For each of the following 1) indicate the genotypes of the parents, 2) provide a

Question

For each of the following 1) indicate the genotypes of the parents, 2) provide a Punnett Square depicting the particular example and list 3) phenotypic and 4) genotypic ratios of the possible outcomes.

Aicardi Syndrome is a relatively newly described X-linked disorder in which the corpus collosum does not develop in the brain. Other problems include disorders of the eye, seizures and profound cognitive development. Nearly all cases occur in females (although a few cases of XXY nature have been identified). Note that this is a syndrome and the true identification of the cause of the disease is yet to be determined. Assuming it is X-linked dominant, demonstrate a theoretical cross between a woman with the condition and a normal man.

Explanation / Answer

Aicardi syndrome is x-linked dominant disorder as it occurs in only females (XX/XXy)

1) indicate the genotypes of the parents:

affected female with genotype xAxA / xAxa

normal male xay

2) provide a Punnett Square depicting the particular example

If it is a heterozygous dominant female:

The F1 phenotype shows: 50% population effected.25% females and 25% males effected.

The F1 genotype shows:

xAxa   .........25%

xaxa    .........25%     

xAy   .........25%    

xay.........25%    

If it is a homozygous dominant female:

The F1 phenotype shows: 100% population effected. 50% females and 50% males effected. Males are more severely affected than females and its lethal in males.

The F1 genotype shows:

xAxa   .........50%

xAy   .........50%    

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