Molecular and Genetics Practice Question

Question

The accompanying pedigree most likely represents which inheritance pattern?

Question images

Family pedigree for the inheritance question.

100%

Answer Choices

Autosomal dominant
Autosomal recessive
Mitochondrial
X-linked recessive
X-linked dominant

Show Answer and Explanations

Autosomal dominant — Correct answer

Correct. The trait is not passed from unaffected individuals. It is passed from males and females to half the offspring. Two people can be affected and have unaffected children.

Autosomal recessive

Incorrect. When two people are affected by an autosomal recessive condition, all of their children usually inherit the condition.

Mitochondrial

Incorrect. Mitochondrial inheritance should result in females passing the trait to all offspring. Males will not pass the condition.

X-linked recessive

Incorrect. X-linked recessive conditions passed from females will affect all her sons, and none of her daughters. The daughters will be carriers. If the father has the condition but the mother does not, none of the sons will be affected (they receive the Y chromosome), and the daughters will all be carriers. If the mother and father have the condition, all children will be affected.

X-linked dominant

Incorrect. X-linked dominant conditions passed from females will affect half of her sons and half of her daughters. Nobody will be an unaffected carrier. X-linked dominant conditions in affected males will not be passed to his sons, and will be passed to all of his daughters.

Summary

Summary: In AD inheritance the trait is not passed from unaffected individuals. It is passed from males and females to half the offspring. Two people can be affected and have unaffected children.