Passage of information from parents to offspring — practice question

During meiosis, homologous chromosomes can sometimes fail to separate at anaphase. This is called non-disjunction. Turner’s syndrome is the most common chromosome mutation in human females. It may arise because of non-disjunction in meiosis during gametogenesis. As a result, some gametes lack an X chromosome. In other cases of Turner’s syndrome, one chromosome from the X pair is not missing, but it is damaged instead. The damaged X chromosome may have broken and then rejoined, so that part of its structure has been lost. Fig. 7.1 shows a normal X chromosome together with two ‘damaged’ X chromosomes, $X_1$ and $X_2$. For $X_1$, part of the ‘p’ arm of the chromosome is absent. This deletion causes the female to have reduced height and abnormalities such as narrowing of the aorta. For $X_2$, part of the ‘q’ arm of the chromosome is absent. This deletion causes little or no development of the ovaries.