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Genetics Problem

  1. Feb 14, 2006 #1
    Hi Everyone,

    I have been trying to solve these problems with no success. Please help. Thanks in advance.

    1. Determine the nature of the traits being studied (ie. whether linked or sex-linked). Explain how you reached the conclusion.

    Attempted Answer:

    The cross was between 5 mutant males (wym) and 5 wild type females (WYM) and another cross was between 5 wild type males (WYM) and 5 mutant females (wym).

    The results achieved in the first cross was 43 wild type males, 35 wild type females, 2 females WyM and 1 female Wym.

    The results achieved in the second cross was 15 male wym, 5 male WYM, 20 female WYM and 1 female Wym.

    I concluded that these traits were linked on ym and YM becaues they appear together in both generations. I also concluded that they were not sex-linked traits because they were present in both generations of the male and female.

    2. Show all the progenies you may obtain in the cross between 5 triple-mutant males (wym) and five triple-heterozygous females (WYM) (consider the recombination event)

    Attempted Answer:

    male wym X female WYM
    wYm, wYm, wyM, Wym, WYm, WYm... I'm not sure that this is right.


    Once again I thank you in advance for your help.
     
  2. jcsd
  3. Feb 15, 2006 #2

    iansmith

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    If you are going to state that YM are linked you may have to explain this (unless it is a typo)

    You may want to reviewed the sex-link traits in your note. The presence of all trait is not identicative of the absence of sex-link. You have to pay close attention to the female trait and what the male gets and vice and versa. Specifically look at the difference between cross 1 and cross. What is the difference?

    You are repeating yourself (look at the bolded type and the one before). There's a possibility of 8 different combinations without taking answer one in consideration.
     
    Last edited: Feb 15, 2006
  4. Feb 15, 2006 #3
    I assumed that they were linked because of the fact that they appeared in 2 successive generations together. Is it correct to state that ym are linked?

    In the first cross it seems that the wild type is present more often in both males and females and the mutant type is not present as often. Also there were no male mutants present. It seems in this case that the mutations are not sex-linked since it would only require one mutant gene on the x chromosome to indicate that there is a sex-linkage. Is there still chance of any linkage?

    In the second cross it seems that male mutations are more common and the female wild type is more common. Thus is is alternating from the previous generation. I think that this is indicative of linkage but I am not sure if this is indicative of sex-linkage. It seems as though it is.



    Do the 8 different combinations also take the recombination into consideration? Also, are the ones that I entered on the right path or are they incorrect? (wYm, wyM, Wym, WYm)

    Thank you for your continued help.
     
  5. Feb 15, 2006 #4

    iansmith

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    When 2 traits are linked you will always get both trait together. It's very unlikely that you will get a recombination event that seperate both traits. So if it was linked, all the offspring would either have YM or ym but no yM or Ym.

    You are on the right tract.

    I highligthed the important comment. In sex linkages when the female is homozygous, the males will always have the traits of the mother but none of the traits of their father. So what are the traits absent in the male offspring but present in the parent males.


    There is 8 combination that are possible (WYM, WYm, Wym, WyM, wYM, wYm, wyM and wym) if the individuals are heterozygous for all the traits and if none of the traits are linked. The answer will also take a different direction depending on your answer in question number one.
     
    Last edited: Feb 15, 2006
  6. Feb 15, 2006 #5

    iansmith

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    For the last question remember that you have to do a punnet square.
     
  7. Feb 19, 2006 #6
    I have re-read some of the concepts and attempted to answer the questions again.

    The first cross between five mutant males (wym) and five wild type females (WYM) resulted in 43 wild type males (WYM), 35 wild type females (WYM), 2 wYM females and 1 wyM female.

    I concluded that the genes are linked in this case because in most cases with the rare recombinance the genes appear in the parental forms. Also, the frequency at which the parental form appears is greater than 50% and the recombinance is very rare.

    I also concluded that the genes are X-Linked because there were no mutant males in the F1 generation thereby showing that the gene is likely X-Linked. An F2 generation cross would help in proving this as it is expected that the mutation will reappear in the F2 generation.



    The second cross was between five wild type males (WYM) and five mutant females (wym). This resulted in 15 mutant males (wym), 5 wild type males (WYM), 20 wild type females (WYM) and 1 Wym female.


    I concluded that the genes are linked here as well because once again it is very rare for a recombinance event to take place and thus the parental form of the gene is more often seen.

    I also concluded that the genes are not X-Linked because of the appearance of the wild type male in the F1 generation. Can you please double check this as I am not sure if this is correct? In fruit flies it is known that the W, Y and M are X-Linked but in this circumstance it does not appear that it is. (W = red eyes, Y = golden-brown body, M = expanded wings; w = white eyes, y = yellow body, m = miniature wings)



    All the progenies that can be obtained from a cross between 5 triple-mutant males and five triple-heterozygous females will be as follows (this also includes the recombinance event):

    WYM, WYm, Wym, WyM, wYM, wYm, wyM and wym

    How would you set up the Punnett-Square with 3 traits?

    Thank you for the continued help.
     
  8. Feb 19, 2006 #7

    iansmith

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    That seems to be correct

    As far as I know this is also correct because if there was a X-linked phenotype I would expect only mutant male and wild type female.
     
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