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Homework Help: 3 Genetics/Genomics Questions

  1. Oct 12, 2008 #1
    I am new to this site, so if I make a mistake with the format, I apologize.


    **Question #1**:
    1. The problem statement, all variables and given/known data

    1. You are trying to make a 100-nucleotide long chain of DNA using a DNA synthesizer machine. What must be the minimum efficiency of each coupling (nucleotide addition) step, so that the full-length product chain is at least 25% of all the DNA chains synthesized (i.e., failure sequences must not be >75% of the total)?

    2. Relevant equations and the attempt at a solution

    I thoroughly understand the mechanism by which the DNA synthesizer machine works, but am not sure how to calculate efficiency. No further information was given in the question, and the only information I could find on google/in my notes was just explaining how the machine works. Any help/thoughts would be greatly appreciated.


    **Question #2**:
    1. The problem statement, all variables and given/known data

    How would you replace a mouse gene by the wild type copy of a human gene?

    2. Relevant equations and the attempt at a solution

    I know that the answer is using the Cre-loxP system. I don't, however, know the exact steps to doing a translocation using this method. I found multiple sites that give the steps for a deletion, but none that went into any detail about a translocation.


    **Question #3**:
    1. The problem statement, all variables and given/known data

    A cDNA library is made with mRNA isolated from liver tissue. When a cloned cDNA from the library is digested with restriction enzymes EcoRI (E), HindIII (H), and BamHI (B), the restriction map shown in Fig. (a) is obtained. When this cDNA is used to screen a cDNA library made with mRNA from brain tissue, 3 identical cDNAs with the restriction map shown in Fig. (b) are obtained. When either cDNA is used to synthesize a uniformly labeled radioactive probe and the probe is allowed to hybridize to a Southern blot prepared from genomic DNA digested singly with the enzymes EcoRI, HindIII or BamHI, an autoradiogram shown in Fig. (c) is obtained. When either of these cDNA-derived radioactive probes is used to hybridize to a Northern blot prepared with poly (A)+ RNA isolated from liver and brain tissues, the pattern of bands in Fig. (d) is seen. Fully analyze these data and then answer the questions below

    a. Do the cDNAs derive from the same gene?
    b. Why do the cDNAs have different restriction maps?
    c. Why are different sized bands seen in the Northern blot?
    d. Why do some of the bands seen on the whole genome Southern blot have different sizes than some of the restriction fragments in the cDNAs?

    The figures for this question can be found at: http://photos-g.ak.facebook.com/photos-ak-sf2p/v360/61/45/8826787/n8826787_42325350_4285.jpg [Broken]

    2. Relevant equations and the attempt at a solution

    I have a guess for each of the four answers, but ultimately that's all it is: a guess. If anyone would be willing to either confirm/correct any of the guesses, that'd be greatly appreciated.

    a. yes
    b. alternative splicing
    c. due to an intron
    d. the restriction map may not contain the whole gene


    Thank you!
    Last edited by a moderator: May 3, 2017
  2. jcsd
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