Analyze the mutation

Claim: The change shown in the karyotype model is a whole-chromosome error that could seriously affect development.\n\nEvidence: In the model, chromosome 21 appears three times instead of the normal pair, so the cell carries 47 chromosomes rather than 46. Every other chromosome pair looks typical, and no single band or gene was rewritten.\n\nReasoning: The severity of a genetic change depends on how much genetic material is added or lost and how many genes that touches. An extra copy of an entire chromosome means hundreds of genes are present in three doses instead of two, which raises how much of each protein the cell makes. Because so many genes are affected at once, this whole-chromosome error tends to have broad, body-wide effects rather than one narrow change, and a trisomy of chromosome 21 is consistent with a diagnosis of Down syndrome. This differs from a change that swaps or deletes a single base, which alters at most one gene. A limitation is that a karyotype shows chromosome number and shape but not how active each gene is, so the model can suggest that an effect is likely but cannot show exactly which traits will appear or how strongly.