Lecture 21 - X-Linked Disorders and Mitochondrial Inheritance

Question 1

Examples of X linked recessive disorders?

Answer 1

Haemophilia, colour blindness, muscular dystrophy, fragile X syndrome

Question 2

Strategies for pedigree analysis?

Answer 2

examine family tree, provide probabilities

Question 3

Why don’t females produce twice as much X chromosome encoded genes?

Answer 3

lyonisation - random inactivation of one X chromosome in somatic cells (Barr Body)

Question 4

Phenotypic Analysis?

Answer 4

checking levels of clotting factors in family tree will determine degree of effect

Question 5

Problems with phenotypic analysis?

Answer 5

within-individual variation of normal clotting factors, requires fetal blood for diagnosis therefore late and difficult

Question 6

Methods of DNA analysis?

Answer 6

Polymorphic linkage, direct mutation detection

Question 7

Linkage analysis - RFLPs?

Answer 7

restriction fragment length polymorphisms

Question 8

Linkage analysis - VNTRs?

Answer 8

variable number tandem repeats

Question 9

Problems with linkage analysis?

Answer 9

requirement for family studies, non-paternity, recombination, lack of informative marker

Question 10

Options for carrier mother?

Answer 10

CV biopsy or amniocentesis, pre-implantation diagnosis (pick females, pick those w normal factor VIII gene)

Question 11

mt mutations?

Answer 11

maternally inherited, mainly effects high energy (due to ATP respiration effect) required organs e.g. brain and heart