Chromatin Structure and Function Exam 1
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Questions and Answers

What is the role of telomeres in chromosomes?

  • To initiate DNA replication
  • To mark histones for remodeling
  • To prevent degradation and ensure complete replication (correct)
  • To enable proper chromosome segregation

    • The leading strand during DNA replication is synthesized discontinuously as Okazaki fragments.

    False

    What enzyme is responsible for sealing nicks in the DNA backbone during replication?

    Ligase

    Euchromatin is the form of chromatin that is ______ and is transcriptionally active.

    <p>less condensed</p> Signup and view all the answers

    Which of the following processes occurs during PCR?

    <p>Separating DNA strands by heat</p> Signup and view all the answers

    Match the parts of chromosomes with their functions:

    <p>Telomeres = Prevent degradation and ensure complete replication Centromeres = Enable proper chromosome segregation Origins of Replication = Where DNA replication begins Chromatin = Complex of DNA and proteins</p> Signup and view all the answers

    Heterochromatin is the form of chromatin that is transcriptionally active.

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

    What is the resting potential of a neuron?

    <p>-70 mV</p> Signup and view all the answers

    Inhibitory neurons increase the likelihood of firing action potentials.

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

    What triggers synaptic vesicles to dock at the membrane?

    <p>Calcium ions (Ca²⁺)</p> Signup and view all the answers

    ATP production in mitochondria is powered by the flow of H⁺ ions through __________.

    <p>ATP synthase</p> Signup and view all the answers

    Match the following components of cellular respiration and photosynthesis:

    <p>Electron Transport Chain = Creates a H⁺ gradient ATP Synthase = Uses H⁺ gradient to synthesize ATP Light Reactions = Pumps H⁺ into thylakoid lumen Calvin Cycle = Produces sugar</p> Signup and view all the answers

    What role do +TIPs play in microtubule dynamics?

    <p>They stabilize the growing end of microtubules.</p> Signup and view all the answers

    Gamma-tubulin is essential for initiating microtubule growth.

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

    What are the three main types of microtubules present in the mitotic spindle?

    <p>Astral, Kinetochore, Interpolar</p> Signup and view all the answers

    In anaphase, __________ microtubules shorten to pull sister chromatids apart.

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

    Match the motor proteins with their direction of movement:

    <p>Dynein = Moves toward the '+' end Kinesin = Moves toward the '-' end</p> Signup and view all the answers

    What happens to microtubules when GTP-tubulin cap is lost?

    <p>Microtubules depolymerize rapidly.</p> Signup and view all the answers

    Kinesin proteins typically transport cargoes inward toward the cell center.

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

    Where is the actin cytoskeleton primarily located within the cell?

    <p>Near the cell cortex, just beneath the plasma membrane</p> Signup and view all the answers

    What is the primary function of SNAREs in cellular processes?

    <p>Vesicle fusion</p> Signup and view all the answers

    The __________ microtubules overlap at the center of the cell and help maintain spindle structure.

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

    Rabs are responsible for regulating vesicle fusion with target membranes.

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

    Match the phases with their events during mitosis:

    <p>Metaphase = Chromosomes align at the metaphase plate Anaphase = Sister chromatids are pulled apart</p> Signup and view all the answers

    What are the proteins that mediate endocytosis?

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

    Proteins that lack specific sorting signals are typically transported by default to the __________.

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

    Which intermediate filaments provide structural support and flexibility in epithelial cells?

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

    The process known as ER-associated degradation (ERAD) involves tagging misfolded proteins with ubiquitin.

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

    Match the following components with their respective roles:

    <p>Clathrin = Mediates endocytosis COPI = Trafficking from Golgi to ER COPII = Trafficking from ER to Golgi Lamin = Forms the nuclear lamina</p> Signup and view all the answers

    Name one type of protein involved in vesicle formation during transport.

    <p>Clathrin, COPI, or COPII</p> Signup and view all the answers

    What is the first step in the assembly of intermediate filaments?

    <p>Two monomers wrap around each other to form a coiled-coil dimer</p> Signup and view all the answers

    Intermediate filaments have distinct polarity.

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

    What happens to proteins without signals for vesicular trafficking?

    <p>They remain in the cytoplasm</p> Signup and view all the answers

    What is the function of intermediate filaments in the nucleus?

    <p>They support the nucleus, maintain its shape, and regulate DNA replication and transcription.</p> Signup and view all the answers

    Intermediate filaments do not require ______ for their assembly.

    <p>ATP or GTP</p> Signup and view all the answers

    Match the following components with their description:

    <p>Alpha-tubulin = A component of the microtubule that is slow-growing Beta-tubulin = A component of the microtubule that is fast-growing Centrosome = Microtubule-organizing center Dynamic instability = Cycle of growth and shrinkage at the '+' end of microtubule</p> Signup and view all the answers

    What happens during phosphorylation of intermediate filaments?

    <p>They lead to disassembly</p> Signup and view all the answers

    Microtubules are composed of heterodimers of alpha- and beta-tubulin.

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

    What triggers the breakdown of the nuclear envelope during mitosis?

    <p>Phosphorylation of nuclear lamins</p> Signup and view all the answers

    During dynamic instability, _______ hydrolyzes to GDP, causing shrinkage.

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

    What drives the fast-growing end of microtubules?

    <p>Beta-tubulin exposure</p> Signup and view all the answers

    Signup and view all the answers

    Study Notes

    Exam 1

    • Chromatin: A complex of DNA and proteins, primarily histones, that compacts DNA in the nucleus.
    • Nucleosome: The fundamental unit of chromatin, which is 147 base pairs of DNA wrapped around a core of 8 histone proteins (an octamer of H2A, H2B, H3, and H4).
    • H1 histone: Links nucleosomes, forming higher-order structures.
    • Chromatin Organization Levels: Nucleosome → 10 nm fiber → 30 nm fiber → higher-order folding into chromosomes.

    Types of Chromatin

    • Euchromatin: Loosely packed, transcriptionally active regions.
    • Heterochromatin: Densely packed, transcriptionally inactive regions.
      • Constitutive Heterochromatin: Always inactive, found in centromeres and telomeres.
      • Facultative Heterochromatin: Can switch between active and inactive states, for example, X-chromosome inactivation.

    Gene and Sequence Complexity in Eukaryotic Genomes

    • Unique Sequences: Single-copy genes coding for proteins.
    • Repetitive Sequences:
      • Moderately Repetitive: Includes rDNA, tRNA, and histone genes.
      • Highly Repetitive: Found in centromeres and telomeres (e.g., satellite DNA).
    • Complexity arises from both coding and non-coding regions.

    Nature of the Nucleolus

    • Definition: A subnuclear structure where rRNA is synthesized and ribosome assembly begins.
    • Location: Found in tandem arrays on acrocentric chromosomes.
    • Function: Involved in rRNA transcription, catalyzed by RNA polymerase I, and ribosomal subunit assembly.

    Consequences of Genetic Rearrangements

    • Heterochromatin Rearrangements: Often silent because of the inactive state.
    • Euchromatin Rearrangements: Can disrupt genes or regulatory elements, causing diseases like cancer.

    Posttranslational Modifications and Complexes

    • Histone Modifications:
    • Acetylation (HATs): Activates transcription by loosening chromatin.
    • Methylation (HMTs): Can activate or repress transcription depending on the site.
    • Phosphorylation: Associated with chromatin condensation; and DNA repair.
    • Ubiquitination: Marks histones for remodeling or degradation.
    • Chromatin Remodeling Complexes: ATP-dependent complexes such as SWI/SNF, reposition or eject nucleosomes to allow access to DNA.

    Functional Parts of Chromosomes

    • Telomeres: Repetitive sequences (e.g., TTAGGG in humans) at chromosome ends, prevent degradation and ensure complete replication. Maintained by telomerase.
    • Centromeres: Region where kinetochores attach, enabling proper chromosome segregation during mitosis. Composed of heterochromatin and satellite DNA.

    DNA Replication and Repair

    • Replication Process: Semi-conservative, bi-directional, involves enzymes such as helicase, primase, DNA polymerase, and ligase. Leading strand is synthesized continuously, while lagging strand is synthesized discontinuously as Okazaki fragments, later joined by ligase.
    • PCR: Mimics DNA replication in a test tube; involves denaturation, annealing, and extension.

    Exam 2

    • Types of Chromatin in Eukaryotic Chromosomes: Euchromatin and Heterochromatin (facultative and constitutive).

    Exam 4

    • Ion and Solute Transport: Ions and solutes move across membranes via channels or transporters, depending on their properties and membrane permeability. Passive transport moves down concentration gradients, while active transport moves against gradients, requiring energy. Different types include channels, transporters (passive and active), symport, and antiport.
    • Electrochemical Gradient: The combined effect of concentration and electrical gradients, influencing ion movement.
    • Na+/K+ ATPase: A carrier protein, not a channel, that maintains the resting membrane potential by actively transporting 3 Na+ ions out and 2 K+ ions in.
    • Action Potentials: Initiated by depolarization and propagated along the membrane by the sequential opening and closing of voltage-gated Na+ channels.

    Additional Topics (Page 31 ff)

    • Inhibitory vs. Excitatory Neurons: Neurons can affect post-synaptic potentials (PSP) by altering membrane potentials. Excitatory neurons depolarize to increase the likelihood of action potentials; inhibitory neurons hyperpolarize.
    • Voltage-Gated Ca2+ Channels and Synaptic Vesicle Docking: Ca2+ influx through these channels into the presynaptic terminal triggers synaptic vesicle fusion to release neurotransmitters via exocytosis.

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    Test your knowledge on chromatin structure, types, and gene complexity in eukaryotic genomes. This exam covers nucleosomes, euchromatin, heterochromatin, and the organization of chromatin within the nucleus.

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