Help with Mendel logic...!

[CRANC]

I have an in class topic on the D. Melanogaster fly. we're breeding them and doing test corsses etc.

I have to answer this lat question on logic. Logic isn't my strong suit.

 

Below are three of Mendel's premises and a conclusion.

 

Does the conclusion follow logically from the three premises stated? Explain your answer. if it does not then provide an alteration to addition to the premises that would lead to that conclusion.

 

The three premises as follows:

 

1. parents do not transmit traits directly but do so through genes, which code for the traits.

2. Not all copies of genes are identical, and different alleles exist coding for different expressions of each trait.

3. each trait is governed by two alleles (gene versions) in each individual, one derived from each parent.

 

Conclusion: The offspring from the parental fly cross, conducted in week 2, will either show parental traits completely or not at all. they will not show traits blended from both parents.

 

So, there it is. any help would be appreciated. I'm new, so don't hold it against me!

[Mokele]

There's no way to know without knowing the genotypes of both parent flies and the nature of the dominance interaction of the allele in question.

[Paralith]

Well, whether or not they show traits blended from both parents depends on the nature of the dominance interaction between the different alleles, as Mokele said, but I don't think you need to know the genotypes of the parents - I think the "conclusion" is just not worded clearly. It probably should read, "The offspring from the parental fly cross, conducted in week 2, will either show their mother's version of the trait or their father's version of the trait. They will not show a version of the trait that is a blend of both parents' versions." Of course if both parents have the same allele then the offspring would be exactly the same no matter what. (Barring any environmental effects.) But it seems to me this problem is assuming they are different.

 

If the mother's and father's alleles for the trait in question have a simple Mendelian dominant/recessive relationship, then the conclusion is correct. If they have a codominant relationship, then the conclusion is incorrect. (This is assuming, of course, that we're talking about ONE gene for ONE trait that has at least 2 different alleles.)

[CRANC]

There's no way to know without knowing the genotypes of both parent flies and the nature of the dominance interaction of the allele in question.

 

I re read the question and we're not given the genotypes of the parent fly's, unfortunately. its just a logic based question where we make the best assumptions we can from the info we're given!

shit, hey

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oh, and all the Q wants to know is does the badly worded conclusion follow the 3 hypothesis given my mendel? if so, in what way, if not, in what way.

Paralith, ty for your reply mate

[jolan]

i know that i must sound really really stupid still, but if we were to hand it in as an assignment question, what would the answer actually be?? *hint hint*

[Paralith]

If I actually got this as an assignment I would ask the teacher about it because based on what I know I need more information before I can actually answer it. And I've already stated what info I would need and what the answer would be depending on that info.

[jolan]

okie dokie, will go get some help right now

thanks for all the help

[Gabrielle B]

Well at least I know I'm not the only one who was confused by that q:eek:.....I just rambled about ratios and added an extra premises:

"that a trait may not show up in an individual but can still be passed on to the next generation" that refers to heterozygous genes (Xx) if you didnt know that

 

 

 

http://anthro.palomar.edu/mendel/mendel_1.htm