A Chromosome Duplication Is a Mutation That Doubles Part of a Chromosome

A chromosome duplication is a mutation that doubles part of a chromosome. In individuals heterozygous for a chromosome duplication, the duplicated region of the chromosome loops out when homologous chromosomes pair in prophase I of meiosis. Duplications often have major effects on the phenotype, possibly by altering gene dosage. Segmental duplications are common within the human genome.
-Chromosome duplications often result in abnormal phenotypes because

A) developmental processes depend on the relative amounts of proteins encoded by different genes.
B) extra copies of the genes within the duplicated region do not pair in meiosis.
C) the chromosome is more likely to break when it loops in meiosis.
D) extra DNA must be replicated, which slows down cell division.