Final answer:
The mutation occurring when chromosomes don't separate properly during cell replication is called nondisjunction, leading to an abnormal number of chromosomes and potential physical and mental abnormalities. Different from point mutations affecting single nucleotides, nondisjunction concerns the entire chromosomes or chromatids.
Step-by-step explanation:
The mutation that occurs during cell replication when the chromosomes don't separate properly is known as nondisjunction. This chromosomal error happens when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in gametes with an abnormal number of chromosomes (aneuploidy). Nondisjunction can lead to several physical and mental abnormalities due to the consequential genetic imbalances. In contrast, other types of mutations such as point mutations affect single nucleotides, and frameshift mutations involve additions or deletions of nucleotides that shift the reading frame of the genetic code. On the other hand, errors in DNA replication during the S phase of cell division, if not repaired, could lead to various mutations including duplications, deletions, and translocations, some of which may alter an organism's phenotype or contribute to the development of diseases such as cancer.