Biology Chapter: DNA and RNA Functions
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What is the primary role of RNA in cells?

  • Carrying instructions for protein synthesis (correct)
  • Encoding genetic blueprints
  • Storing genetic information
  • Forming the backbone of DNA

    • DNA is a single-stranded molecule.

    False

    What type of sugar is found in RNA?

    Ribose

    In DNA, adenine (A) pairs with ______.

    <p>thymine (T)</p> Signup and view all the answers

    Match the following types of RNA with their primary functions:

    <p>mRNA = Carries genetic code from DNA to ribosomes tRNA = Brings specific amino acids during protein synthesis rRNA = Forms ribosome structure and catalyzes peptide bond formation snRNA = Involved in splicing of pre-mRNA</p> Signup and view all the answers

    What is the primary function of DNA ligase during replication?

    <p>Seals gaps between Okazaki fragments</p> Signup and view all the answers

    DNA replication is a completely conservative process.

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

    What are the two main types of nucleotides paired in DNA?

    <p>Adenine with Thymine, Guanine with Cytosine</p> Signup and view all the answers

    During DNA replication, the enzyme __________ unwinds the DNA double helix.

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

    Match the component of DNA replication with its function:

    <p>Helicase = Unwinds DNA Primase = Synthesis of RNA primers DNA Polymerase = Adds nucleotides Single-Strand Binding Proteins = Stabilizes single strands</p> Signup and view all the answers

    What is the role of RNA during protein synthesis?

    <p>Transports amino acids to ribosomes</p> Signup and view all the answers

    What defines the semiconservative nature of DNA replication?

    <p>Each new DNA molecule consists of one parental strand and one newly synthesized strand.</p> Signup and view all the answers

    In conservative replication, you would observe intermediate densities of DNA in the first generation.

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

    What role does helicase play during DNA replication?

    <p>Helicase unzips the DNA by breaking hydrogen bonds.</p> Signup and view all the answers

    The _______ protein stabilizes single-stranded DNA during replication.

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

    Match the DNA replication functions with their respective proteins:

    <p>Helicase = Unzips DNA by breaking hydrogen bonds. DNA Primase = Adds RNA primers to initiate replication. DNA Ligase = Joins Okazaki fragments. DNA Polymerase = Synthesizes DNA strands by adding nucleotides.</p> Signup and view all the answers

    Which of the following correctly describes the leading and lagging strands in DNA replication?

    <p>The leading strand is synthesized continuously; the lagging strand is synthesized discontinuously.</p> Signup and view all the answers

    Denaturation of proteins involves breaking peptide bonds between amino acids.

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

    What is the primary structure of a protein?

    <p>The sequence of amino acids in a polypeptide chain.</p> Signup and view all the answers

    What is the role of the A site in the ribosome during translation?

    <p>It is the entry site for tRNA carrying an amino acid.</p> Signup and view all the answers

    Translation is the process of converting DNA information directly into proteins.

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

    What amino acid does the start codon AUG code for?

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

    In the Lac Operon model, when lactose is present, it binds to the ______ and inactivates it.

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

    Match the following gene regulation mechanisms with their descriptions:

    <p>Transcription Factors = Proteins that control the rate of transcription Histone Acetylation = Loosens chromatin structure for gene expression DNA Methylation = Inactivates genes by adding methyl groups Negative Feedback = Regulates metabolism by inhibiting product synthesis</p> Signup and view all the answers

    Which class of protein is primarily responsible for structural functions?

    <p>Fibrous proteins</p> Signup and view all the answers

    The mRNA codon AUG codes for Lysine.

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

    How many different short proteins can be built with only 5 amino acids?

    <p>3,200,000</p> Signup and view all the answers

    The first step of protein synthesis involves the conversion of DNA to ______.

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

    Match the following DNA terms with their definitions:

    <p>Sense Strand = The strand that matches the sequence of the mRNA. Antisense Strand = The strand serving as a template for mRNA synthesis. Codon = A sequence of three nucleotides coding for an amino acid. Exons = Coding sequences that are expressed in proteins.</p> Signup and view all the answers

    What is a significant characteristic of the genetic code?

    <p>It is universal and triplet-based.</p> Signup and view all the answers

    Denaturation of a protein enhances its function.

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

    What are the two major steps involved in protein synthesis?

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

    The process of _____ synthesizing RNA from a DNA template is known as transcription.

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

    Which of the following codons signals the end of translation?

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

    What is the primary role of RNA polymerase during transcription?

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

    The mRNA sequence is identical to the template strand of DNA.

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

    What are the start and stop codons in the genetic code?

    <p>Start codon: AUG; Stop codons: UAA, UAG, UGA</p> Signup and view all the answers

    The process of copying DNA into mRNA is called __________.

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

    Match the following components involved in translation with their roles:

    <p>mRNA = Carries genetic instructions from DNA to ribosomes tRNA = Delivers specific amino acids to the ribosome Ribosome = Site of protein synthesis Release Factor = Triggers the release of the polypeptide chain at termination</p> Signup and view all the answers

    During which step of translation does peptide bond formation occur?

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

    The amino acids are added to the polypeptide chain during the termination phase of translation.

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

    What happens to the newly formed mRNA at the end of transcription?

    <p>mRNA detaches from the DNA and exits the nucleus via nuclear pores.</p> Signup and view all the answers

    The two main functional sites of tRNA are the __________ and __________.

    <p>anticodon; amino acid attachment site</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the genetic code?

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

    Study Notes

    DNA and RNA

    • DNA (Deoxyribonucleic Acid) is the primary molecule for storing and transmitting genetic information, located in the nucleus (eukaryotes) or nucleoid region (prokaryotes).
    • DNA has a double-stranded double helix structure.
    • RNA (Ribonucleic Acid) plays a major role in protein synthesis and gene regulation, found in both nucleus and cytoplasm.
    • RNA has a single-stranded structure.
    • DNA stores genetic blueprints; RNA acts as an intermediary for protein synthesis instructions.

    Nucleotide Structure

    • Nucleotides are the basic units of DNA and RNA.
    • Each nucleotide comprises:
      • A pentose sugar (deoxyribose in DNA, ribose in RNA).
      • A phosphate group (gives DNA and RNA a negative charge).
      • A nitrogenous base (purines: adenine (A), guanine (G); pyrimidines: cytosine (C), thymine (T in DNA), uracil (U in RNA)).

    DNA Structure

    • Watson and Crick discovered the double helix structure of DNA in 1953, based on Franklin's X-ray diffraction data.
    • DNA strands run antiparallel (5' → 3' and 3' → 5').
    • The backbone consists of alternating sugar (deoxyribose) and phosphate groups.
    • Base pairs: A pairs with T (2 hydrogen bonds); G pairs with C (3 hydrogen bonds).
    • Hydrogen bonds stabilize the double helix.
    • Major and minor grooves are structural features for protein interactions.

    RNA Structure

    • RNA is single-stranded and less stable than DNA.
    • RNA has ribose sugar with a hydroxyl group at the 2' position.
    • RNA uses uracil (U) instead of thymine (T) as a base.
    • Types of RNA include:
      • mRNA (messenger RNA): Carries genetic code from DNA to ribosomes for protein synthesis.
      • tRNA (transfer RNA): Carries amino acids to ribosomes during protein synthesis; has a cloverleaf shape.
      • rRNA (ribosomal RNA): Forms the ribosome structure, catalyzes peptide bond formation.

    DNA Replication

    • DNA replication is the process of copying DNA to ensure genetic continuity.
    • The process is semi-conservative; each new DNA molecule has one original and one new strand.
    • Steps include initiation (helicase unwinds DNA; topoisomerase prevents overwinding), priming (primase adds RNA primers), elongation (DNA polymerase adds nucleotides; leading strand is continuous, lagging strand is discontinuous with Okazaki fragments), and termination (replication ends).
    • DNA ligase seals gaps between Okazaki fragments.

    Base Pairing Rules

    • DNA base pairing: A with T; G with C.
    • RNA base pairing: A with U; G with C.

    Protein Synthesis

    • Protein synthesis involves two main steps: transcription and translation.
    • Transcription: DNA is transcribed to mRNA in the nucleus using RNA polymerase.
    • Translation: mRNA is translated to a polypeptide chain (protein) at ribosomes in the cytoplasm.

    Transcription

    • RNA polymerase synthesizes a complementary mRNA strand from a DNA template strand (antisense strand).
    • mRNA carries the genetic code to the ribosomes.

    Translation

    • Ribosomes read mRNA codons.
    • tRNA molecules bring specific amino acids to the ribosome.
    • Amino acids are linked together to form a polypeptide chain.
    • Steps include initiation, elongation, and termination.
    • Post-translational modifications occur after synthesis.

    Regulation of Gene Expression

    • Gene expression is regulated to control cell metabolism and protein synthesis.
    • Operons (prokaryotes) control groups of genes responsible for a specific function; examples include the lac operon (activation by substrate) and tryptophan operon (repression by product).
    • Eukaryotes use multiple mechanisms, including transcription factors, histone acetylation, and DNA methylation, to control gene expression.
    • Epigenetics involves changes in gene activity without altering the DNA sequence.

    Mutations

    • Mutations are changes in DNA sequences.
    • Types include gene mutations (substitutions, insertions, deletions) and chromosome mutations (duplications, deletions, inversions, translocations).
    • Mutations can be spontaneous or induced by external factors (mutagens).
    • Effects can be neutral, beneficial (e.g., sickle-cell anemia), or harmful.

    Genetic Engineering

    • Genetic engineering modifies an organism's genome to obtain desired traits or produce specific products.
    • Steps include isolating the target gene, inserting it into a vector, transforming host cells, selecting and cloning successful transformations, and expressing the target gene.
    • Tools include restriction enzymes and DNA ligase.
    • Applications include medicine (insulin, gene therapy), agriculture (GM crops), and industry (enzymes, biofuels).
    • Risks and ethical considerations exist surrounding genetic engineering.

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    Description

    Test your knowledge on the roles of RNA and DNA in cells, as well as the processes related to DNA replication. This quiz covers key concepts and functions associated with nucleic acids and their importance in biology. Perfect for reviewing essential topics in molecular biology!

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