Question

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.

Answer 1

In the case of an XXY offspring with Klinefelter Syndrome exhibiting a pointed nose, a nondisjunction event in one of the parents during gametogenesis caused the condition, with a carrier parent providing the recessive allele for the pointed nose.

Step-by-step explanation:

The question revolves around a genetic nondisjunction event that leads to Klinefelter Syndrome (XXY) and the inheritance of an X-linked trait for nose shape, where round nose is dominant over pointed nose. Considering that both XY parent with a round nose and XX parent with a round nose have produced an XXY offspring with a pointed nose, we can infer that one parent must have carried at least one X chromosome with a recessive allele for a pointed nose (Xp). The occurrence of Klinefelter Syndrome suggests a nondisjunction event during gametogenesis in one of the parents. Nondisjunction might have happened in the father during meiosis I, where both X and Y chromosomes went to the same sperm, or in the mother when the two X chromosomes failed to separate, leading to an egg with two X chromosomes, one of which carried the recessive allele (XpX).

Answer 2

Step-by-step 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.