Question

Lesch-Nyhan syndrome is an X-linked, recessive condition caused by mutation of the HPRT1 gene responsible for purine metabolism. The syndrome is characterized by juvenile-onset gout, involuntary muscle movements, and behavioral disorders. A mother and father have a young daughter who was diagnosed with Lesch-Nyhan syndrome. No one in the father\'s family was ever diagnosed with the syndrome. The mother\'s maternal grandfather was diagnosed with Lesch-Nyhan syndrome, but neither one of her parents was diagnosed with the condition. Select all the descriptions that could explain how their daughter inherited Lesch-Nyhan syndrome.
A.The mother's X chromosomes failed to separate during meiosis, and the daughter inherited two X chromosomes with the Lesch-Nyhan mutation. The father contributed no sex chromosomes.

B. The father did not contribute a sex chromosome to his daughter due to nondisjunction of the sex chromosomes. The daughter is XO and her only X chromosome came from her mother, who was a carrier.

C.The daughter could not have inherited Lesch-Nyhan because neither of her parents have the disease. The fact that her great-grandfather had Lesch-Nyhan is a coincidence.

D. The daughter is XO. Her only X chromosome carries the Lesch-Nyhan mutation and was inherited from her father, who was a carrier.

Answer 1

Answer:

B. The father did not contribute a sex chromosome to his daughter due to nondisjunction of the sex chromosomes. The daughter is XO and her only X chromosome came from her mother, who was a carrier.

A.The mother's X chromosomes failed to separate during meiosis, and the daughter inherited two X chromosomes with the Lesch-Nyhan mutation. The father contributed no sex chromosomes.

Explanation:

As seen in the question above, a little girl was diagnosed with Lesch-Nyhan syndrome, which is an X-linked recessive condition caused by a mutation in the HPRT1 gene responsible for purine metabolism.

The little girl's parents do not have the syndrome, and no one in the little girl's paternal family presented this syndrome, however, we know that the maternal grandfather of the little girl's mother had the syndrome, which means that it was the mother's genetic material that contributed to the development of the syndrome in the little girl. This was because the little girl did not receive any X chromosomes from her father, but she inherited the two X chromosomes from her mother that coded for the Lesch-Nyhan mutation. This happened because the mother's X chromosome disjuction did not occur during meiosis I.

As shown above, the father did not contribute any sex chromosomes to his daughter, which means that the daughter is XO and her only X chromosome came from her mother, who was a carrier.