Sex-influenced traits are expressed

Please just explain the correct answer! Thank you! I will rate.Sex-influenced traits are expressed______________

  • as a result of genes on the X chromosome.
  • after the formation of a Barr body.
  • as a result of hormone differences between males and females.
  • more in males than females.
  • more in females than males

Tamryn has a son who has Duchenne muscular dystrophy, which is inherited as an X-linked recessive trait. At a molecular level, the disease is due to lack of the protein dystrophin. Tamryn participates in a study to look at dystrophin levels in various muscles, so has cells sampled from 10 different muscles. Some cells make dystrophin, and some do not. An explanation for this finding is that

  • the X chromosome that bears the mutation is turned on in some cells but inactivated in others
  • Tamryn is making less dystrophin as she gets older. The study should be repeated at different ages.
  • the mutation originated in the son
  • Tamryn does not have a Y chromosome
  • the mutation is only present in some muscle cells.

Very rarely, one member of a pair of identical (monozygotic) twins will have Turner syndrome (XO) and the other member will be normal (XX). Which of the following statements best explain this phenomenon.

  • Dad’s X chromosome was inactivated, causing Turner syndrome.
  • there was a non-disjunction event during meiosis in either parent
  • There was a non-disjunction event during mitosis in the zygote.
  • There was a non-disjunction event during meiosis in dad.
  • There was a non-disjunction event during meiosis in mom.
 
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