In this chapter, we focused on how chromosomes are distributed during cell division, both in dividing somatic cells (mitosis) and in gamete- and spore-forming cells (meiosis). We found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, answer the following questions. How do we know that DNA replication occurs during interphase, not early in mitosis?

Key Concepts

DNA Replication

DNA replication is the process by which a cell duplicates its DNA before cell division. This occurs during the S phase of interphase, ensuring that each daughter cell receives an identical set of chromosomes. Understanding the timing of DNA replication is crucial for distinguishing between interphase and mitotic phases.

Cell Cycle Phases

The cell cycle consists of several phases: interphase (which includes G1, S, and G2 phases) and mitosis. Interphase is the period when the cell prepares for division, including DNA replication, while mitosis is the actual division of the cell's nucleus. Recognizing these phases helps clarify when DNA replication occurs.

Experimental Evidence

Experimental evidence, such as pulse-chase experiments and labeling techniques, has shown that DNA synthesis occurs during interphase. These methods allow scientists to track the incorporation of nucleotides into DNA, confirming that replication is completed before mitosis begins, thus providing a clear distinction between these processes.