Young: Medical Genetics - Extended Matching Questions

Table of Contents

1. Chapter 4
   1. Question 1
   2. Question 2

Question 1

Instructions: Each group of extended matching questions consists of lettered options followed by a list of numbered problems/questions. For each numbered problem/question select the one lettered option that is most closely answers the question. You can use the lettered options once, more than once, or not at all.

Theme: Mendelian inheritance

Options:

1. Autosomal dominant
2. Autosomal recessive
3. X-linked dominant
4. X-linked recessive
5. Mitochondrial
6. Y-linked
7. Pseudoautosomal

In the families below at least one member has a genetic disorder. Select the most appropriate mode of inheritance from the available options.

1

Scenario 1   A mother, who has two brothers with unexplained mental retardation, is concerned that her son is showing delay in achieving many of his developmental milestones. She recalls that her mother also had a brother with severe learning difficulties. Choose... Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive Mitochondrial Y-linked Pseudoautosomal This 3 generation history of affected males related through the female line is typical of X-linked recessive inheritance. See Page 77.Incorrect. See Page 77.Your answer has been saved.

2

Scenario 2   A mother who has a brother and sister with severe visual loss is concerned that this could have implications for her own children. There is no other family history of visual problems. On drawing up the family tree it emerges that the mother's parents were first cousins. Choose... Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive Mitochondrial Y-linked Pseudoautosomal The parental consanguinity and the presence of affected brother and sister in a single sibship point strongly to autosomal recessive inheritance. See Page 74.Incorrect. See Page 74.Your answer has been saved.

3

Scenario 3   A man who inherited muscle weakness from his mother has noticed that his son is starting to show similar features. This is subsequently confirmed by muscle biopsy. Choose... Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive Mitochondrial Y-linked Pseudoautosomal A three generation history with an example of male to male transmission is typical of autosomal dominant inheritance. See Page 71.Incorrect. See Page 71.Your answer has been saved.

4

Scenario 4   A woman with muscle weakness states that one of her sisters and both of her brothers are similarly affected. This seems to have been inherited from her mother's side of the family. Review of the family tree confirms that many maternal relatives have been affected, but surprisingly none of the affected males has ever transmitted the condition to any of his children or grandchildren. Choose... Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive Mitochondrial Y-linked Pseudoautosomal This could be autosomal dominant inheritance, but it is surprising that no males have transmitted the disorder to either sons or daughters. Mitochondrial inheritance is characterised by exclusive maternal transmission as no sperm mitochondria survive in the fertilised ovum. See Page 86.Incorrect. See Page 86.Your answer has been saved.

5

Scenario 5   A genetic study carried out on a small isolated island identifies a many individuals with a new form of adult onset tremor. Many generations have been affected. A detailed analysis of the family pedigrees reveals that the parents of all affected adults have been at least distantly related. Choose... Autosomal dominant Autosomal recessive X-linked dominant X-linked recessive Mitochondrial Y-linked Pseudoautosomal This could be autosomal dominant inheritance, but in a small isolated community descended from a small number of common ancestors, pseudoautosomal inheritance is more likely. See Page 81.Incorrect. See Page 81.Your answer has been saved.