Biology: DNA and RNA Basics
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Questions and Answers

What is the primary function of tRNA?

  • Forms ribosomes
  • Stores genetic information
  • Catalyzes peptide bond formation
  • Transfers amino acids to ribosomes (correct)

    • DNA replication follows a conservative model.

    False

    What experiment tested the hypothesis of semiconservative replication?

    Meselson and Stahl Experiment

    During DNA replication, _____ breaks hydrogen bonds between complementary bases, unzipping the DNA double helix.

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

    Match the steps of DNA replication with their functions:

    <p>Helicase = Unzips the DNA double helix Primase = Adds RNA primers to the DNA strand DNA Polymerase = Synthesizes new DNA strands SSBs = Stabilizes separated DNA strands</p> Signup and view all the answers

    What percentage of DNA will have light density after two generations in the Meselson and Stahl experiment?

    <p>50% light density</p> Signup and view all the answers

    Cytokinesis is the process of nuclear division.

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

    What is the role of capping in post-transcriptional modifications?

    <p>It aids in ribosome binding and stabilizes mRNA.</p> Signup and view all the answers

    Polyadenylation removes introns from the mRNA.

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

    What process follows transcription to produce functional mRNA?

    <p>Post-transcriptional modifications</p> Signup and view all the answers

    In the lac operon model, the presence of _____ inactivates the repressor and allows transcription.

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

    Match the components of the lac operon with their functions:

    <p>Structural Genes = Code for enzymes to metabolize lactose Regulator Gene = Produces repressor molecule Promoter = Initiates transcription by binding RNA polymerase Operator = Region where the repressor binds to block transcription</p> Signup and view all the answers

    What is the primary role of DNA ligase during DNA replication?

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

    DNA replication occurs only in the S phase of cell division in eukaryotic cells.

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

    What model describes the mechanism of DNA replication according to Meselson and Stahl?

    <p>Semiconservative model</p> Signup and view all the answers

    The __________ stabilizes single-stranded DNA during replication.

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

    Match each DNA replication component with its function:

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

    How is the leading strand synthesized during DNA replication?

    <p>Consecutively towards the replication fork</p> Signup and view all the answers

    Okazaki fragments are formed on the leading strand during replication.

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

    What provides the energy for DNA synthesis?

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

    In DNA replication, the __________ serves as the template strand.

    <p>original DNA strand</p> Signup and view all the answers

    Which amino acid is coded by the mRNA codon 5'-AAG-3'?

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

    The genetic code is the same for all organisms including viruses.

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

    What are introns?

    <p>Non-coding sequences removed before translation.</p> Signup and view all the answers

    Transcription occurs in the ______ of a cell.

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

    Which of the following describe the features of the genetic code?

    <p>Universal and degenerate</p> Signup and view all the answers

    The start codon is AUG and it codes for Lysine.

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

    Define a cistron in the context of genetics.

    <p>A section of DNA that codes for a specific polypeptide.</p> Signup and view all the answers

    MRNA is synthesized in the ______ to ______ direction.

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

    Match the following terms with their descriptions:

    <p>Exons = Coding sequences for amino acids Introns = Non-coding sequences removed from mRNA Codons = Triplets of nucleotides on mRNA Helicase = Enzyme that unwinds DNA strands</p> Signup and view all the answers

    During elongation, RNA polymerase reads the DNA template strand in the 5' to 3' direction.

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

    What is the function of RNA polymerase during transcription?

    <p>Catalyzes the synthesis of mRNA</p> Signup and view all the answers

    The mRNA strand is synthesized in the 3' to 5' direction.

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

    What sequence of nucleotide corresponds to the DNA template strand 3'-ATCGTACT-5' in mRNA?

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

    During transcription, helicase __________ the DNA double helix.

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

    Match the following key molecules to their functions:

    <p>Helicase = Unwinds the DNA double helix RNA Polymerase = Synthesizes mRNA molecules Promoter Region = Binds RNA polymerase to initiate transcription Terminator = Signals the end of transcription</p> Signup and view all the answers

    At what point does transcription terminate?

    <p>When RNA polymerase reaches a termination sequence</p> Signup and view all the answers

    The mRNA strand is identical to the coding strand of DNA, except that uracil replaces thymine.

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

    Where does mRNA go after transcription is complete?

    <p>The cytoplasm</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

    Which of the following is NOT a key feature of mRNA?

    <p>It is always synthesized in the 3' to 5' direction</p> Signup and view all the answers

    Study Notes

    DNA and RNA

    • DNA is deoxyribonucleic acid, a double-stranded molecule.
    • RNA is ribonucleic acid, a single-stranded molecule.
    • DNA stores genetic information.
    • RNA carries instructions for protein synthesis.
    • Nucleotides are the building blocks of both DNA and RNA.
    • Each nucleotide comprises a pentose sugar, a phosphate group, and a nitrogenous base.
    • DNA sugars are deoxyribose, and RNA sugars are ribose.
    • DNA bases are adenine (A), thymine (T), guanine (G), and cytosine (C).
    • RNA bases are adenine (A), uracil (U), guanine (G), and cytosine (C).
    • In DNA, A pairs with T via 2 hydrogen bonds, and G pairs with C via 3 hydrogen bonds.
    • In RNA, A pairs with U via 2 hydrogen bonds, and G pairs with C via 3 hydrogen bonds.

    Nucleotide Structure

    • DNA and RNA are made of nucleotides.
    • Each nucleotide is a monomer.
    • Nucleotides are formed by linking a pentose sugar (deoxyribose/ribose), a phosphate group, and a nitrogenous base together.
    • Phosphate group gives DNA and RNA a negative charge.

    DNA Structure

    • DNA is a double helix.
    • Two strands are antiparallel, meaning they run in opposite directions (5' to 3' and 3' to 5').
    • Strands are held together by hydrogen bonds between complementary bases.
    • A pairs with T, and G pairs with C.
    • The sugar-phosphate backbone forms the outside of the double helix.
    • Bases are stacked in the interior of the double helix.
    • Major and minor grooves in the helix provide sites for protein interactions.

    RNA Structure

    • RNA is single-stranded.
    • RNA is less stable than DNA.
    • RNA sugar is ribose.
    • RNA contains uracil (U) instead of thymine (T).
    • Several types of RNA exist (mRNA, tRNA, rRNA).

    DNA Replication

    • DNA replication is semi-conservative.
    • Each new DNA molecule consists of one original (parental) strand and one new strand.
    • Enzymes like helicase unwind the DNA double helix, and enzymes like polymerase synthesize new strands using the original strands as templates.
    • Okazaki fragments are short DNA fragments synthesized on the lagging strand, which is replicated in short bursts.
    • Ligase seals the gaps between Okazaki fragments.

    Protein Structure

    • Proteins are made of amino acids.
    • Primary structure: Linear sequence of amino acids.
    • Secondary structure: Folding of the polypeptide chain (α-helices and β-sheets).
    • Tertiary structure: 3D folding of the polypeptide chain.
    • Quaternary structure: Association of multiple polypeptide chains.

    Transcription

    • Transcription is the synthesis of RNA from a DNA template.
    • RNA polymerase binds to a promoter region on the DNA.
    • RNA polymerase unwinds the DNA double helix and uses one strand as a template to synthesize a complementary RNA molecule.
    • The RNA molecule detaches at the termination sequence.
    • mRNA carries the genetic message from the DNA to the ribosomes
    • DNA provides the template.
    • RNA polymerase is the enzyme.
    • mRNA is produced.

    Regulation of Gene Expression

    • Gene expression is the process by which genetic information is used to create functional gene products.
    • Regulation of gene expression is crucial for maintaining cellular homeostasis.
    • Gene regulation can occur at various stages.
    • Prokaryotes use operons to simultaneously regulate multiple genes.
    • Eukaryotes employ various mechanisms like transcription factors, histone modification and DNA methylation.

    Mutations

    • Mutations are changes in DNA sequences.
    • Mutations can be spontaneous (random) or induced by environmental factors.
    • Mutations can be small-scale (gene mutations—e.g., substitution, insertion, deletion) or large-scale (chromosome mutations—e.g., duplication, deletion, inversion).
    • Mutations can have diverse effects, from no effect to a drastic change in the protein product, and/or cellular function.

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    Description

    This quiz covers the fundamental differences and structures of DNA and RNA, including nucleotide composition and pairings. Test your knowledge on the essential roles these molecules play in genetics. Learn about deoxyribonucleic acid and ribonucleic acid in detail.

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