Week 3: Genetic Conditions

Question 1

De novo mutations are most common in which type of inheritance

Answer 1

Autosomal dominant

Question 2

What is the inheritance of cystic fibrosis

Answer 2

Autosomal recessive

Question 3

What is cosanguinity

Answer 3

Relationship between second cousins or closer

Question 4

Genetic testing is not currently done in children under what age

Answer 4

18yo

Question 5

Clinical features of DiGeorge syndrome (22q11.2)

Answer 5

CATCH 22

• Cardiac
• Abnormal facial features
• Thymic aplasia
• Cleft palate
• Hypo-PTH, Hypo-calcaemia (due to aplasia of parathyroid gland)

Question 6

Why do pts with DiGeorge syndrome (22q11.2) tend to get autoimmune disease

Answer 6

Thymus gland not developed, so cannot regulate self tolerance

Question 7

Definition of anticipation in genetic dz

Answer 7

Disease becomes more severe/ has earlier onset in each subsequent generation

Question 8

Definition of incomplete penetrance in genetic dz

Answer 8

Not everyone with the genotype will express the phenotype

Question 9

Definition of genetic heterogeneity in genetic dz

Answer 9

A number of different genes can cause the same phenotype

eg long QT syndrome

Question 10

Definition of variable expressivity in genetic dz

Answer 10

Many different phenotypes from the same genotype

Question 11

Definition of imprinting in genetic dz

Answer 11

Phenotype depends on which parent the gene was inherited from

eg Angelman, Prader-Willi

Question 12

Definition of mosaicism in genetic dz

Answer 12

Multiple cells with different genotypes in 1 individual (due to mitotic errors)

Question 13

Give the names of the following trisomies:
13
18
21

Answer 13

13: Patau’s
18: Edward’s
21: Down’s

Question 14

Give the name of the following sex chromosome aneuploidies:
X0
XXX
XXY

Answer 14

X0: Turner’s syndrome

XXX: Klinefelter’s syndrome

XXY: Triple X syndrome

Question 15

Which aneuploidies are associated with low IQ

Answer 15

• All the trisomies (21, 18, 13)

- Triple X syndrome

Question 16

Heart complications associated with Down’s syndrome

Answer 16

1. AVSD/ VSD
2. Tetralogy of fallot
3. PDA

Question 17

Down’s syndrome is associated with increased risk of which cancers

Answer 17

• Testicular cancer
• ALL
• AML

Question 18

Heart complications associated with Patau’s syndrome

Answer 18

1. VSD

2. PDA

Question 19

Heart complications associated with Turner’s syndrome

Answer 19

1. Bicuspid aortic valve
2. Aortic valve stenosis
3. Coarctation of aorta

Question 20

Which of the following are increased/ decreased in Down’s screening:

beta-hCG
AFP
PAPP-A
Inhibin A
Estriol
Nuchal translucency

Answer 20

DECREASED

• AFP
• PAPP-A
• Estriol

INCREASED

• Nuchal translucuency
• beta HCG
• Inhibin A

Question 21

Components of Down’s syndrome triple and quadruple test

Answer 21

Triple test

1. betaHCG
2. AFP
3. Estriol

Quadruple test
above +
4. Inhibin A

Question 22

Difference between incomplete penetrance & variable expressivity

Answer 22

Incomplete penetrance: gene may or may not be expressed. Same phenotype if gene is expressed

Variable expressivity: gene will be expressed but not all the features appear in the phenotype