7. Wha 9. Marfan syndrome is an inherited condition that affects the connective tissue, resulting in
unusually long bones and spinal curvature, as well as vision, cardiac, and respiratory
problems. The syndrome tends to become increasingly severe over time. The following
pedigree shows inheritance of Marfan syndrome in a multigenerational famil (5)y.
8. Wh
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9. Tra
Th
the
III
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a) How is this syndrome inherited (dominant, recessive or sex-linked)?
2
b) Can you determine individual 114's genotype? Explain.
b.
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c) Individual III and I12 are considering having another child. What is the probability that
this child will have Marfan syndrome? Explain using a Punnett square.

The correct answers are :

a) syndrome Could be autosomal recessive or dominant

b) If it is autosomal recessive - no ,

and if it is autosomal dominant - yes, (II-4) - Aa

c) probability of the another child :

Autosomal recessive: Aa x aa 50%

Autosomal dominant: aa x Aa 50%

Explanation:

a) Marfan syndrome could be inherited by the autosomal recessive or dominant pattern on the basis of following characters according the pedigree gives:

- transmitted by anyone regardless of sex male or female

- characters should not skip generations

- A cross between affected person and an normal person should produce approximately half of the affected offspring.

b) Assuming that autosomal dominant than there is two possibilities :

1) in case of I 2 genotype is heterozygous which means it is Aa which will produce Aa Aa aa and aa with crossing with aa as per pedigree however it is incorrect according the offspring given in II.

2) If I 2 is AA- then offspring will be Aa, Aa, Aa and Aa. which is correct according the pedigree.

thus, the answer is - Aa

c) the punnet square as per question is :

              II2  -  Aa ×  II1 - aa

      A      a

a    Aa     aa

a    Aa     aa

similar with autosomal recessive

thus, the correct answer is 2 out of 4 that is 50%