Autosomal Recessive Inheritance

Question 1

Double heterozygote

Answer 1

An individual who has two different gene mutations at two separate genetic loci (unaffected)

Question 2

Sickle cell disease

Answer 2

Abnormalities in the structure of hemoglobin

Question 3

Molecular genetics of Sickle Cell Disease

Answer 3

Point mutation

Glu6Lys

Question 4

Clinical features of sickle cell

Answer 4

Anemia
Painful abdominal and bone crises
Infarcts of internal organs and joints
Predisposed to infections/fevers

Question 5

Thalassemia

Answer 5

Abnormalities in the amount of hemoglobin resulting from an inbalance in the relative amount of alpha and beta chains

Question 6

3 methods for screening for hemoglobinopathies

Answer 6

1. MCV
2. Serum ferritin studies
3. Hb electrophoresis

Question 7

Tay sachs disease

Answer 7

Deficiency of Hex A enzyme causes the accumulation of GM2 ganglioside in lysosomes causing damage to neurons

Question 8

Clinical features of tay sachs

Answer 8

Onset around 6 months 
Loss of motor skills
Exaggerated startle reaction
Seizures, vision/hearing loss, intellectual disability, paralysis
Cherry red spot
Die in early childhood

Question 9

Cystic fibrosis

Answer 9

Insufficient transport of electrolytes across epithelial cells resulting in secretions that are thick and viscous

Question 10

Clinical features of cystic fibrosis

Answer 10

Chronic lung infection
Airway obstruction/destruction
Persistent coughing/wheezing/shortness of breath
Pancreatic insufficiency and malabsorption
Greasy, bulky stools
Salty sweat
Male infertility

Question 11

Molecular genetics of cystic fibrosis

Answer 11

Point mutations or small deletions in CFTR gene

Question 12

Clinical features of ataxia telamgiectasia

Answer 12

Ataxia or clumsiness in childhood
Mental decline
Occulocutaneous telangiectases
Immunodeficiency

Question 13

Molecular genetics of ataxia telangiectasia

Answer 13

Mutation in ATM gene on chromosome 11

Question 14

Clinical features of Friedreich ataxia

Answer 14

Progressive ataxia before 25
Foot deformities
Absent/ diminished tendon reflexes
Axonal sensory neuropathy
Dysarthria, weakness, scoliosis, incoordination of eye movements

Question 15

Molecular genetics of friedreich ataxia

Answer 15

Expansion of trinucleotide repeats in FXN gene

1-2% due to point mutations

Question 16

Compound Heterozygote

Answer 16

An individual who has two different abnormal alleles at a particular locus (affected)