Cell cycle and DNA content
A chromosome is counted by its centromere. After S phase, each replicated chromosome has two sister chromatids. Ploidy describes sets of homologous chromosomes, whereas DNA content describes DNA amount. A diploid G2 cell remains diploid even though it has twice its G1 DNA. Some differentiated cells enter a nondividing state called G0. Interphase includes G1, S, and G2 and is often the largest part of the cycle.
MAKE IT CONCRETE
A cell with 2n = 8 has 8 chromosomes and 16 chromatids in G2. After a normal mitosis and cytokinesis, each daughter has 8 chromosomes.
DON’T FALL FOR THIS
Twice the DNA does not automatically mean twice the ploidy. Chromatids and homologous chromosomes are different relationships.