Modes of inheritance

Question 1

Mode of inheritance of sickle cell anaemia

Answer 1

Autosomal recessive

• defective globin genes
• when exposed to hypoxia/acidaemia → sickling of RBCs → painful crisis

Question 2

Mode of inheritance of cystic fibrosis

Answer 2

Autosomal recessive

Question 3

Mode of inheritance of congenital adrenal hyperplasia

Answer 3

Autosomal Recessive

Question 4

Mode of inheritance of oculocutaneous albinism

Answer 4

Autosomal recessive

Question 5

Mode of inheritance of thalassemia

Answer 5

Autosomal recessive

Question 6

Mode of inheritance of Tay-Sachs disease

Answer 6

Autosomal recessive

• destruction of the nerve cells in the brain and spinal cord
• commonly becomes apparent when a baby is 3-6 months and loses ability to turn over, sit, crawl etc
• other: seizures, hearing loss, inability to move
• enzymatic defect (beta hexosaminidase A) →toxic build up of GM2 gangloside → destruction of nerve cells
• death often occurs in early childhood

Question 7

Mode of inheritance of galactosaemia

Answer 7

Autosomal Recessive

Question 8

Mode of inheritance of Prader-Willi

Answer 8

Uniparental disomy

(deletion mutation)

• ‘imprinting’ → gene required for normal function comes from only one parent
• if this gene is delated or both genes come from the other parent (uniparental disomy) → syndrome will occur
• in Prader-Willi only parental copy of the gene is active (chromosome 15) → therefore either a parental gene is deleted or both copies come from mum

Features:

• hypotonic and difficult to feed as infants
• learning disability and obesity later on in life

Question 9

Mode of inheritance of Angelman’s syndrome

Answer 9

Uniparental disomy

• ‘imprinting’ → gene required for normal function comes from only one parent
• if this gene is delated or both genes come from the other parent (uniparental disomy) → syndrome will occur

Features:

• happy temper
• little speech
• severe learning disability
• poor attention spam
• epilepsy

Question 10

Mode of inheritance of Marfan’s syndrome

Answer 10

Autosomal dominant

Features of Marfan’s syndrome:

• tall statute
• high arched palate
• mitral valve disease
• lens dislocation
• joint laxity
• arachnodactyly

Question 11

Mode of inheritance of achondrodysplasia

Answer 11

Autosomal dominant

• achondrodysplasia = dwarfism
• abnormal conversion of cartilage into bone → epiphyseal growth of long bones is retarded

Question 12

Mode of inheritance of Huntington’s disease

Answer 12

Autosomal Dominant

Question 13

Mode of inheritance of neurofibromatosis

Answer 13

Autosomal dominant

Question 14

Mode of inheritance of Noonan’s syndrome

Answer 14

Autosomal dominant

normal development of various parts of the body is prevented →ususual characteristics:

• abnormal facial features
• heart defects
• short stature
• developmental delay
• bleeding problems
• bone malformations
  *

Question 15

Mode of inheritance of tuberous sclerosis

Answer 15

Autosomal dominant

• benign tumours develop across the body: brain, skin, kidney, heart, eyes and lungs
• seizures, learning disability, developmental delay
• skin abnormalities, kidneys abnormalities, lung disease

Question 16

Mode of inheritance of Duchenne muscular dystrophy

Answer 16

X-linked recessive

• 30% of causes → due to new mutation

Question 17

Mode of inheritance of colour blindness

Answer 17

X -linked recessive

Question 18

Mode of inheritance of Fragile X syndrome

Answer 18

X - linked recessive

Question 19

Mode of inheritance of Haemophilia A and B

Answer 19

X-linked recessive

Question 20

Mode of inheritance of glucose-6-phosphate dehydrogenase deficiency

Answer 20

X-linked recessive

Question 21

Mode of inheritance of William’s syndrome

Answer 21

Autosomal dominant (deletion mutation)

• microdeletion of chromosomal material at 7q11
• features: short stature, elf-like face, hypercalcaemia as infant, supravalvular aortic stenosis, mild-moderate learning disabilities

Question 22

Mode of inheritance of Cri-Du-Chat

Answer 22

Autosomal dominant (delation mutation)

Question 23

Mode of inheritance of Di-George syndrome

Answer 23

Autosomal dominant (deletion mutation)

Question 24

Mode of inheritance of Vitamin D - resistant Rickets

Answer 24

X-linked dominant

Question 25

Mode of inheritance of Leber Hereditary Optic Neuropathy

Answer 25

Mitochondrial

• inherited from the mother

Question 26

Familiar hyperchlesterolaemia - mode of inheritance

Answer 26

Autosomal dominant

• mutation in a gene coding for LDL receptor