RNA transcript, causing RNA polymerase to pause and release the RNA transcript.

    Eukaryotic Transcription

    Initiation

    • RNA polymerase recognizes recognition sites on the DNA and binds to the promoter region, signaling the start of a gene.
    • RNA polymerase separates the DNA into single strands, allowing the template strand to be read in the 3' to 5' direction.

    Elongation

    • Pre-mRNA nucleotides are quickly paired with their complementary bases on the template strand of DNA.
    • The pre-mRNA is synthesized in the 5' to 3' direction, while the template strand is read in the 3' to 5' direction.
    • Uracil is used as the complementary base for adenine in pre-mRNA.

    Termination

    • When RNA polymerase reaches the terminator sequence on the DNA, it signals RNA polymerase to stop and release from the DNA.
    • The newly synthesized pre-mRNA is then released.

    Transcription Stages

    Initiation

    • RNA polymerase recognizes and binds to the promoter region on the DNA, causing the DNA helix to unwind and exposing the template strand.
    • Promoter sequences, including the TATA box and -35 sequence, direct RNA polymerase to initiate transcription.
    • Transcription factors mediate the binding of RNA polymerase to the DNA.
    • RNA polymerase forms a closed complex, which then unwinds to form an open complex, allowing RNA polymerase to access the template strand.

    Elongation

    • RNA polymerase moves along the template strand, reading the DNA and synthesizing the RNA strand in the 5' to 3' direction.
    • Nucleotides are added to the growing RNA strand, with the first nucleotide usually being pppG or pppA.
    • The σ factor is released from the transcriptional complex, leaving the core enzyme to continue the elongation of the RNA transcript.
    • Phosphodiester bonds are formed through the reaction of the 3'-OH group of one nucleotide with the 5' triphosphate of a second nucleotide.
    • Energy from the hydrolysis of nucleoside triphosphates (e.g., ATP, GTP) drives the formation of phosphodiester bonds.

    Termination

    • Transcription ends when RNA polymerase reaches a terminator sequence on the DNA, releasing the RNA transcript and allowing the DNA helix to re-form.
    • Termination is signaled by a specific sequence in the template strand of the DNA.
    • The rho factor recognizes termination signals on the RNA and prevents RNA polymerase from moving further along the DNA, causing it to dissociate from the DNA.
    • In rho-independent termination, a palindromic G-C rich region forms a hairpin structure in the RNA transcript, causing RNA polymerase to pause and release the RNA transcript.

    Eukaryotic Transcription

    Initiation

    • RNA polymerase recognizes recognition sites on the DNA and binds to the promoter region, signaling the start of a gene.
    • RNA polymerase separates the DNA into single strands, allowing the template strand to be read in the 3' to 5' direction.

    Elongation

    • Pre-mRNA nucleotides are quickly paired with their complementary bases on the template strand of DNA.
    • The pre-mRNA is synthesized in the 5' to 3' direction, while the template strand is read in the 3' to 5' direction.
    • Uracil is used as the complementary base for adenine in pre-mRNA.

    Termination

    • When RNA polymerase reaches the terminator sequence on the DNA, it signals RNA polymerase to stop and release from the DNA.
    • The newly synthesized pre-mRNA is then released.

    RNA Processing

    • Most eukaryotic RNA must be processed before becoming fully functional to stabilize and protect it for functioning in the cytosol and regulating gene expression.

    Formation of Mature mRNA

    • Mature mRNA is formed by modifying the primary transcript (heterogeneous nuclear RNA or hRNA) through three major modifications:
    • 5' Capping:
      • A 7-methylguanosine is attached to the 5'-terminal end of the mRNA through a triphosphate bridge.
      • The cap structure is crucial for mRNA stability and initiation of translation.
    • 3' Polyadenylation:
      • A chain of adenylate residues (poly-A tail) is added to the 3' terminus of the mRNA.
      • The poly-A tail increases mRNA stability and facilitates export from the nucleus to the cytoplasm.
    • Pre-mRNA Splicing:
      • Exons are protein-coding sequences, whereas introns are non-coding sequences.
      • During splicing, introns are removed, and exons are joined together to form the final spliced mRNA.

    Pre-mRNA Splicing Process

    • Spliceosomes, composed of small nuclear ribonucleoproteins (snRNPs), recognize splice sites at the ends of introns.
    • The spliceosome removes the intron, joining the exons together.
    • The resulting mature mRNA contains a continuous sequence of exons, ready for translation into a protein.

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    Description

    Learn about the process of DNA transcription, including its stages of initiation, elongation, and termination. Understand how RNA polymerase synthesizes RNA from a DNA template.

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