Tips: In autosomal dominant conditions, every afflicted individual has, at least

Question

Tips:

In autosomal dominant conditions, every afflicted individual has, at least, one parent with the affliction.

In autosomal recessive conditions, it is possible for afflicted individuals to sometimes have two parents that are both “normal” in phenotype, which would mean both parents are only carriers.

In X-linked recessive conditions, all, or most, afflicted individuals are male. Females of afflicted sons are carriers, and have “normal” phenotypes.

Problem: Pedigree 1

Which set of genetic disorders below follow the inheritance basis traced in this pedigree?

Achondroplasia, Familial hypercholesterolemia, Huntington's disease, Marfan syndrome

Albinism, Cystic fibrosis, Phenylketonuria (PKU), Tay-Sachs disease

Duchenne muscular dystrophy, Fragile X syndrome, Hemophilia A, Red-green colorblindness

Explanation / Answer

Autosomal recessive inheritance.

If it is X-linked recessive, the father of III-2 female must be affected (but, not affected).

If it is autosomal dominant, any of her parents must be affected (but, not affected).

It is an autosomal recessive condition because both of her parents are carriers, so she inherited each defective gene from their parents.

Diseases that follow autosomal recessive inheritance pattern are, familial hypercholesterolemia, Cystic fibrosis, albinism, Phenylketonuria (PKU), Tay-Sachs disease, Duchenne muscular dystrophy.

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