The gene for nose shape is found on the X chromosome. Round nose is dominant to pointed nose. Human individuals with XXY (an additional X chromosome) are designated male. Individuals with XO (only one X chromosome) are designated female. Identify the possible nondisjunction events (rare mistakes during meiosis) that could explain the phenotype of the offspring. An XY parent with a round nose and a XX parent with a round nose have an offspring with Klinefelter Syndrome (genotype XXY) with a pointed nose.

Explanation:

in this case female parent XX is hetrozygous for round nose. when a cross between round nose father XY and hetrozygous round nose mother takes place and suddenly a chromosomal nondisjuction occurs, the chromosomes carrying genes for pointed tip nose come togather in a gamete and a gamete (egg) with XX chromosomes is appeared having 24 chromosomes instead of 23. when this gamete fertilizes with a sperm having normal 23 chromosomes and only carry Y chromosomes, a pointed nose klienfelter syndrome case will appear.

as in mitosis, dna replication occurs during interphase.   in meiosis, it occurs specifically in s phase of interphase 1.