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Biology: Genetics: Hardy-weinberg + restriction enzyme

  1. Nov 5, 2011 #1
    Hi, everyone, I was hoping if you can clear up some confusion for me.
    I have the questions and book answer to these hw problem. The hard part for me is understanding WHY these answer turn out to be the way it is.

    1: Hardy-weinberg:

    1. The problem statement, all variables and given/known data

    14.4 Consider a population that, for unknown reasons, is not in Hardy-Weingberg equilibrium for some gene.
    (a) can you calculate the genotype frequencies if you know the allele frequencies?
    (b) can you calculate the allele frequencies if you know the genotype frequencies?
    Answer:
    (A) No.
    (B) Yes.

    2. Relevant equations

    So.. why is does it come out like this? Can you explain to me why these two answer are correct?

    3. The attempt at a solution

    Because, I thought if H-W doesn’t applied, you cannot calculate either of this answer..right?

    ------
    Question 2:
    1: Genetic Cloning/restriction enzyme

    1. The problem statement, all variables and given/known data

    10.13: A haploid genome size of about 100 Mb. If this genome is digested with NotI (an eight-baed cutter), approximately how many DNA fragments would be produced? Assume equal and random frequencies of the four nucleotides.

    Answer: 4^(8) = 65,526
    So, every 65,526 based, the enzyme makes a cut. Thus, 100,000,000 bp / 65,526 bp = 1527 fragments.

    2. Relevant equations

    so, why did you take the 4^8? how do you know to put "4" and put it to the 8th power? where is this formula even coming from?

    3. The attempt at a solution

    I, actually, have no idea..

    Because, I thought if H-W doesn’t applied, you cannot calculate either of this answer..right?

    --------
    Question 3:

    1. The problem statement, all variables and given/known data

    10.6: You decide to clone your pet dog, which is brown with black spots. You take a few somatic cells from your dog and perform a somatic cell nuclear transfer procedure using an egg from a female dog that is black. In this procedure, the egg nucleus is removed and replaced with that from a somatic cell. What color fur will the puppy clone of your dog have?
    Answer: brown with black spot.

    2. Relevant equations

    so, why does the book answer come out to be this way? Also, is the oocyte a fertilized or unfertilized egg, right? Since, this procedure could only work with an unfertilized egg?

    3. The attempt at a solution

    So.. my logic behind is this... So, is it b/c you have replaced the inner nucleus of the oocyte and replaced it with a somatic cell; thus, in turn, the oocyte will only expressed the somatic cell genotype ..which lead to the phenotype of brown with black spots. .. .
    --------

    Thank ahead,
     
  2. jcsd
  3. Nov 5, 2011 #2

    Ygggdrasil

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    Science Advisor

    The genotype frequencies will always tell you the allele frequencies. For example, if you have 20 individuals who are AA, 10 individuals who are Aa, and 5 individuals who are aa, it's easy to count the number of A alleles (20*2 + 10) and the number of a alleles (10+ 5*2), and calculate the allele frequencies.

    Here's a related problem that might get you thinking in the correct direction: If you throw a six-sided dice four times in a row, what is the probability of rolling a 1, then a 2, then a 3 then a 4?

    You basically have the correct answer. The dog's traits are encoded in its DNA. Removing the nucleus from the oocyte remove's the oocyte's original DNA, including any DNA that would cause the dog to have black hair. Therefore, because the clone contains only DNA from your pet dog, its physical characteristics (at least those dependent on genes) will come from only your pet dog and not from the egg donor dog.

    An oocyte is an unfertilized egg. I think somatic cell nuclear transfer only works with unfertilized eggs although I am not 100% sure that this is true.
     
  4. Nov 5, 2011 #3

    Can you explain further why can't you do the opposite by "calculate the genotype frequencies if you know the allele frequencies"?
     
  5. Nov 5, 2011 #4

    Ygggdrasil

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    Science Advisor

    Well, let's say you have 10 A alleles and 10 a alleles. You can put these alleles together in many different ways to get different combinations of genotypes. For example, you could put them together as 5 AA individuals and 5 aa individuals. Or you could put them together as 5 Aa individuals. Or you could have 1 AA individual, 3 Aa individuals, and 1 aa individual. etc.

    Because there are many different ways of combining the alleles to get different genotypes, you cannot determine genotype frequencies from allele frequencies.
     
  6. Nov 6, 2011 #5

    Thank you SO MUCH! I LOVE YOU! :D
     
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