More DNA, more cells and a new cell state are different changes
Original home-study reading by Math-3Zs; AI-assisted authoring.
Chapter 5 background linking observations, mechanisms and model limits.
Read before this chapter and return after its investigation. All required teaching and supplied records are available locally. Source images have their own adjacent credits.
A replicated chromosome has two sister chromatids but is counted as one joined chromosome unit before their separation. Chromosome-set number, DNA-copy amount and cell number are separate. Typical mitosis preserves ploidy, while meiosis I separates homologs and meiosis II separates sisters after one replication.
Fertilization combines gamete sets. Early cleavage can partition existing material into more small cells without proportional whole-embryo growth. Later development coordinates division, movement, cell loss and differentiation. Four meiotic nuclear products are not always four equivalent mature gametes; organismal life cycles add distinct steps.
Differentiated cells can use shared sequence information differently through regulation and signaling. Counts, expression markers and specialized function are different evidence. Explain each stage with labeled chromosome/strand/state models, and state where a simplified case omits developmental variation, copying errors or changed conditions.
This explanatory prose is original. Source figures elsewhere retain their individual credits, links and reuse licenses.
Questions to carry into the chapter
How can division preserve information while reproduction and development produce differences?
Keep a first model, identify a measurable comparison and record a limitation to test.