Sex Determination and Differentiation-- Boy or Girl?

Concept: Review of the Sex Chromosomes

4m

Concept: Early Development and the Bipotential Genitals

4m

Concept: Feminization-- Becoming a Girl

2m

Concept: Masculinization-- Becoming a Boy

4m

Problem: A reproductive biologist is working at a start-up company that wants to let aspiring parents choose the sex of their child. This process will involve picking one sperm and one egg, doing in vitro (“in a dish”) fertilization, and then implanting the zygote in the mother-to-be. Which of the following gametes most directly determines the sex of the child and should be the focus of the biologist’s efforts?

2m

Problem: Turner Syndrome is an abnormality of the sex chromosomes where the patient has only one X chromosome and no 46th chromosome at all (i.e. they are “XO”). Which of the following describes the sex phenotype of a patient with Turner Syndrome (i.e. how are they likely to outwardly appear)?

3m

Problem: Klinefelter Syndrome is an abnormality of the sex chromosomes where the patient has two copies of the X chromosomes and one copy of the Y chromosome (i.e. they are “XXY” and have 47 chromosomes total). Which of the following describes the sex phenotype of a patient with Klinefelter Syndrome (i.e. how are they likely to outwardly appear)?

2m

Problem: A one-day old infant with two X chromosomes is found to have a blind vaginal pouch—that is, they have a normal-appearing external vagina that ends abruptly and lacks a normal vaginal canal. She does not have a uterus, Fallopian tubes, or ovaries. Which of the following structures failed to develop to cause this abnormality?

2m

Problem: Androgen Insensitivity is a sexual development disorder where an XY person makes testosterone but cannot respond to it. They can still respond to anti-mullerian hormone. What would an androgen insensitive baby’s genitals look like? (This is a really hard one—watch the video.)

4m