Practice question

Deletion removes genetic information, causing loss of coding sequences and regulatory elements, leading to haploinsufficiency or unmasking recessive alleles. No template remains to compensate. Duplication adds an extra copy of a segment; original information is retained, and dosage increase is often better tolerated because essential functions persist. Cells can inactivate, down-regulate, or evolve divergence of duplicate copies, reducing harm. While large duplications still disrupt dosage balance, viability is higher than comparable deletions, explaining prevalence of polymorphic copy-number variants in human genomes.