The Inheritance of Human Disease

Question 1

What are some features of Mendelian Inheritance?

Answer 1

Autosomal dominant, autosomal recessive, X-linked (mitochondrial) = multifactorial inheritance. NOTE THERE IS SMALL ENVIRONMENTAL CONTRIBUTION

Question 2

What are some features of non Mendelian Inheritance?

Answer 2

Methylation/ Imprinting, Mitochondrial inheritance, mosaicism = multifactorial inheritance

Question 3

What is an autosomal recessive mutation?

Answer 3

2 faulty copies of the gene are required to cause disease. Often only one generation is affected, with a 1/4 risk of an affected child with carrier parents. There is an increased likelihood in consanguineous families (families who have the same common ancestor)

Question 4

What are some X-linked recessive genes?

Answer 4

Dystrophin, haemophilia, SHOP1 and MT1 - x chromosomes carry lots of genes

Question 5

Who can pass on x-linked diseases?

Answer 5

Only the mother if it’s a son but the mother and father to a girl

Question 6

How is a female carrier affected by x-linked diseases?

Answer 6

Carries the mutation but does not show major features of the disease

Question 7

What causes only one x chromosome to be active in females?

Answer 7

Random x inactivation - with disease half of the cells will have a working gene

Question 8

What are Single Nucleotide Polymorphisms?

Answer 8

Alterations in DNA sequence that occur every 100 to 300 base pairs - not all are disease causing as each ‘normal’ person has on avg 3 million

Question 9

What are Copy Number Variations?

Answer 9

Extra or missing stretched of DNA

Question 10

Common disease vs common variants of Mendelian and common disorders

Answer 10

Mendelian - high penetrance but rarer

Common - low penetrance but common