FCD Q&As
Here is an example of how to obtain answers to posted questions. Try them out, figure out where you got stuck, post (in the comments, for example) what you got done and what you are confused about, and help will be right on its way...
posted by pam39 @ 2:24 PM
12 Comments:
Finally, I GOT IT!!
Hi, glad you figured it out. I was kicking myself when I figured out the morphs.
I hope others will post and discuss their answers, too.
Happy studying.
Hey Pam,
Just a suggestion: maybe on the blog..you can divide 4 different sections for us to post questions. For example, one heading for Dr. Beatty's material, one for Dr. Doheny and one for Dr. Haugh.. and one heading to ask about the questions you gave us for practice, that way it'll be more organized because we'll get a lot of postings and it'll be confusing to read them :S
But of course it would have to depend on us to post it in the correct heading!
Just an idea...doesn't have to be played out if it's stupid =)
I still don't understand this q...how do we know whether the kid will be able to cook or not? There are two differnt morphs that show dieseased individuals, so when u look at the kid how will u determine it?
where did this question come from? are there other questions floating around?
This comment has been removed by the author.
Individuals I-3 and I-4 BOTH have the same RFLP mapping but different phenotypes, and they're both from the same family. I'm confused...
Wait, forget the last post. Is the answer that the baby girl WILL be able to cook (ie: unaffected)? Is the genotype of the unknown affected male either top/top or top/bottom?
Wait, why do we say that since you said it was rare, the condition was dominant. If it was dominant, wouldn't the disease infiltrate throughout the population and the disease will no longer be rare?
Why is it highly unlikely to have lots of carriers for a rare condition? To me, that would make more sense because unless the carriers get together and have the 0.25 chance of a homozygous recessive, it's pretty rare...
I don't understand how two families can have the same mutation phenotypically, but geneotypically the way in which the mutation came about it completely differnt? How does that work?
The two families DO have the same mutation genotypically. However, in this specific case, the mutation that gives the FCD phenotype is NOT what generates the presence/absence of a restriction site.
RFLPs are POLYMORPHISMS, meaning that they are not rare. Maybe the "2 bands" morph has a 40% frequency in the population, while the "1 band" has 60%. However, VERY FEW people have the FCD mutation (maybe less than 1%). In the first family, the first germ cell in which the FCD mutation occurred (many generations ago) happened to have the "2 bands" morph.So, in that family, whoever gets the FCD mutation also gets the "2 bands" morph for our RFLP, as the two loci are super closely linked.
In another family, if the first germ cell where the FCD mutation occurred happened to carry the "1 band" morph, everyone that gets the FCD mutation will alos inherit the "1 band" morph.
IN SOME CASES, (RARE!) THE MUTATION THAT GIVES THE PHENOTYPE IS ALSO WHAT CAUSES THE PRESENCE/ABSENCE OF THE RFLP. IN SUCH CASES, YOU'LL BE WARNED ABOUT IT IN THE QUESTION.
Cheers,
Pam
(PS: keep up the good work!)
1) This question was posted on this very blog a few weeks ago (together with others). you'll find them under "archives"!
2) I-3 and I-4 a re from different families! The girl in generation III receives the "2 bands" morph from her mom, who does not have FCD, and who therefore cannot pass it on. So, the only chance for the girl to have FCD is by inheriting from her dad.Her dad passes on a "1 band" morph. If we look at his parents and siblings, we see that in his family, FCD comes with the "2 bands" morph, and since he passed on the "1 band", he did not pass on FCD to his daughter. So yes, III-1 WILL be able to cook!
3) For those who were not in 334 (or who forgot their population genetics), the fact that something is dominant does not mean it's not rare!!
If the frequency of the FCD (mutated) allele is 1% in a population, and this allele does not confer any advantage or disadvantage, this frequency is going to remain the same over time. In fact, one might argue that not being able to cook could decrease one's chances of finding a mate and generate an offspring, so the mutated, dominant FCD allele should in fact disappear from the population over time!
I hope this helps
Cheers
Pam
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