QuestionGiven a pedigree with unaffected parents and one affected son and daughter, determine if myopia is dominant or recessive and list possible genotypes.
Studdy Solution
STEP 1
Assumptions1. The mother and father are unaffected but are carriers of the myopia gene.
. One son is unaffected, one son is affected, and one daughter is affected.
3. The affected son and daughter inherited the trait from their parents.
4. The parents are heterozygous with respect to this trait, meaning they have one dominant healthy allele and one recessive myopia allele.
STEP 2
First, we need to determine whether myopia is a dominant or recessive trait. In this case, both parents are unaffected but are carriers of the myopia gene. This means they have one dominant allele (healthy) and one recessive allele (myopia). If myopia was a dominant trait, the parents would be affected because they carry the allele. However, they are unaffected, which means myopia must be a recessive trait.
STEP 3
Next, we can list the genotypes of as many individuals represented by the pedigree as possible.The parents are heterozygous, meaning they have one dominant allele (healthy) and one recessive allele (myopia). We denote the dominant allele as 'A' and the recessive allele as 'a'. Therefore, the genotype of the parents is 'Aa'.
STEP 4
The unaffected son must have received the dominant allele from both parents because he is unaffected. Therefore, his genotype is 'AA'.
STEP 5
The affected son and daughter must have received the recessive allele from both parents because they are affected. Therefore, their genotype is 'aa'.
In conclusion, myopia is a recessive trait and the genotypes of the individuals in the pedigree are as follows- Parents Aa- Unaffected son AA- Affected son and daughter aa
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