Help Kaplan BIochemistry Question.

[Mixmaster]

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HI,
I was looking through the Kaplan Biochem notes and I cannot figure out an answer. THe question is on page 121 of the Genetic Testing chapter 7 question 5 about the parents and the kid with sickle cell. Is there a mistake? I guess you need the book to be able to answer since the answers are dot blots.
THanks

 

[Row Jimmy]

I don't have the book with me at the moment but I think I remember the question. In a Dot Blot they have 3 sets of 2 blots. The 2 blots are ASO probes for Sickle Cell and Normal respectively. I think the Kid has Sickle Cell trait b/c he will show a positive blot in both the Sickle Cell and Normal blots.

The Kid should show up with a color change (black in Kaplan) in both blots.

I hope we are talking about the same question.

RJ

 

[Mixmaster]

Mom is PHENOTYPICALLY normal. Dad has Sickle Cell. Kid heterozygous. What should it look like?



My guess (disease is recessive right?)
Mom no dots or 1 dot, Dad dot on the sickle probe, fetus dot on both probes.

Answer in book
Mom dot on sickle probe only; Dad dot on both probes; Fetus dot on sickle probe only. <I dont get it>

 

[Idiopathic]

Fetus has to have exactly what mom has, no matter how the rest of it looks, since both are heterozygous. That right there probably gives the answer.

edit: if mom has only one dot, then it means that normal has no corresponding dot, and therefore, the fetus could only have one dot.

 

[Mixmaster]

You know I think there is an error in the book cuz answer B and C are the exact same and C is the answer?????

Idio--- but if mom is phenotypically normal then she could be
homozygous dominant(normal non-carrier)
or
heterozygous (carrier; but phenotypically normal)
but child is heterozygous. So not necessarily the same dots. Am I right?

 

[djs002]

2002 ed. of the book, C is correct: Mom normal probe only, father sickle probe only, kid both probes. In fact C is the only choice in which the father has only the sickle probe, which is a necessity since he has sickle disease.

Why haven't I sold these books already?

 

[Idiopathic]

You know I think there is an error in the book cuz answer B and C are the exact same and C is the answer?????

Idio--- but if mom is phenotypically normal then she could be
homozygous dominant(normal non-carrier)
or
heterozygous (carrier; but phenotypically normal)
but child is heterozygous. So not necessarily the same dots. Am I right?

Thats true, I didnt catch that. The problem is mom has a 50% chance of being heterozygous or homozygous and that is too much chance to base the question on. Like the above poster said, there must be a fatal flaw in the answer choices or a typo somewhere.