Biology Transcription Process
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Questions and Answers

What is the first step a cell takes in reading out its genetic instructions?

To copy a particular portion of its DNA nucleotide sequence-a gene-into an RNA nucleotide sequence.

What is the name given to the process of copying DNA into RNA?

Transcription.

The information in RNA is written in a different language than DNA.

False (B)

Transcription produces RNA that is identical to the DNA strand it is copied from.

<p>False (B)</p> Signup and view all the answers

What is the name of the enzyme that performs transcription?

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

RNA polymerase requires a primer to initiate transcription.

<p>False (B)</p> Signup and view all the answers

Which of the following statements is NOT true about RNA polymerase?

<p>RNA polymerase is more accurate than DNA polymerase. (B)</p> Signup and view all the answers

The RNA strand produced during transcription remains bound to the DNA template strand.

<p>False (B)</p> Signup and view all the answers

What is the term for a transcribed segment of DNA?

<p>Transcription unit.</p> Signup and view all the answers

What is the main difference between transcription in bacteria and eukaryotes?

<p>Bacteria use a single RNA polymerase, while eukaryotes use multiple. (D)</p> Signup and view all the answers

What is the name of the detachable subunit of bacterial RNA polymerase that helps it recognize the start site for transcription?

<p>Sigma (σ) factor.</p> Signup and view all the answers

RNA polymerase binds very tightly to the promoter DNA before initiating transcription.

<p>True (A)</p> Signup and view all the answers

What is the name of the DNA sequence that signals the end of transcription?

<p>Terminator.</p> Signup and view all the answers

Transcription termination involves a reversible structural change in the RNA polymerase.

<p>True (A)</p> Signup and view all the answers

What is the main purpose of promoter sequences in DNA?

<p>To provide a binding site for RNA polymerase. (D)</p> Signup and view all the answers

Promoter sequences are symmetrical.

<p>False (B)</p> Signup and view all the answers

What is the main consequence of the asymmetry of promoter sequences?

<p>Each gene typically has a single promoter, and transcription occurs in only one direction.</p> Signup and view all the answers

The choice of template strand for transcription is determined by the location of the promoter.

<p>True (A)</p> Signup and view all the answers

Flashcards

Transcription

The process of making RNA from DNA, a crucial first step in gene expression.

RNA (Ribonucleic Acid)

The molecule transcribed from DNA, carrying genetic information to be translated into a protein.

Gene

A segment of DNA that contains the genetic instructions for building a specific protein, serving as the template for transcription.

Promoter

A specific DNA sequence near the beginning of a gene, telling RNA polymerase where to start transcribing.

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Terminator

A specific DNA sequence at the end of a gene, signaling RNA polymerase to stop transcription.

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RNA Polymerase

The enzyme responsible for catalyzing the synthesis of RNA from a DNA template.

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Sigma (σ) Factor

A detachable subunit of bacterial RNA polymerase that helps the enzyme locate promoters, making it efficient at finding the start of genes.

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DNA Unwinding

The process where the RNA polymerase opens up the DNA double helix to access the template strand.

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RNA Chain Elongation

The process of adding ribonucleotides one by one to the growing RNA molecule, creating a complementary copy of the DNA template.

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Hairpin Structure

A special structure formed by the newly synthesized RNA transcript, which helps terminate transcription in bacteria, sometimes likened to a 'hairpin' structure.

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Transcript

The final, newly synthesized RNA molecule produced after transcription is complete.

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mRNA (Messenger RNA)

The type of RNA that carries the genetic code from DNA to the ribosomes for protein synthesis.

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rRNA (Ribosomal RNA)

RNA molecules that make up the structural core of ribosomes, the protein-making machinery of the cell.

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tRNA (Transfer RNA)

Small RNA molecules that act as adaptors, bringing amino acids to the ribosome for protein synthesis.

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Translation

The process of translating the genetic code carried by mRNA into a sequence of amino acids, forming a protein.

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Genome

A complete set of genetic instructions in an organism or cell, encompassing all its DNA.

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DNA Replication

The process of copying DNA into a new strand of DNA, ensuring that genetic information is passed on accurately during cell division.

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Origin of Replication

The specific region of a chromosome where DNA replication starts.

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DNA Polymerase

The enzyme that catalyzes DNA replication, adding nucleotides to a new DNA strand, using an existing strand as a template.

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Primer

A short stretch of RNA that provides a starting point for DNA polymerase to begin DNA replication.

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Transcription

The process of copying DNA into RNA, the first step in gene expression, where RNA polymerase synthesizes a molecule of RNA using a DNA template.

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Translation

The process of translating the genetic code carried by mRNA into a sequence of amino acids, forming a protein, which is the final product of gene expression.

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Transcription Factor

A molecule that binds to DNA and influences the rate of transcription, regulating gene expression.

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Operon

A group of genes that are transcribed together as a single unit, often found in bacteria.

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Translation

The process of decoding the genetic code carried by mRNA into a sequence of amino acids, forming a protein, which is the final product of gene expression.

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Codon

A set of three consecutive nucleotides in mRNA that codes for a specific amino acid during protein synthesis.

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Alternative Splicing

The process by which a single gene can produce multiple proteins.

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Regulatory Sequence

A specific region of the DNA sequence that controls whether a gene is expressed or not.

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Study Notes

Transcription: From DNA to RNA

  • Transcription is the first step in a cell reading genetic instructions
  • A portion of DNA (a gene) is copied into RNA
  • The copied information in RNA uses the same language as DNA (nucleotides)
  • The process copies a specific portion of a DNA nucleotide sequence known as a gene
  • RNA carries the information to synthesize proteins

Transcription Produces RNA Complementary to One Strand of DNA

  • RNA synthesis is similar to DNA replication (unwinding of a portion of DNA double helix)
  • The process exposes bases on each DNA strand, then one strand of DNA serves as a template for RNA synthesis
  • The RNA produced is complementary to the DNA template strand
  • RNA is shorter than DNA
  • The RNA polymerase, an enzyme, catalyzes the bonding of nucleotides in RNA
  • RNA polymerase moves along the DNA, separating the DNA strands
  • It adds new RNA nucleotides to the growing RNA chain (synthesis in 5' to 3' direction).
  • RNA strand does not remain hydrogen-bonded to DNA template strand
  • RNA is released as a single strand

Differences Between DNA and RNA Polymerases

  • RNA polymerase doesn't require a primer to start RNA synthesis
  • RNA polymerase is less accurate than DNA polymerase (about one mistake for every 10,000 nucleotides compared to 10 million for DNA).
  • RNA polymerase has a modest proofreading mechanism
  • RNA polymerase links ribonucleotides (not deoxyribonucleotides)

Cells Produce Several Types of RNA

  • Different types of RNA are produced for various functions (messenger RNA, ribosomal RNA, transfer RNA, small nuclear RNA, small nucleolar RNA, microRNA, other noncoding RNAs)
  • Each transcribed segment of DNA is a transcription unit
  • In eukaryotes, a transcription unit typically carries the information for a single gene
  • In bacteria, a set of adjacent genes can be transcribed as a unit

Signals Encoded in DNA

  • RNA polymerase must recognize start and stop points in the DNA sequence to transcribe a gene accurately
  • The way RNA polymerase performs varies between bacteria and eukaryotes.

Steps of Transcription in Bacteria

  • RNA polymerase binds tightly to a specific sequence in the DNA called a promoter
  • The polymerase opens the DNA helix to expose a short stretch of nucleotides
  • It utilizes one of the two exposed DNA strands as a template
  • The polymerase adds incoming ribonucleotides, constructing an RNA chain in the 5' to 3' direction
  • The σ factor in the RNA polymerase dissociates as RNA synthesis continues
  • The polymerase encounters a termination signal
  • At the termination signal, the RNA strand detaches from DNA; RNA polymerase releases the DNA template.

Promoter Sequences

  • Promoter sequences are asymmetrical in DNA
  • They determine which DNA strand is used as a template for RNA synthesis
  • The polymerase can only bind in one orientation in a specific location
  • The direction of transcription is determined by the promoter location, and it proceeds in the 5'→3' direction.

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Description

This quiz explores the process of transcription, where DNA is copied into RNA, the essential step in gene expression. It covers the mechanisms involved in RNA synthesis and how RNA complements one strand of DNA. Test your understanding of this vital biological process and its role in protein synthesis.

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