Problem 6 - Biology Today and Tomorrow with Physiology

Question

Interphase is the part of the cell cycle when __________. a. a cell ceases to function b. a cell forms its spindle apparatus c. a cell grows and duplicates its DNA d. mitosis proceeds

Step-by-Step Solution

Answer

It's the phase when a cell grows and duplicates its DNA; option c is correct.

Step 1: Understanding Interphase

Interphase is a phase of the cell cycle where the cell prepares for mitosis. It comprises the majority of a cell's life cycle and involves several key processes critical for cell division.

Step 2: Analyzing the Options

Let's review the options: - a) A cell ceases to function: During interphase, cells are active, not ceasing to function. - b) A cell forms its spindle apparatus: The assembly of spindle fibers occurs during mitosis, not interphase. - c) A cell grows and duplicates its DNA: This is a critical function of interphase; during this phase, the cell grows, carries out normal functions, and duplicates its DNA. - d) Mitosis proceeds: Mitosis is the phase following interphase, where the actual cell division occurs.

Step 3: Selecting the Correct Answer

The correct description of interphase is that it is the phase when a cell grows and duplicates its DNA. This preparation is necessary for the subsequent mitotic phase.

Key Concepts

Cell Cycle

The cell cycle is an essential process that allows cells to grow, replicate, and ultimately divide. It consists of several phases, orchestrating the life and reproduction of a cell. The main phases are:

• Interphase: This is where the cell spends most of its life. It prepares for cell division by performing its normal functions, growing, and replicating its DNA.
• Mitosis: The phase of actual cell division, where the cell splits into two daughter cells.
• Cytokinesis: Following mitosis, this is the process that completes cell division by dividing the cytoplasm and cell membrane.

Interphase can be further broken down into three sub-phases: G1, S, and G2.

- The G1 phase is where the cell exhibits significant growth. - The S phase, or synthesis phase, is crucial for DNA replication. - The G2 phase involves final preparations for mitosis, including additional growth and protein synthesis. Understanding the cell cycle is fundamental for grasping how living organisms grow and reproduce. Each phase plays a pivotal role in ensuring that new cells are precise copies of the original.

DNA Replication

DNA replication is a vital process that happens during the S phase of interphase. It ensures that each daughter cell receives an exact copy of the parent cell's DNA, essential for maintaining genetic continuity across generations.

This process begins when the double-stranded DNA unwinds to form two separate strands.
Specialized enzymes called helicases break the hydrogen bonds between base pairs, allowing each strand to serve as a template for the new DNA molecules. New nucleotides are then added to each template strand by an enzyme known as DNA polymerase.

• Each nucleotide pairs with its complementary base (adenine with thymine, and cytosine with guanine).
• This results in two DNA molecules, each consisting of one old strand and one new strand, a process referred to as "semiconservative replication."

DNA replication is a highly accurate process, though errors can occur, leading to mutations. Cells have various mechanisms to repair these errors, ensuring the fidelity of genetic information.

Cell Growth

Cell growth is a fundamental aspect of the cell cycle, primarily occurring during interphase.

During the G1 phase, cells increase in size and synthesize proteins and organelles in preparation for DNA replication. This phase is crucial for cells to reach a size that is suitable for division.

• Nutrient Availability: Adequate nutrients and energy are crucial for cell growth.
• Signal Molecules: Growth factors and hormones can regulate and stimulate cell growth.
• Size Checkpoints: Before proceeding to the S phase, cells must pass growth checkpoints, ensuring they have grown sufficiently.

Besides growth in size, cells during this phase are also involved in regular metabolic activities, contributing to the overall maintenance and functioning of the organism. Proper cell growth is essential for healthy development and function of tissues and organs.