One Similarity Between Mitosis and Meiosis: Both Start With One Diploid Parent Cell That Replicates Its DNA

Mitosis and meiosis share a fundamental beginning: both start with one diploid parent cell that replicates its DNA before dividing. A diploid cell contains two complete sets of chromosomes (one from each parent), and in both processes that cell copies its genome during the S phase of interphase. This shared starting point is one similarity between mitosis and meiosis, even though the two processes end very differently — mitosis produces two identical diploid cells, while meiosis produces four genetically unique haploid cells.

Shared Diploid DNA Replication Start

In both mitosis and meiosis, the journey begins with a single diploid parent cell. “Diploid” means the cell carries two copies of each chromosome — in humans, that’s 46 chromosomes, arranged as 23 pairs. Before any division happens, that cell must duplicate its DNA so each future daughter cell gets a complete set of instructions.

That duplication step is identical in both processes. The DNA is copied during interphase, specifically the S (synthesis) phase, according to Nature Education (Scitable). At the end of replication, the cell has duplicated chromosomes, each consisting of two sister chromatids joined at a centromere.

For example, a human cell entering either process has 46 chromosomes; after S phase, it still counts 46 chromosomes but holds 92 chromatids. The chromosome number doesn’t change yet — only the amount of DNA doubles.

How This Similarity Works

The replication event is the same molecular process in both cases. Enzymes unwind the double helix, and each strand serves as a template to build a complementary strand, a mechanism described by the National Center for Biotechnology Information. The result is two identical sister chromatids for every chromosome.

What differs is what happens after replication. Mitosis separates sister chromatids once, producing two diploid cells that are genetically identical to the parent. Meiosis undergoes two rounds of division (meiosis I and II), producing four haploid cells with half the chromosome number. So the shared S phase is the common launchpad; the divergence comes later in how the chromosomes are sorted and how many times the cell divides.

Key Takeaways

• Both mitosis and meiosis begin with one diploid parent cell that replicates its DNA during the S phase of interphase.
• DNA replication produces identical sister chromatids in both processes — the chromosome number stays the same, but DNA content doubles.
• The processes diverge after replication: mitosis yields two identical diploid cells; meiosis yields four genetically varied haploid cells.
• That shared replication start is the key similarity, even though the two processes finish very differently.