Chapter 10: Problem 55
What is the relationship between control of DNA synthesis in eukaryotes and the stages of the cell cycle?
Short Answer
Expert verified
DNA synthesis occurs in the S phase and is regulated by checkpoints in the G1 and G2 phases, ensuring proper conditions and accurate replication.
Step by step solution
01
Identify the Phases of the Cell Cycle
The cell cycle in eukaryotes consists of four main phases: G1 (Gap 1), S (Synthesis), G2 (Gap 2), and M (Mitosis).
02
Explanation of S Phase
During the S phase, DNA synthesis occurs. This phase is crucial because it ensures that each daughter cell will have a complete set of DNA after cell division.
03
Control Mechanisms in G1 Phase
The G1 phase includes a checkpoint that determines whether the cell has the necessary resources and conditions to proceed to the S phase. If conditions are not favorable, the cell cycle is halted.
04
G2 Phase and Its Control Mechanisms
The G2 phase also contains regulatory checkpoints to ensure that DNA synthesis in the S phase has been completed correctly, and repairs any DNA damage before the cell enters mitosis.
05
M Phase
The M phase involves the separation of copied chromosomes into two daughter cells. Successful completion of DNA synthesis in S phase is critical for accurate chromosome segregation.
06
Overall Relationship
Control of DNA synthesis in eukaryotes is tightly linked to the regulation of the cell cycle via checkpoints in G1, S, and G2 phases. These checkpoints monitor and ensure that conditions are suitable and that DNA is accurately replicated before cell division.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Phases of the Cell Cycle
The cell cycle is a series of stages that eukaryotic cells go through to divide and produce new cells. The phases include:
- G1 Phase (Gap 1): The cell grows and synthesizes proteins.
- S Phase (Synthesis): DNA replication occurs, making identical copies of each chromosome.
- G2 Phase (Gap 2): The cell continues to grow and prepares for mitosis.
- M Phase (Mitosis): The cell divides its copied DNA and cytoplasm, resulting in two daughter cells.
Regulatory Checkpoints
Regulatory checkpoints are crucial control mechanisms that ensure the integrity of the cell cycle.
- G1 Checkpoint: This checks whether the cell has enough energy and materials to proceed to the S phase.
- G2 Checkpoint: Ensures that DNA has been correctly replicated and repairs any DNA damage before the cell enters mitosis.
- M Checkpoint: Ensures that all chromosomes are correctly attached to the mitotic spindle before proceeding with division.
Eukaryotic Cell Division
Eukaryotic cell division involves a series of carefully regulated stages. Starting from the G1 phase, where the cell grows, it then enters the S phase to replicate DNA. After another growth and preparation phase (G2), the cell then undergoes mitosis (M phase), ultimately producing two genetically identical daughter cells. The replication and division process is meticulously regulated to ensure accuracy and prevent mutations.
G1 Phase
The G1 phase is the stage where the cell increases in size and synthesizes various enzymes and nutrients necessary for DNA replication. It also contains a critical checkpoint where the cell evaluates whether it has the resources to proceed to DNA synthesis. If conditions are unfavorable, the cell can enter a resting state known as G0 phase or attempt to repair any issues before moving forward.
S Phase
The S phase is the part of the cell cycle where DNA replication occurs. Each chromosome is duplicated to ensure that both daughter cells will inherit a full set of DNA. This phase is vital as it ensures each daughter cell receives an identical set of genes. The accuracy of DNA replication is crucial, and cells employ proofreading and repair mechanisms to ensure replication fidelity.
G2 Phase
During the G2 phase, the cell continues to grow and prepare for mitosis. At this stage, the G2 checkpoint plays a critical role by ensuring that DNA replication in the S phase was completed accurately. If any DNA damage or errors are detected, the cell will attempt to repair them before proceeding to mitosis. This helps to ensure that the resulting daughter cells will be free from genetic defects.
M Phase
The M phase, also known as mitosis, is where the cell divides its replicated DNA and cytoplasm into two daughter cells. This phase is divided into several stages:
- Prophase: The chromosomes condense and the nuclear envelope begins to dissolve.
- Metaphase: Chromosomes line up at the metaphase plate.
- Anaphase: Chromatids are pulled apart to opposite ends of the cell.
- Telophase: Nuclear membranes re-form around the separated chromatids.
DNA Replication
DNA replication is an essential process that occurs during the S phase. This ensures that each daughter cell will have an exact copy of the genetic material. The process involves:
- Initiation: Unwinding of the double helix and formation of replication forks.
- Elongation: DNA polymerase synthesizes new strands by adding nucleotides complementary to the template strands.
- Termination: Completion of DNA synthesis and disassembly of replication machinery.