Genetics

Question 1

What are the features of a pedigree with an autosomal dominant condition?

Answer 1

1) In every generation; 2) limited to ‘one side’ of the family

Question 2

What are the features of a pedigree with an autosomal recessive condition?

Answer 2

1) Not present in every generation; 2) more likely in the presence of consanguineous relationships

Question 3

How many autosomal recessive alleles does a person carry?

Answer 3

2-5

Question 4

What % of mutations are tested for in CF?

Answer 4

85%

Question 5

Why might a recessive condition be common?

Answer 5

1) Because heterozygosity may confer survival benefit; 2) can be caused by multiple different types of mutations

Question 6

What is the risk of a live infant being born with a major congenital abnormality in the population?

Answer 6

0.5-1%

Question 7

What are the signs an X-linked condition has been inherited from a mother?

Answer 7

1) The condition is present in her brothers; 2) She displays the ‘1/2 phenotype’ - e.g. in DMD, her CK was greater than that of the general population

Question 8

How may a person have an X-linked condition should they not have inherited it?

Answer 8

De novo mutation