Question

19 use the scenario to answer the following question. a couple gives birth to a healthy baby girl. as the girl grows and develops, they find out she has turner’s syndrome, which means that she is missing an x chromosome. the family is trying to understand the cause. which of the following choices provide the best explanation for how the girl inherited turner’s syndrome? (aks 7c) a during meiosis, nondisjunction occurred, and the sex chromosomes did not separate evenly into gametes of one parent. b the mother and father both carried a recessive allele which were then passed to the daughter. c the mother was exposed to a mutagen during early pregnancy that altered the genotype of her daughter. d during crossing over, the x chromosome recombined genes and traits were lost during the process.

Explanation:

Turner’s Syndrome (XO) results from a missing X chromosome, caused by nondisjunction during meiosis (when gametes form, chromosomes fail to separate evenly). Option B is incorrect as Turner’s is not a recessive allele - based disorder. Option C is wrong because mutagen exposure would cause mutations, not chromosome loss. Option D is incorrect as crossing - over (gene recombination) doesn’t cause chromosome loss. Only Option A explains the chromosome - level error (nondisjunction) leading to Turner’s.

Answer:

A. During meiosis, nondisjunction occurred, and the sex chromosomes did not separate evenly into gametes of one parent.