1.) Human females have two X chromosomes in each cell. Which of the following is
ID: 165723 • Letter: 1
Question
1.) Human females have two X chromosomes in each cell. Which of the following is true of these chromosomes?
One chromosome is inactivated. The inactivated chromosome is always the one inherited from the father.
One chromosome is inactivated. The inactivated chromosome is always the one inherited from the mother.
Both chromosomes are active at all times.
2.) One of the chromosomes is inactivated. The process is random and results in cells that have either the mother's or the father's X chromosome active. Review the section "Investigating Life: Heredity and the Hungry Hordes."As indicated in the image below, the dominant allele (R) confers susceptibility to the Bt toxin, and a recessive allele (r) confers resistance to Bt. Suppose that a susceptible male mates with a resistant female. They have many offspring, a few of which are resistant to Bt. What is the genotype of the male parent, and what is the genotype of the susceptible offspring? (Assume complete dominance.)
The genotype of the male parent is Rr and the genotype of the susceptible offspring is either RR or Rr.
The genotype of the male parent is Rr and the genotype of the susceptible offspring is Rr.
The genotype of the male parent is either RR or Rr and the genotype of the susceptible offspring is either RR or Rr.
The genotype of the male parent is either RR or Rr and the genotype of the susceptible offspring is Rr.
The genotype of the male parent is RR and the genotype of the susceptible offspring is Rr.
Explanation / Answer
1. we know that one of the X-chromosomes of females is inactivated for dosage compensation. males have XY genotype. the single X-chromosome is active all the times.
Option A says that inactivated X-chromosome is inherited from father. Father has no inactivated X-chromosome. Then how can this be true? hence, option A-false.
Option B may be true
If Option C is true, there would be no concept of dosage compensation and X-chromosme inactivation. therefore, Option C- false.
2. given, the female parent is resistant. therefore, the genotype would be 'rr'. if the male parent is 'RR' all the offsprings would 'Rr', i.e, only susceptible. But this is not the case. some of the offsprings are resistant whereas some are susceptible.
therefore, male parent must be 'Rr'. if male parent is 'Rr', offsprings would be 'Rr' (susceptible) and 'rr' (resistant)
hence, option B is true.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.