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    Evolution and Heredity

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    Part I:

    Imagine you have a friend who is getting married and plans on starting a family right away. She asks your advice about preconception genetic screening because she is concerned about the chance that her future children could have cystic fibrosis. Her fiancé has a sister that has cystic fibrosis, and she has a cousin who has the disease, although none of her siblings have it.

    Determine the probability of your friend being a carrier of the disease. One uncle and a cousin are marked as having the disease. (Along with the written determination, complete the pedigree of genotypes of friend's family members)

    What is the likelihood that if she married this person, her children would inherit cystic fibrosis? Would you suggest she (or any of her family members) undergo genetic testing before starting a family? Why or why not?

    Part II:

    Briefly describe how genetic knowledge assists us with testing for one specific genetic disorder other than cystic fibrosis. Describe the disorder, genetic tests currently in use, and any potential for gene therapy or possible treatments. Use an authoritative reference to support your points.

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    Solution Preview

    I hope that you will find the attached following useful, I have put at the bottom of the article pages that you can source for reference material, Please get back to me if you require further guidance as what I have set out to do is help you with this.

    Sorry I was having trouble attaching the file so I have put it here below, Unfortunately that loses the colour and the links. Sorry I had problems attaching, if there is aproblem you could email me directly or through Brainmass I will send you the file mick_rodway@hotmail.com

    The inheritance of cystic fibrosis follows Mendelian genetics i.e it is inherited as a monohybrid allele which means that you can have three possible genotypes.

    I have used the following terminology:

    CC: Homozygous Dominant (N.B. The phenotype of this individual is that they do not have the disease at all or are they a carrier of the disease)

    Cc: Heterozygous(N.B. The phenotype of this individual is that they do not have the disease at all but they are a carrier of the disease)

    cc: Homozygous Recessive (N.B. The phenotype of this individual is that they do have the disease)

    There are three possible ways that an individual could be born with the disease the first two are quite unlikely:

    1. Both parents were cc.
    2. One parent was Cc and the other parent had the disease.
    3. Both parents were carriers of the disease.

    The third description is the most likely and the children from this family would have the following probabilities:

    P=0.5 whether they are male or female.

    P=0.25 whether they are cc
    P=0.5 whether they are Cc
    P=0,25 whether they are CC.

    Look at the information given:

    The fact that an uncle has the disease but her parents do not must mean that her grandparents are:
    Cc and Cc.

    The fact that she has a cousin that also has the disease could mean one of two things:
    a. That the cousin is the uncle's child and that his partner is either Cc or cc. ( I think the pedigree indicates that this is not the case)
    b. That the cousin has parents who are both Cc.
    Because her grandparents were both Cc, consider the genotypes of your friend and her 3 siblings.

    From the information given we are told that none of her siblings have the disease, (she has three).

    Her mother or father, whoever has descended from the grandparents, I have numbered them number 3 has a 0.25 probability of being CC and a 0.5 probability of being Cc.

    Because we do not know the genetic history of the your friends other parent other than we know they do not have the disease. We will have to make some assumptions:

    Here are some scenarios:
    1. Tempting to think that as none of your friends siblings have the disease that they are neither carriers ...