Etiology of Disease

Question 1

Velo-cardio-facial syndrome

Answer 1

Deletion of long arm of chromosome 22 at q11

Question 2

G6PD Deficiency

Answer 2

X-linked recessive mutation on the long arm in the G6PD gene

Question 3

Hemochromatosis

Answer 3

Autosomal recessive condition with allelic heterogeneity in HFE genes

Question 4

Neurofibromatosis Type I

Answer 4

Autosomal dominant condition with allelic heterogeneity in NF1 gene for neurofibromin

Question 4

Fanconi’s anemia

Answer 4

Autosomal recessive inheritance of 1 of 13 genes belonging to the FANC family repair complex

Question 4

Angelman Syndrome

Answer 4

The loss of the mother’s contribution of the Angelman gene via deletion or by paternal unidisomy or by inappropriate imprinting of mother’s copy or by activated silencers in mother’s copy

Question 6

Patau Syndrome

Answer 6

Aneuploidy of Chromosome 13 (47 +21) -80% nondisjunction; 20% mosaicism

Question 7

Tuberous Sclerosis

Answer 7

Autosomal dominant condition with locus and allelic heterogeneity in TSC1 or TSC2 genes (hamartin and tuberin)

Question 7

Vitamin D Resistant Rickets

Answer 7

X-linked dominant mutation in PHEX gene

Question 8

Achondroplasia

Answer 8

Autosomal dominant condition with NO locus or allelic heterogeneity in FGFR3 gene [other mutations cause completely different phenotypes!]

Question 8

Cystic Fibrosis

Answer 8

Autosomal recessive with high allelic heterogeneity of CFTR gene on chromosome 7

Question 9

Alpha thalassemia

Answer 9

Autosomal recessive inheritance of between 1 and 3 copies of a mutated thalassemia gene on chromosome 16

Question 10

Edwards Syndrome

Answer 10

Aneuploidy of Chromosome 18 (47+21) -80% nondisjunction; 20% mosaicism

Question 12

Williams syndrome

Answer 12

Deletion of long arm of chromosome 7 at q11 (elastin gene lost!)

Question 13

Duchenne’s Muscular Dystrophy

Answer 13

X-linked recessive mutation in the dystrophin gene of the long arm

Question 14

Wolf-Hirschhorn Syndrome

Answer 14

Partial deletion of Chromosome 4 in p15 and p16 area

Question 14

Inconscientia Pigmenti

Answer 14

X-linked dominant mutation of exons from the IBKBG gene

Question 15

Prader-Willi Syndrome

Answer 15

Either: the loss of the father’s contribution of the Prader-Willi gene via deletion or by maternal unidisomy

Question 16

Retts Syndrome

Answer 16

X-linked dominant mutation in MECP2, a methyl-CpG binding protein

Question 17

MELAS

Answer 17

Point mutation in mitochondrial tRNA

Question 19

Cri-du-chat Syndrome

Answer 19

Partial deletion of chromosome 5 in p15

Question 20

Kleinfelter Syndrome

Answer 20

Aneuploidy of X chromosome in a male (47 XY +X) -2/3 Maternal Nondisjunction -1/3 Kleinfelter variances (e.g. 48 XXXY)

Question 21

Leber Hereditary Optic Neuropathy

Answer 21

Mitochondrial missense mutation in Complex I

Question 23

Marfan’s syndrome

Answer 23

Autosomal dominant condition with allelic heterogeneity in fibrillin gene

Question 24

Hydrops fetalis

Answer 24

Autosomal recessive inheritance of 4 copies of mutated thalassemia gene on chromosome 16

Question 25

OTC Deficiency

Answer 25

X-linked recessive mutation in the long arm

Question 26

Turner Syndrome

Answer 26

Aneuploidy of X chromosome (45 X) -2/3 Paternal Nondisjunction -1/3 Mosaic of 46 XX/45 X or 46 XY/45X

Question 27

Down Syndrome

Answer 27

Aneuploidy of Chromosome 21 (47 +21) -94% from maternal non-disjunction

Question 29

Huntington’s Chorea

Answer 29

Autosomal dominant condition as a result of anticipated expansion of trinucleotide repeats in the Huntingtin gene 10% de novo

Question 30

Myotonic Dystrophy

Answer 30

Autosomal dominant condition due to repeats of a CTG in the 3’ region of the DMPK gene with variable age of onset