2. LMS is very rare human hereditary disorder resulting in spastic para parapleg

Question

2. LMS is very rare human hereditary disorder resulting in spastic para paraplegia and mental retardation. LMS is caused by a recessive allele with Mendelian inheritance. A couple, Ross and Rachel would like to have children. However, Ross’s great-great grandfather was known to have had a daughter(from a previous marriage, not with Ross’s great-great grandma) who suffered from LMS. Rachel has a brother who has LMS. Now, Ross and Rachel are considering having a child.

a. Draw a pedigree of the above family.
b. What is the prob. that Ross and Rachel's first child with also have LMS?

Explanation / Answer

The bad allele is X linked.

Rachel's pedigree would look something like this:

Rachel's mother    Rachel's Father

X(BadX) XY

Rachel               Rachel's Brother

XX                              (Bad X) Y

There is really no chance that Rachel's side would have the bad allele because she received two good XXs.

I don't know if there is enough information to tell Ross's side but it seems like the other great great grandmother had the bad allele.

I think there is slim chance of the their child getting the bad allele because Ross does not have LMS. Women can carry it and not be affected because they have another good X but men do not.

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.