what stages of mitosis does a single chromatid constitute an entire chromosome?

Answer 1

Well each chromatid contains all the genes, when the cell is prparing for mitosis or meiosis, DNA replication takes place and makes the sister chromatids (chromosomes). And during Anaphase, the chromosomes are separated by the mitotic spindle and taken to opposite ends of the cell.

In other words, before mitosis, the cells contain chromatids until DNA replication. During mitosis the sister chromatids are separated at anaphase. When the daughter cells separate after telophase, each cell has chromatids. A single chromatid is NOT a chromosome. A chromosome is sister chromatids.