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G1 Phase quiz #1

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  • What is the primary function of the G1 phase in the cell cycle, and why is the transition from G1 to S phase tightly regulated?
    The G1 phase is a growth phase where the cell prepares for division by increasing in size and synthesizing necessary components. The transition from G1 to S phase is tightly regulated by the start checkpoint to ensure the cell is ready for DNA replication; if the cell is not properly prepared, entering S phase can lead to cell death or inadequate division.
  • How do mitogens influence the progression of the cell cycle during the G1 phase?
    Mitogens are extracellular signals that stimulate cell growth by activating cyclins and cyclin-dependent kinases (CDKs) specific to G1 phase, while inhibiting S and M phase cyclins to ensure the cell grows sufficiently before DNA replication and division.
  • What role does the protein p53 play during the G1 phase, and how does it contribute to cancer prevention?
    p53 is a transcription regulator that halts the cell cycle in G1 if DNA damage is detected, allowing time for repair. If the damage is irreparable, p53 can trigger apoptosis. This function prevents cells with damaged DNA from dividing, thereby helping to prevent cancerous growth.
  • What happens to a cell if it detects irreparable DNA damage or is otherwise unprepared for division during G1 phase?
    If a cell detects irreparable DNA damage or is unprepared for division during G1 phase, it may enter G0, a non-dividing state, where it can attempt repair or remain inactive until conditions improve.
  • What initiates DNA replication at the end of G1 phase, and what is the role of S cyclin-dependent kinases (SCDKs)?
    At the end of G1 phase, S cyclin-dependent kinases (SCDKs) are activated, which initiate DNA replication by activating DNA helicases and promoting the formation of the pre-replicative complex at origins of replication.
  • What is the main purpose of the G1 phase in the cell cycle, and why is the transition to S phase carefully controlled?
    The G1 phase allows the cell to grow and prepare for division by synthesizing necessary components. The transition to S phase is tightly regulated by the start checkpoint to ensure the cell is ready for DNA replication, as premature entry can lead to cell death or improper division.
  • How do mitogens affect the cell during the G1 phase?
    Mitogens are extracellular signals that stimulate cell growth by activating G1-specific cyclins and cyclin-dependent kinases (CDKs), while inhibiting S and M phase cyclins to ensure the cell grows sufficiently before DNA replication.
  • What is the function of the protein p53 during the G1 phase, and how does it help prevent cancer?
    p53 halts the cell cycle in G1 if DNA damage is detected, allowing time for repair or triggering apoptosis if the damage is irreparable. This prevents cells with damaged DNA from dividing, reducing the risk of cancerous growth.
  • What happens to a cell in G1 phase if it detects irreparable DNA damage or is otherwise unprepared for division?
    The cell may enter G0, a non-dividing state, where it can attempt repair or remain inactive until conditions improve.
  • What triggers the initiation of DNA replication at the end of G1 phase, and what is the role of S cyclin-dependent kinases (SCDKs)?
    Activation of S cyclin-dependent kinases (SCDKs) triggers DNA replication by activating DNA helicases and promoting the formation of the pre-replicative complex at origins of replication.
  • What occurs during the G1 phase of the cell cycle?
    During the G1 phase, the cell grows, synthesizes proteins and organelles, and prepares for DNA replication and division. It is regulated by the start checkpoint and influenced by mitogens.
  • What is the major event happening to a cell during G1 phase?
    The major event during G1 phase is cell growth and preparation for DNA replication.
  • The growth phase of the cell cycle is known as which phase?
    The growth phase of the cell cycle is known as the G1 phase.
  • What is the cell doing in the G0 phase?
    In the G0 phase, the cell is in a non-dividing, quiescent state where it may repair itself or remain inactive until conditions are favorable for division.
  • In what stage is a cell before mitosis begins?
    Before mitosis begins, a cell is in interphase, which includes the G1, S, and G2 phases.
  • What happens in the G0 phase of the cell cycle?
    In the G0 phase, cells exit the active cell cycle and enter a resting state, where they do not divide but may perform normal cellular functions or repair.
  • What type of cell typically enters the G0 phase?
    Cells that do not regularly divide, such as nerve cells, typically enter and remain in the G0 phase.
  • What happens in G1 of the cell cycle?
    In G1, the cell grows, produces proteins and organelles, and prepares for DNA replication.
  • What is the G0 phase of the cell cycle?
    The G0 phase is a non-dividing state where cells can remain temporarily or permanently, often to repair or because they do not need to divide.
  • What cell structures are made in G1?
    During G1, the cell synthesizes proteins and organelles needed for growth and future cell division.
  • What is a cell doing during the G1 and G2 periods?
    During G1 and G2, the cell is growing, synthesizing proteins and organelles, and preparing for DNA replication (G1) or mitosis (G2).
  • What role does the protein p53 play during the G1 phase?
    During G1, p53 halts the cell cycle if DNA damage is detected, allowing for repair or triggering cell death if the damage is irreparable.