During which cellular stage is a second chromatid containing a copy of DNA assembled?

During which cellular stage is a second chromatid containing a copy of DNA assembled?

• A. Interphase
• B. Prophase
• C. Metaphase
• D. Anaphase

Answer: (A)

DNA replication happens in the S phase of Interphase, the period when the cell doubles its DNA in preparation for division. During S phase, each chromosome is copied, producing two identical sister chromatids held together at the centromere. That second chromatid is the newly synthesized copy. After this, the cell proceeds through G2 and then mitosis, where those chromatids are eventually separated. The other mitotic stages involve organizing and separating the already replicated chromatids rather than making new copies, so they don’t produce a second chromatid.

DNA replication happens in the S phase of Interphase, the period when the cell doubles its DNA in preparation for division. During S phase, each chromosome is copied, producing two identical sister chromatids held together at the centromere. That second chromatid is the newly synthesized copy. After this, the cell proceeds through G2 and then mitosis, where those chromatids are eventually separated. The other mitotic stages involve organizing and separating the already replicated chromatids rather than making new copies, so they don’t produce a second chromatid.