Sex-linked inheritance

Question 1

T/F: the selection process for which X chromosome remains active appears to be a random process

Answer 1

True

Question 2

The ___ gene encodes an ___ that binds to and inactivates the X chromosome

Answer 2

XIST

RNA

Question 3

Barr body

Answer 3

-the inactivated X chromosome that is visible in the interphase nucleus

Question 4

how many Barr bodies are present in XXXXY

Answer 4

3 Barr bodies will be present

Question 5

what explains the difference in fluorescent-antibody staining for dystrophin in females and males with muscular dystrophy?

Answer 5

dystrophin is located on the X chromosome. In heterozygotous females, random Lyonization will lead to help debilitating disease

Question 6

45, X

Answer 6

Turner Syndrome

Question 7

Do most Turner conceptuses make it to full term?

Answer 7

No, 99% conceptuses spontaneously abort

Question 8

47, XXY

Answer 8

Klinefelter syndrome

Question 9

how many Barr bodies will be present in Klinefelter syndrome?

Answer 9

1 Barr body

Question 10

What process went wrong to lead to XYY?

Answer 10

paternal nondisjunction at meiosis 2

Question 11

a female patient of yours presents with 2 Barr bodies, what condition is present? What is the prognosis for fertility? For IQ performance?

Answer 11

• Trisomy X (47,XXX)
• fertility will be normal
• deficit performance on IQ test

Question 12

XXYY syndrome is closely related to what other sex-linked disorder?

Answer 12

-Klinefelter’s