Genetic Inheritance Session 23

Question 1

What are multifactorial traits ?

Answer 1

• Traits that are controlled by polygenes subject to environmental influences.

Question 2

What is a Pleiotropy ?

Answer 2

• A single mutant gene affects two or more distinct and seemingly unrelated traits

Question 3

What is penetrance used for ?

Answer 3

• it is used to describe whether or not there is a clinical expression of the genotype in the individual.
  For example: If a mutation in the gene responsible for a particular autosomal dominant disorder has 95% penetrance, then 95% of those with the mutation will develop the disease while the 5% will not

Question 4

Describe expressivity

Answer 4

• it describes the differences observed in the clinical phenotype between the two individual with the same genotype.

Question 5

What is the most common test to determine color blindness ?

Answer 5

• Ishira test

Question 6

What are examples of X-linked recessive disorders ?

Answer 6

• Color blindness
• Duchenne muscular dystrophy
• Hemophilia

Question 7

What is Duchenne muscular dystrophy and what is it caused by ?

Answer 7

• It is the degeneration of the muscles, individuals pass away by 20-25 years old.
• Caused by the absence of a protein called dystrophin, which causes calcium to leak into the cell which stimulates an enzyme that dissolves muscle fibres

Question 8

What are the different types of Hemophilia and how do you treat it ?

Answer 8

• Hemophilia A : absence of clotting factor VIII
• Hemophilia B : absence of clotting factor IX
• Hemorrhages can be stopped with transfusions of fresh blood or the missing clotting protein

Question 9

What is an example of X linked dominant disorder ?

Answer 9

• Fragile X syndrome