Lecture 4 Review
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Questions and Answers

What is the primary function of RNA polymerase during transcription?

  • To replicate DNA for cell division
  • To synthesize RNA from a DNA template (correct)
  • To translate RNA into proteins
  • To splice RNA molecules

    • Which strand of DNA is used as the template for synthesizing RNA during transcription?

  • Lagging strand
  • Anti-sense strand
  • Template strand (correct)
  • Coding strand

    • Why does the RNA sequence produced during transcription differ from the DNA coding strand?

  • The RNA sequence is synthesized from proteins
  • The RNA sequence is double-stranded
  • The RNA sequence incorporates uracil instead of thymine (correct)
  • The RNA sequence is synthesized in the 3’ to 5’ direction

    • What percentage of the human genome consists of protein-coding genes?

    <p>1% (C)</p> Signup and view all the answers

    Which process describes the conversion of DNA instructions into RNA?

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

    What is the primary function of acyl-tRNA synthetases?

    <p>To attach amino acids to the appropriate tRNA (A)</p> Signup and view all the answers

    How many amino acyl-tRNA synthetases are there at a minimum?

    <p>At least one for each amino acid (C)</p> Signup and view all the answers

    What is the role of ribosomal RNA (rRNA) in translation?

    <p>To catalyze peptide bond formation (A)</p> Signup and view all the answers

    What characterizes the 'RNA world' hypothesis in the origin of life?

    <p>RNA can encode genetic information and perform catalytic activities (B)</p> Signup and view all the answers

    What components make up a complete ribosome?

    <p>4 rRNA molecules and 82 proteins (D)</p> Signup and view all the answers

    What are the building blocks of RNA?

    <p>Nucleotides (C)</p> Signup and view all the answers

    Which sugar is used in RNA instead of deoxyribose used in DNA?

    <p>Ribose (C)</p> Signup and view all the answers

    What is the role of phosphodiester linkage in RNA?

    <p>To form polymers of nucleotides (B)</p> Signup and view all the answers

    How are RNA molecules structurally different from DNA?

    <p>RNA has a single-stranded structure (A)</p> Signup and view all the answers

    What type of structures can RNA fold into due to base-pairing?

    <p>Complex 3D structures (A)</p> Signup and view all the answers

    Which nucleotide is found in RNA instead of thymine?

    <p>Uracil (C)</p> Signup and view all the answers

    What process links monomers to form RNA polymers?

    <p>Condensation (D)</p> Signup and view all the answers

    In which cellular location is RNA synthesized?

    <p>Nucleus (D)</p> Signup and view all the answers

    What is the start codon in eukaryotic cells?

    <p>AUG (D)</p> Signup and view all the answers

    How many stop codons exist in the genetic code?

    <p>Three (D)</p> Signup and view all the answers

    In which direction is mRNA translated?

    <p>5’ to 3’ (D)</p> Signup and view all the answers

    What role do amino acyl-tRNA synthetases play in translation?

    <p>They couple the correct amino acid to its tRNA. (A)</p> Signup and view all the answers

    What is the role of the start codon AUG in translation?

    <p>It initiates translation and defines the reading frame. (C)</p> Signup and view all the answers

    What does the anticodon of tRNA do?

    <p>It binds to the corresponding codon on mRNA. (D)</p> Signup and view all the answers

    Which direction do polypeptides get synthesized?

    <p>NH2 to COOH (B)</p> Signup and view all the answers

    What happens when translation reaches a stop codon?

    <p>Release factors bind and terminate translation. (B)</p> Signup and view all the answers

    What is the primary role of the promoter in prokaryotic transcription?

    <p>It determines the template strand and start site for RNA synthesis. (C)</p> Signup and view all the answers

    In which direction does RNA polymerase synthesize RNA?

    <p>5’ to 3’ direction (D)</p> Signup and view all the answers

    How many errors does RNA polymerase typically make in RNA synthesis?

    <p>1 error per 1,000 nucleotides (C)</p> Signup and view all the answers

    Which type of RNA is directly involved in carrying amino acids during protein synthesis?

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

    What distinguishes messenger RNA (mRNA) from other types of RNA?

    <p>It serves as a template for protein synthesis. (A)</p> Signup and view all the answers

    Which enzyme is primarily responsible for synthesizing RNA during transcription?

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

    What type of RNA is predominantly involved in forming the ribosome?

    <p>rRNA (C)</p> Signup and view all the answers

    What happens when RNA polymerase encounters a terminator sequence during transcription?

    <p>RNA polymerase stops and detaches from DNA. (B)</p> Signup and view all the answers

    What role do transcription factors play in the transcription process?

    <p>They assist in RNA polymerase binding to the promoter. (A)</p> Signup and view all the answers

    What is the size range of messenger RNA (mRNA)?

    <p>100 - 10,000 nucleotides (A)</p> Signup and view all the answers

    What is the primary function of mRNA in the process of gene expression?

    <p>To carry genetic information from DNA to ribosomes for protein synthesis (B)</p> Signup and view all the answers

    Which of the following best describes alternative splicing?

    <p>The generation of different mRNAs and proteins from the same gene (D)</p> Signup and view all the answers

    What are exons?

    <p>Sequences that are preserved in the mRNA after splicing (C)</p> Signup and view all the answers

    How does capping and polyadenylation affect mRNA stability?

    <p>They help in the recognition and export of mRNA from the nucleus. (C)</p> Signup and view all the answers

    What is the role of RNA polymerase during transcription?

    <p>It synthesizes strands of mRNA from the DNA template. (C)</p> Signup and view all the answers

    In which direction is mRNA read during translation?

    <p>5’ to 3’ (D)</p> Signup and view all the answers

    What is a codon?

    <p>A three-nucleotide sequence that corresponds to a specific amino acid (C)</p> Signup and view all the answers

    What can result from the process of splicing?

    <p>The production of multiple proteins from a single gene (B)</p> Signup and view all the answers

    How many possible codons can be formed using a three-nucleotide sequence?

    <p>64 (B)</p> Signup and view all the answers

    What is the consequence of having introns in eukaryotic genes?

    <p>They can be removed through splicing to create functional mRNA. (A)</p> Signup and view all the answers

    Flashcards

    Transcription

    The process of creating RNA from a DNA template.

    Central Dogma of Molecular Biology

    The flow of genetic information from DNA to RNA to protein.

    Gene

    A segment of DNA that codes for a specific RNA molecule.

    RNA Polymerase

    The enzyme that synthesizes RNA during transcription.

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    Coding Strand (of DNA)

    The strand of DNA that has the same sequence as the transcribed RNA (except for thymine being replaced by uracil).

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    Central Dogma

    The process of genetic information flow from DNA to RNA to protein. It describes the fundamental principles of gene expression.

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    RNA vs DNA

    RNA utilizes ribose sugar and uracil base, while DNA uses deoxyribose sugar and thymine base. Both are nucleic acids, but they have distinct structural differences.

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    RNA Monomers

    The building blocks of RNA are called nucleotides, consisting of a sugar (ribose), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or uracil).

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    Phosphodiester Linkage

    The chemical bond that connects nucleotides in a RNA polymer. It forms between the phosphate group of one nucleotide and the sugar of the next.

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    RNA Structure

    Unlike DNA's double-helix structure, RNA is single-stranded. This allows for complex folding into 3D structures based on internal base-pairing interactions.

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    RNA Folding

    RNA molecules can fold into intricate 3D structures through interactions between bases within the same RNA molecule. These interactions can include both conventional and non-conventional base pairs.

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    RNA Function

    RNA plays a diverse range of roles in the cell, including information carrier (mRNA), adaptor molecule (tRNA), and catalytic enzyme (ribozyme).

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    Why RNA?

    RNA's single-stranded structure and ability to fold into complex 3D shapes allows for diverse roles in the cell, including information transfer, protein synthesis, and catalyst functions.

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    Aminoacyl-tRNA Synthetase

    An enzyme that attaches the correct amino acid to its corresponding tRNA molecule.

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    tRNA Specificity

    Each aminoacyl-tRNA synthetase is specific for only one type of amino acid and its corresponding tRNA(s).

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    Ribosome

    A complex molecular machine composed of ribosomal RNA (rRNA) and proteins that translates mRNA into a polypeptide chain.

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    Translation

    The process by which the genetic code in mRNA is decoded to synthesize a polypeptide chain.

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    RNA World Hypothesis

    The hypothesis that RNA was the main form of genetic material in early life, capable of both encoding genetic information and catalyzing chemical reactions.

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    Prokaryotic Transcription

    The process by which a gene's DNA sequence is copied into a messenger RNA (mRNA) molecule in prokaryotic cells.

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    Promoter

    A specific DNA sequence where RNA polymerase binds to begin transcription.

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    Sigma Factor

    A protein in prokaryotes that helps RNA polymerase recognize and bind to the promoter.

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    Terminator

    A specific DNA sequence signaling the end of transcription.

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    Template Strand

    The DNA strand that is used as a template for RNA synthesis.

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    Transcription Direction

    RNA synthesis proceeds in the 5' to 3' direction.

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    Types of RNA

    Different types of RNA molecules, each with a unique function: mRNA, tRNA, rRNA, and others.

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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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    Start Codon

    The first codon in a messenger RNA (mRNA) sequence that signals the start of protein synthesis.

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    Stop Codon

    A codon within a messenger RNA (mRNA) sequence that signals the termination of protein synthesis.

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    Reading Frame

    The specific sequence of codons in a messenger RNA (mRNA) molecule that determines the order of amino acids in a protein.

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    Open Reading Frame (ORF)

    The portion of a messenger RNA (mRNA) sequence that includes the start codon and ends with a stop codon, essentially coding for a protein.

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    5' UTR

    The 5' untranslated region of a messenger RNA (mRNA) molecule, located upstream of the start codon.

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    3' UTR

    The 3' untranslated region of a messenger RNA (mRNA) molecule, located downstream of the stop codon.

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    tRNA (Transfer RNA)

    A type of RNA molecule that carries a specific amino acid to the ribosome during protein synthesis, matching the codon sequence on mRNA.

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    Transcription factors

    Proteins that help RNA polymerase bind to DNA and start transcription.

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    Introns

    Non-coding sequences within a gene that are removed during splicing.

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    Exons

    Coding sequences within a gene that remain in the final mRNA after splicing.

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    Splicing

    The process of removing introns and joining exons together to create a mature mRNA molecule.

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    Alternative splicing

    A process where different combinations of exons can be included in the final mRNA, resulting in different proteins from the same gene.

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    Capping

    Adding a protective cap to the 5' end of mRNA, contributing to mRNA stability.

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    Polyadenylation

    Adding a tail of adenine nucleotides to the 3' end of mRNA, affecting its stability and translation efficiency.

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    Study Notes

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    Transcription - Synthesis of RNA

    • Transcription is the process of synthesizing RNA from a DNA template.

    The Central Dogma of Molecular Biology

    • The central dogma describes the flow of genetic information: DNA → RNA → protein.
    • DNA (deoxyribonucleic acid) contains the genetic code.
    • RNA (ribonucleic acid) acts as an intermediary, carrying the genetic code.
    • Proteins are synthesized according to the instructions encoded in mRNA.
    • DNA in the nucleus directs RNA synthesis.
    • RNA is transported to the cytosol to direct protein synthesis.

    Building Blocks of RNA

    • RNA monomers are called nucleotides.

    RNA vs. DNA: Monomers

    • RNA uses ribose as its sugar, while DNA uses deoxyribose.
    • RNA has uracil (U) where DNA has thymine (T).

    Nucleotides in RNA

    • Nucleotides in RNA are linked by phosphodiester linkages.
    • These linkages connect the 3' carbon of one nucleotide to the 5' carbon of the next.

    RNA Structure

    • RNA is typically single-stranded.
    • RNA can fold into complex three-dimensional structures.

    Advantages of RNA for Cells

    • RNA is synthesized from DNA, enabling cells to separate transcription and translation, improving regulation and control of gene expression.
    • This avoids exposing sensitive DNA to environments such as the cytosol before the information has a chance to be used.
    • RNA is more easily altered and destroyed then DNA and more susceptible to environmental conditions.

    Transcription

    • It is the process by which RNA is synthesized from a DNA template .
    • It results in a single-stranded RNA molecule (transcript).
    • It is carried out by RNA polymerases, which read the DNA template and synthesize a complementary RNA molecule.
    • RNA synthesis is only in the 5' → 3' direction.

    Eukaryotic Genes

    • Many contain introns.

    Function of Exons and Introns

    • Exons are the sequences that remain in mRNA.
    • Introns are removed after transcription.

    Alternative Splicing

    • Generating different mRNA from a single gene, which can then be translated into many different proteins.
    • The genome produces many more proteins than the number of genes present.

    mRNA Capping and Polyadenylation

    • mRNA modifications affect mRNA stability (how quickly it's degraded ) and translation efficiency (how efficiently it's translated).

    Export of mRNA

    • After transcription and modification, mRNA is exported from the nucleus to the cytosol for translation.

    Genetic Information Transmission (mRNA)

    • mRNA directs the synthesis of proteins.
    • The sequence is read in 5' to 3' direction for translation.

    Genetic Code

    • mRNA is translated into the amino-acid sequence of a protein.
    • A set of three nucleotides (codon) defines an amino acid.
    • There are 64 possible codons, but 20 amino-acids.

    Reading Frames

    • An RNA molecule has three potential reading frames.
    • Cells need a mechanism to determine the correct reading frame to synthesize the correct proteins.

    Start/Stop Codons

    • The start codon AUG defines the reading frame.
    • There are three stop codons (UAA, UAG, and UGA).

    Translation (mRNA Decoding)

    • mRNA is decoded on ribosomes.
    • This is known as 'translation'.
    • Ribosomes are complex molecular machines containing rRNA molecules and proteins.

    tRNA and Amino Acids

    • Transfer RNA (tRNA) molecules couple codons and amino acids.
    • tRNA has an anticodon sequence that matches mRNA codons.
    • Aminoacyl-tRNA synthetases attach the correct amino acid to its specific tRNA.
    • At least one aminoacyl-tRNA synthetase exists for each amino acid.

    Ribosomal RNA (rRNA)

    • rRNA molecules are essential components of ribosomes.

    RNA World Hypothesis

    • The idea that RNA may have been the primary genetic material in early life, holding both informational and catalytic activities (ribozymes).

    Regulation of Prokaryotic Transcription

    • RNA polymerase binds to the promoter (specific DNA regions) to initiate transcription.
    • A transcription factor (sigma factor in prokaryotes) helps to locate the promoter.
    • RNA is synthesized in the 5’→3’ direction using the template strand of DNA.
    • RNA polymerase stops at the termination sequences on the DNA, and is released from the DNA.

    Genes and DNA Strands

    • Genes can be encoded in both DNA strands.
    • The promoter's location and orientation help determine where RNA synthesis begins and which strand serves as the template.

    Multiple RNA Polymerases

    • Multiple RNA polymerases can simultaneously transcribe a gene.

    Different Types of RNA

    • Various RNA types (mRNA, tRNA, rRNA, and others) work together in protein synthesis.

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    BioMg1350 Fall 2024 Lecture Slides PDF

    Description

    Test your knowledge on the process of RNA transcription and the central dogma of molecular biology. This quiz covers key concepts about the synthesis of RNA from DNA, the building blocks of RNA, and comparisons between RNA and DNA. Perfect for students studying molecular biology.

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