Single Gene disorders

Question 1

What is an electrogram

Answer 1

Plot of DNA sequencing results

Question 2

Define a substitution/missense disease

Answer 2

All cases of sickle cell anaemia causes by the same mutation in beta globulin gene

Question 3

Define nonsense mutaitons

Answer 3

Duchenne muscular dystrophy is often caused by nonsense mutations in dystrophin gene

Question 4

what clinical example is there of an Insertion mutations

Answer 4

Familiar hypercholesterolemia results in elevated levels of blood lipids. A genetic study was carried out on a large consanguineous pack family.

Question 5

Define delation mutation

Answer 5

Delation of phenylalanine residue at position 508

Question 6

What is autosomal dominant inheritance

Answer 6

Characteristic is manifested in the heterozygote of both sexes
Not linked to a sex chromosome
affected have 1/2 chance of passing it on.

Question 7

What is autosomal recessive inheritance

Answer 7

Characteristic is not manifested in the heterozygote of both sexes •Not linked to a sex chromosome

Affected individuals are born to unaffected parents

Question 8

What are the mutations responsible for recessive traits

Answer 8

Lack of gene expression
Lack of protein production
Production of a protein with reduced or absent function.

Question 9

Define X linked dominance

Answer 9

Characteristic is manifested in the heterozygote of both sexes •One parent is affected •There are significantly more affected females than males •Affected females are typically show milder characteristics (and more variable expression) than males

Question 10

Define X linked recessive

Answer 10

Characteristic is not manifested in the heterozygote of both sexes •Are mostly male•Affected males are born to unaffected parents•No male- to male inheritance

Question 11

What factors can effect the phenotype of single gene disorders.

Answer 11

Penetrance
Expressivity
Phenocopy
Enviroumntal effects

Question 12

What test can be carried out to view for mutations

Answer 12

Newborn screening 
carrier testing 
prenatal test
preimplantation genetic diagnosis 
predicative and presymptomatic testing.