Genetics

Question 1

Familial Hypercholestoremia

Answer 1

Autosomal dominant leading to LDL deficiency

Question 2

Huntington’s Disease

Answer 2

Autosomal dominant-triplet repeat disorder. Gain of function mutation.

Question 3

Myotonic Dystrophy

Answer 3

Autosomal Dominant. DMPK mutation, highly pleiotropic.

Question 4

Achondroplasia

Answer 4

Autosomal dominant. Deficient in FGFR3 (growth factor). Relatively normal life span.

Question 5

Marfan’s Syndrome

Answer 5

Mutation in Fibrillin-1 gene. Autosomal dominant. Pleiotropic. Dominant negative mutation.

Question 6

Osteogenesis Imperfecta

Answer 6

Autosomal dominant. Brittle bone syndrome.

Question 7

Neurofibromatosis

Answer 7

Autosomal Dominant. Mutation in NF-1 gene, NF-1 codes for nuerofibrillin which is a tumor suppressor gene. Has variable expressivity-some have cafe au lait spots and other have small tumors all over the body, and Lisch nodules in the eyes. Allelic heterogeneity.

Question 8

Acute Intermittent Porphyria

Answer 8

Autosomal dominant. Causes an enzyme deficiency, one of the only AD that do that.

Question 9

Cystic Fibrosis

Answer 9

Mutation in the CFTR gene.

Question 10

Sickle Cell Anemia

Answer 10

Autosomal Recessive

Question 11

Phenylketonuria (PKU)

Answer 11

Autosomal Recessive

Question 12

Tay Sachs Disease

Answer 12

Hexosaminidase A deficiency. Autosomal recessive.

Question 13

Congenital Deafness

Answer 13

Autosomal recessive

Question 14

Hemochromatosis

Answer 14

Build up of iron in the body. Autosomal recessive. Delayed age of onset. Allelic heterogeneity.

Question 15

Alkaptonuria

Answer 15

Delayed age of onset. Autosomal recessive.

Question 16

Homocystinuria

Answer 16

Autosomal recessive.

Question 17

Galactosemia

Answer 17

Autosomal recessive

Question 18

Alpha 1-antitrypsin deficiency

Answer 18

Autosomal recessive

Question 19

SCID due to adenosine deaminase deficiency

Answer 19

Autosomal recessive

Question 20

What is the molecular basis for most autosomal recessive disorders?

Answer 20

Loss of function mutations (e.g., enzyme deficiencies) is

Question 21

Pseudo-autosomal dominant disorder

Answer 21

An autosomal recessive condition that is present in two or more generations in the family, looking like its following a dominant inheritance pattern. Seen when there is a high carrier frequency (sickle cell) and high incidence of consanguinity

Question 22

X-linked recessive disorders (female)

Answer 22

Very rare in the population, color blindness is the only known one.

Question 23

X-linked recessive

Answer 23

More common in males, skipping generations is common, fathers give disease allele to carrier daughters who give to affected sons. No male to male transmission.

Question 24

Duchenne Muscular Dystrophy

Answer 24

Severe form, early on set, short life span. Low genetic fitness so men who have it don’t usually live long enough to pass it on. Muscle is replaced by adipose. Due to loss of the dystrophin protein. X-linked recessive.

Question 25

Becker Muscular Dystrophy

Answer 25

X-linked recessive. Milder form of DMD, not usually seen until after 25 years of age.

Question 26

Glucose-6-phosphate dehydrogenase deficiency

Answer 26

X-lined recessive. Hemolytic anemia upon ingestion of primaquine, sulfa drugs.

Question 27

Hemophilia A and B

Answer 27

Deficiency of clotting factor VIII resulting in increased bleeding after minor trauma. Most serve cases involve inversion of intron sequences. Allelic heterogeneity

Question 28

Lesch-Nyhan nSyndrome

Answer 28

HGPRT deficiency. Leads to hyperuricemia, gout, and self mutilation. X-linked recessive.

Question 29

Red-green color blindness

Answer 29

X-linked disease. Seen in males and females (more common in males).

Question 30

X-Linked SCID

Answer 30

Defect in SCIDX1 gene. X-linked recessive. Defect in gamma receptor which causes the T-cells to be unable to mature, leading to lack of Bcell function.

Question 31

X-linked Dominant

Answer 31

Skipping of generations is not common, more females than males, no male to male transmission,affected male gives disease to all his daughters. Variable expressivity due to X inactivation.

Question 32

Rhett Syndrome

Answer 32

Lethal in males. X linked dominant. Leads to hand wringing and shrinking head in females.

Question 33

Incontinentia Pigmenti

Answer 33

X linked dominant. Males dies, females get tastes and blisters that become marble cake appearance later on.

Question 34

Vitamin D Resistant Rickets

Answer 34

X linked dominant.

Question 35

Leber Hereditary Optic Neuropathy

Answer 35

Mitochondrial disease. Progressive blindness around 20-30 years.

Question 36

MELAS

Answer 36

Mitochondrial encephalopathy, lactic acidosis, and stroke like episodes

Question 37

MERRF

Answer 37

Myoclonic epilepsy with ragged red muscles fibers. Mitochondrial inheritance.

Question 38

The triplet repeat disorders

Answer 38

Huntingtons, myotonic dystrophy, and fragile X.

Question 39

Retinitis Pigmentosa

Answer 39

Digenic disorder. Leads to progressive visual impairment. Results in a mutation in two independent genetic loci.

Question 40

Imprinting

Answer 40

Certain gene is methylated which silences the gene, making the other one active. Some genes are only active when transmitted by the mother or father.

Question 41

Prader Willi

Answer 41

Caused by micro deletion on paternal chromosome or maternal uniparental Disomy. Absence of SNRPN.

Question 42

Angelman Syndrome

Answer 42

Deletion of maternal UBE3a gene or uniparental Disomy of SNRPN.

Question 43

Fragile X

Answer 43

Triplet repeat on X chromosome on the 5’ end of the FMR1 gene, resulting in methylation which silences the gene. Results in learning disabilities, elongated face, prominent ears, and macro orchidism. Shows anticipation and is worse when it comes from mom.

Question 44

Linked

Answer 44

Genes are said to be linked when they are arranged on the same chromosome, close enough that they have a recombination frequency of less than 50%