Test practice (Unit 5 & 6)
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Questions and Answers

What occurs during the initiation phase of DNA replication?

  • The termination sequence is identified by the polymerase.
  • Polymerase begins to replicate DNA strands simultaneously.
  • Okazaki fragments are linked to form a contiguous strand.
  • The DNA strands are unwound at a specific sequence known as oriC. (correct)

    • Which statement best describes a successful mutant?

  • It is less successful than non-mutants.
  • It exhibits greater success than non-mutants. (correct)
  • It causes more errors in DNA replication.
  • It has no difference in success compared to non-mutants.

    • What is the role of primase in the elongation phase of DNA replication?

  • It adds RNA primers to template strands for replication. (correct)
  • It unwinds the DNA strands at the origin of replication.
  • It stops replication at the Tus-Ter sequence.
  • It forms Okazaki fragments that are later joined.

    • What is the primary outcome of bacterial conjugation?

    <p>New genetic information is transferred from one bacterium to another.</p> Signup and view all the answers

    Which process does NOT contribute to genetic diversity in bacteria?

    <p>Binary fission.</p> Signup and view all the answers

    At what point does DNA replication terminate?

    <p>At the Tus-Ter sequence recognized by polymerase.</p> Signup and view all the answers

    What is genetic engineering primarily aimed at achieving?

    <p>Alteration of an organism's genetics for desirable traits.</p> Signup and view all the answers

    During which process can bacteria acquire genetic material from their environment?

    <p>Bacterial transformation.</p> Signup and view all the answers

    What are the three components that make up a nucleotide?

    <p>Sugar, Phosphate, Nitrogenous base</p> Signup and view all the answers

    What is defined as a heritable change in the DNA sequence of an organism?

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

    Which of the following best describes a genotype?

    <p>The full collection of genes an organism can have</p> Signup and view all the answers

    What is the result of a missense mutation?

    <p>A different amino acid is incorporated into the protein</p> Signup and view all the answers

    What forms the structure of chromosomes in eukaryotic cells?

    <p>Linear DNA</p> Signup and view all the answers

    Which of the following correctly describes transcription?

    <p>The mapping of DNA to produce mRNA</p> Signup and view all the answers

    What is the role of codons in protein synthesis?

    <p>They represent sequences for amino acids</p> Signup and view all the answers

    Which type of mutation results in no change to the protein produced?

    <p>Silence mutation</p> Signup and view all the answers

    What is the primary function of Neuraminidase in the influenza virus?

    <p>To aid in the penetration of mucus in the respiratory tract</p> Signup and view all the answers

    What causes antigenic drift in the influenza virus?

    <p>Point mutations in genes coding for Hemagglutinin and Neuraminidase</p> Signup and view all the answers

    How does antigenic shift occur in the influenza virus?

    <p>When two different viruses infect the same cell and exchange genome segments</p> Signup and view all the answers

    What is the significance of the mutations in the genes coding for Hemagglutinin and Neuraminidase?

    <p>They cause new strains of the flu virus that may lead to epidemics</p> Signup and view all the answers

    What is the outcome when sufficient antigenic drift occurs?

    <p>A new flu vaccination is developed annually to target the strain</p> Signup and view all the answers

    What is the primary reason a virus cannot self-replicate?

    <p>It lacks the necessary cellular machinery for replication.</p> Signup and view all the answers

    Which part of a virus is responsible for recognizing and binding to host cell receptors?

    <p>Surface receptors</p> Signup and view all the answers

    What occurs during the uncoating phase of the viral replication cycle?

    <p>The viral capsid is removed, exposing the genome.</p> Signup and view all the answers

    What are the three mechanisms through which viruses can enter a host cell?

    <p>Fusion, receptor-mediated endocytosis, and direct penetration.</p> Signup and view all the answers

    What distinguishes RNA viruses from DNA viruses in terms of replication mistakes?

    <p>RNA viruses make more replication mistakes due to a lack of self-regulation.</p> Signup and view all the answers

    What is the purpose of the hemagglutinin spike protein on the influenza virus?

    <p>To facilitate the attachment to host cells.</p> Signup and view all the answers

    Which phase in the viral replication cycle involves the synthesis of the viral genome?

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

    What is a common outcome when a virus is released through apoptosis of the host cell?

    <p>Mature viral particles are released while the host cell dies.</p> Signup and view all the answers

    What is responsible for the rise of new strains of the flu virus?

    <p>Both B and C</p> Signup and view all the answers

    Antigenic drift can lead to pandemics.

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

    What glycoprotein on the surface of the influenza virus helps it attach to host cells?

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

    Neuraminidase helps in viral _____ of influenza by cutting sialic acid from host glycoproteins.

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

    Match the following terms with their definitions:

    <p>Antigenic Drift = Caused by point mutations in genes coding for viral proteins Antigenic Shift = Results from reassortment of viral genes from different viruses Neuraminidase = Enzyme that helps the virus penetrate mucus Hemagglutinin = Binds virus to sialic acid on host cell membranes</p> Signup and view all the answers

    Which of the following is NOT a common feature of viral structure?

    <p>Mitochondrial Membrane</p> Signup and view all the answers

    Viral replication involves the synthesis of both the viral genome and viral proteins.

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

    What is the process by which a virus enters a host cell via its envelope fusing with the host membrane?

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

    Viruses that have an RNA genome typically have a higher rate of ________ due to their lack of self-regulation.

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

    What mechanism allows the entire virus to be internalized into the host cell?

    <p>Receptor mediated endocytosis</p> Signup and view all the answers

    Match the following viral processes with their descriptions:

    <p>Attachment = Virus binds to host cell receptors Uncoating = Capsid is removed and genome is exposed Synthesis = Viral genome and proteins are produced Release = Virus exits host cell by various mechanisms</p> Signup and view all the answers

    Name one example of a virus mentioned in the content.

    <p>Influenza, HIV, or Ebola</p> Signup and view all the answers

    Influenza virus is characterized as a DNA virus.

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

    Study Notes

    Microbial Genetics

    • Heredity is based on DNA
    • DNA is made up of nucleotides, which comprise of a sugar (deoxyribose), phosphate, and a nitrogenous base
    • Four nitrogenous bases exist: Adenine, Thymine, Guanine, and Cytosine
    • Nucleic acids store and transfer information, holding the instructions for all proteins and metabolic reactions, defining an individual organism or cell
    • Nucleic acids are reproducible, passing information from DNA to RNA, leading to protein formation
    • Chromosomes, composed of DNA, are circular in prokaryotes and linear in eukaryotes
    • A gene, a sequence of nucleotides located at a specific locus on a chromosome, can have different versions, called alleles
    • Genotype represents the complete set of genes an organism possesses
    • Phenotype encompasses the physical characteristics of an individual, influenced by both the genes and the environment

    Protein Synthesis

    • Transcription, the process of reading a specific section of the genome to create proteins, involves the conversion of DNA to messenger RNA (mRNA)
    • Translation interprets mRNA to synthesize a specific protein (mRNA to Protein)
    • The codon table, a tool used to decipher the relationship between mRNA codons and amino acids, reveals that every three bases code for a specific amino acid

    Mutations

    • Mutations are heritable changes in an organism's DNA sequence
    • Mutants may exhibit phenotypic differences compared to the "wild type", the most prevalent form in nature
    • Mutations can affect protein function:
      • Silent mutation: no effect on protein function
      • Missense mutation: a different amino acid is incorporated into the protein
      • Nonsense mutation: converts a codon into a stop codon, often leading to a non-functional protein

    Adaptation and Mutations

    • Mutants can be:
      • Successful: advantageous (mutant surpasses non-mutants)
      • Neutral: no difference in success compared to non-mutants
      • Deleterious: less successful than non-mutants
    • Adaptation occurs when a beneficial mutation arises within a population and eventually becomes the dominant form due to increased success of mutant individuals

    DNA/Chromosome Replication

    • Consists of three stages: Initiation, Elongation, and Termination

    Initiation

    • Replication starts at the origin of replication (oriC)
    • oriC is a specific sequence of bases on DNA that marks the beginning of DNA replication
    • DNA strand unwinds at oriC, generating two strands
    • Helicase unwinds the DNA, creating two replication forks

    Elongation

    • Polymerase replicates the two strands, but can only extend existing strands
    • Primase primes the strands for replication by adding a primer recognized by the polymerase
    • Replication initiates simultaneously in both directions: leading and lagging strands
    • Okazaki fragments, short DNA segments created during lagging strand replication, are joined by ligase to create a contiguous strand
    • Topoisomerases (gyrase) manage DNA winding problems

    Termination

    • Replication halts when the polymerase encounters the termination (Tus-Ter) sequence
    • Two new loops form and migrate to the bacterial ends
    • A septum forms to create two new cells

    Gene Transfer

    • Binary fission is simple asexual cell division, lacking genetic diversity
    • Bacterial conjugation involves a donor cell transferring genetic information to a recipient cell, promoting genetic diversity
    • Bacterial transformation involves cells acquiring genetic information from the environment, leading to the acquisition of new traits and genetic diversity
    • Bacterial transduction occurs when a bacterial cell is infected by a bacteriophage
    • Viral DNA integrates into the bacterial DNA, replicating and carrying portions of bacterial and viral DNA
    • The infected phage then infects other bacteria, transferring the combined DNA

    Biotechnology

    • Biotechnology is the science of using living systems to improve humankind
    • Genetic engineering involves altering an organism's genetics to produce desirable traits

    What is a Virus?

    • A virus is an acellular infectious agent that cannot self-replicate.
    • Viruses must infect a cell to reproduce.
    • Examples of viruses include Influenza, HIV, and Ebola.

    Viral Structure

    • Viral structure varies but has common elements.
    • All viruses have a genome made of either RNA or DNA.
    • Viruses have a protein coat called a Capsid.
    • Some viruses also have an envelope composed of a lipid bi-layer.
    • Viruses have surface receptors, often spikes of protein or glycoprotein.

    Viral Replication Cycle

    • Viral replication depends on the type of genome a virus possesses.
    • Different types of viruses have distinct replication strategies.

    Viral Attachment

    • Proteins on the viral envelope or Capsid bind to specific receptors on host cells.

    Viral Penetration

    • There are three main ways a virus enters a host cell:
      • Direct penetration (naked viruses): Only the viral genome enters the host cell.
      • Fusion: The viral envelope fuses with the host membrane, allowing the capsid containing the genome to enter.
      • Receptor-mediated endocytosis: Attachment stimulates endocytosis of the entire virus.

    Viral Uncoating

    • The virus removes its Capsid (uncoats), exposing the nucleic acid genome to the cytoplasm.

    Viral Transport to Nucleus

    • The viral genome enters the host cell nucleus.

    Viral Synthesis

    • The viral genome is reproduced through transcription in the nucleus.
    • Viral proteins are produced through translation in the cytoplasm.

    Viral Assembly

    • Newly produced viral components (genome and Capsid) assemble into new viruses.

    Viral Release

    • Viruses are released from the host cell through one of three mechanisms:
      • Apoptosis: The host cell lyses, releasing mature viral particles. The host cell dies.
      • Budding: The virus buds through the nuclear or plasma membrane, acquiring an envelope. The host cell survives.
      • Exocytosis: Viruses leave the host cell using vesicles; the host cell survives.

    Influenza Virus

    • Influenza virus is an enveloped RNA virus.
    • RNA viruses mutate more frequently than DNA viruses.
    • RNA viruses can adapt to environmental changes more readily due to their high mutation rates.
    • Influenza has two surface proteins: Hemagglutinin (H) and Neuraminidase (N).

    Hemagglutinin (H)

    • This glycoprotein binds the virus to cells with sialic acid on their membranes.
    • Sialic acid is a receptor found on most vertebrate cells.
    • Hemagglutinin helps the virus enter the cell.

    Neuraminidase (N)

    • This enzyme aids in penetration of the respiratory tract mucus and viral shedding.
    • Neuraminidase cleaves sialic acid from host glycoproteins during viral release (budding).

    Antigenic Variation

    • There are two main types of antigenic variation in Influenza viruses:
      • Antigenic drift: This occurs due to point mutations in the genes coding for Hemagglutinin and Neuraminidase.
      • Antigenic shift: This occurs due to reassortment of viral genes from two different viruses infecting the same cell.

    Antigenic Drift

    • Mutations in Hemagglutinin and Neuraminidase genes alter the antigens.
    • This makes it harder for the host's immune system to recognize and fight the virus.
    • Antigenic drift causes new flu epidemics (localized flu) and necessitates annual flu vaccine updates.

    Antigenic Shift

    • Two different viruses exchange large portions of their genomes.
    • The resulting virus is antigenically distinct from both parent viruses.
    • Antibodies against the parent viruses are ineffective against the new virus.
    • This can lead to pandemics.
      • Examples:
        • H5N1 (bird flu)
        • H1N1 (swine flu)

    Swine Flu Viroid Re-assortment

    • This is an example of antigenic shift where the genes of a swine flu virus re-assort, leading to a new, potentially pandemic strain.

    What is a Virus?

    • A virus is an acellular infectious agent that cannot self-replicate.
    • Viruses must infect a cell to make copies of themselves.
    • Examples of viruses include Influenza, HIV, and Ebola.

    Viral Structure

    • Viruses have varied structures, but there are common features.
    • Viral structures include RNA or DNA genomes, protein capsids, envelope lipid bi-layers, and surface receptors (spikes) made of protein or glycoprotein.

    Viral Replication Cycle

    • The replication cycle of a Virus depends on its genome.

    Viral Replication Cycle (Steps)

    • Attachment: Proteins on the viral envelope or capsid recognize and bind with target host cell receptors.

    • Penetration: Entry can occur in three ways:

      • Direct penetration (naked viruses): Only the viral genome enters the host (typical of bacteriophages);
      • Fusion: Viral envelope fuses with the host membrane, the capsid containing the genome enters the cell (e.g. HIV);
      • Receptor-mediated endocytosis: Attachment stimulates endocytosis of the whole virus (e.g. Influenza).

    • Uncoating: The virus removes the capsid and the nucleic acid of the genome is exposed to the cytoplasm.

    • Transport to Nucleus: Viral genome enters the nucleus.

    • Synthesis (Transcription & Translation): Reproduction of the viral genome (transcription in the nucleus) and viral proteins (translation in the cytoplasm).

    • Assembly: Assembly of new virions (complete virus). The genome and capsid are put together to form a new virus.

    • Release: Release of the virus from the host cell (viral shedding). Release occurs by one of three mechanisms:

      • Apoptosis: The host cell lyses and releases mature viral particles (naked viruses); The host cell dies.
      • Budding: Through the nuclear or plasma membrane, creating an envelope; Does not kill the host.
      • Exocytosis: Viruses leave the host cell using vesicles; Does not kill the host.

    Influenza Virus

    • Influenza virus is an enveloped RNA virus.
    • RNA viruses have higher mutation rates than DNA viruses as they don't have self-regulation and DNA correction mechanisms.
    • This makes RNA viruses highly adaptable to environmental changes.
    • The envelope of the influenza virus is covered with two proteins (antigens) essential for the infection process:
      • Hemagglutinin (H) spike
      • Neuraminidase (N) spike

    Hemagglutinin (H) spike

    • Glycoprotein on the surface of the Influenza virus binds the virus to cells with sialic acid on host cell membranes, such as cells in the upper respiratory tract or erythrocytes.
    • This helps the virus enter the cell.
    • Sialic Acid is a receptor found on most vertebrate cells.

    Neuraminidase (N) spike

    • Enzyme that helps the virus penetrate the mucus of the respiratory tract & aids in viral shedding of influenza (budding).
    • It does this by cutting sialic acid from host glycoproteins as the virus is being released.

    Antigenic Variation

    • Mutations in genes that code for these two proteins (H and N) are responsible for the development of new strains of Flu.
    • Antigenic variation occurs in two ways with the Flu Virus:
      • Antigenic drift results from point mutation of genes coding for Hemagglutinin & Neuraminidase.
      • Antigenic shift is caused by re-assortment of viral genes.

    Antigenic Drift

    • Mutations in genes that code for Hemagglutinin & Neuraminidase.
    • These two proteins are the antigens that cause the formation of host antibodies.
    • It produces new strains of flu virus that host antibodies won't recognize.
    • If enough of an antigenic drift occurs, it will cause a new flu epidemic (localized flu).
    • Antigenic drift causes new formulations of flu vaccine every year.

    Antigenic Shift

    • Results from gene re-assortment from two different viruses that infect the same cell.
    • Viruses exchange a large part of their genome.
    • The virus that emerges is antigenically different from either of the two viruses.
    • Antibodies formed from the two viruses are ineffective against the new combined virus genome.
    • For example:
      • H5N1 = bird flu
      • H1N1 = swine flu
    • Can lead to Pandemics.

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    Description

    This quiz covers key concepts in microbial genetics, including heredity, DNA structure, the role of nucleic acids, chromosomes, genes, and the processes of protein synthesis. Understand how genetic information is stored, transferred, and expressed in organisms. Test your knowledge on the basics of genetics and protein formation.

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