Match chromosome arrangements with mitotic stages and order division events.
Method and worked examples
In the standard simplified mitotic sequence, chromosomes condense during prophase. At metaphase, duplicated chromosomes align at the cell equator. Sister chromatids separate towards opposite poles in anaphase. During telophase, nuclear envelopes form around the separated chromosome sets and chromosomes begin to decondense. Use the arrangement described, rather than cell size, to identify a stage.
Interphase precedes mitosis and includes DNA replication during S phase. Replication supplies sister chromatids; anaphase distributes them. Cytokinesis divides cytoplasm and may overlap the final stages of mitosis. A snapshot count records the proportion of observed cells in each stage. It does not by itself show the exact duration of a stage without further assumptions about the population.
Example 1
Duplicated chromosomes are lined up at the centre of a cell. Identify the stage.
Metaphase: duplicated chromosomes align at the equator before sister chromatids separate.
Example 2
Of 120 observed cells, 30 are in metaphase. Calculate the metaphase percentage.
12030×100=25% of the observed cells.
Watch out:DNA is copied during S phase before mitosis; anaphase separates the sister chromatids already produced.
Identifying mitotic stages | Year 11 Biology | Ascent Arcade