Which of the following occurs during S phase?(A) condensation of the chromosomes(B) replication of the DNA(C) separation of sister chromatids(D) spindle formation

Verified step by step guidance

1. Understand the cell cycle phases: The cell cycle consists of interphase (G1, S, G2) and mitotic phase (M).
2. Identify the S phase: The S phase, or synthesis phase, is part of interphase where specific cellular activities occur.
3. Recall the main event of the S phase: During the S phase, the cell replicates its DNA to ensure that each daughter cell will have a complete set of chromosomes.
4. Differentiate between the options: (A) condensation of the chromosomes occurs during prophase of mitosis, (B) replication of the DNA occurs during the S phase, (C) separation of sister chromatids occurs during anaphase of mitosis, (D) spindle formation begins in prophase of mitosis.
5. Conclude that the correct answer is the option that describes the replication of DNA, which is the primary event of the S phase.

Key Concepts

S Phase of the Cell Cycle

The S phase, or synthesis phase, is a crucial part of the cell cycle where DNA replication occurs. During this phase, each chromosome is duplicated, resulting in two sister chromatids for each chromosome, which are essential for cell division. Understanding the S phase is vital for grasping how genetic information is passed on during cell division.

DNA Replication

DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. This process is essential for cell division, ensuring that each daughter cell receives an exact copy of the parent cell's genetic material. Key enzymes, such as DNA polymerase, play a significant role in this process, making it a fundamental concept in genetics.

Chromosome Structure

Chromosomes are structures within cells that contain DNA and proteins. During the S phase, chromosomes are not yet condensed; they exist in a less compact form, allowing for the replication process. Understanding chromosome structure is important for recognizing how genetic material is organized and how it behaves during cell division.