Biochem14

Question 1

List the autosomal recessive diseases.

Answer 1

Albinism
ARPKD
Cystic fibrosis
Glycogen storage diseases
Hemochromatosis
Mucopolysaccharides (Except Hunter's)
Phenylketonuria
Sickle cell anemias
Sphingolipidoses (Except Fabry's)
Thalassemias

Question 2

What is the gene/chromosome and common deletion in Cystic Fibrosis?

What does this cause cellularly?

Answer 2

CFTR gene on Chr 7
deletion of Phe 508

Abnormal protein folding –> degradation of channel before reaching cell surface

Question 3

What is the normal function of the CFTR channel?

Answer 3

Secretes Cl- in Lungs & GI tract

Reabsorbs Cl- from sweat

Question 4

Why are males steril in Cystic fibrosis?

Answer 4

Bilateral absence of vas Deferens

Question 5

The defective Cl- channel in CF leads to a what?

Answer 5

secretion of abnormally thick mucus that plugs the lungs, pancreas, and liver.

Recurrent pulmonary infections

Question 6

What type of bacteria cause the recurrent pulmonary infections in CF?

Answer 6

Pseudomonas & S. aureus

Question 7

Newborns with CF have what finding?

Answer 7

Meconium ileus

Question 8

T/F - Cystic fibrosis is the most common lethal genetic disease of the white population

Answer 8

True

Question 9

What is diagnostic for CF?

Answer 9

INcreased concentration of Cl- in sweat test

Question 10

What is the treatment for CF?

MOA?

Answer 10

N-acetylcysteine

Loosens mucous plugs by cleaving disulfide bonds within mucous glycoproteins

Question 11

What is the mnemonic for the X-linked Recessive disorders?

Answer 11

Be Wise, Fool’s GOLD Heeds Silly HOpe

B - Bruton's agammaglobulinemia
W - Wiskott-Aldrich syndrome
F - Fabry's disease
G - G6PD deficiency
O - Ocular albinism
L - Lesch-Nyan syndrome
D - Duchenne's (and Beckers) muscular dystrophy
H/S - Hunter's Syndrome
H - Hemophilia A and B
O - Ornithine transcarbamoylase deficiency

Question 12

Why do females have much less severe symptoms in X-linked recessive disorders?

Answer 12

Random X chromosome inactivation in each cell

Question 13

What type of mutation is seen in Duchenne’s muscular dystrophy?

Answer 13

X-linked FRAMESHIFT mutation –> deletion of dystrophin gene –> accelerated muscle breakdown

Question 14

Where does weakness begin in DMD?

Answer 14

Pelvic girdle muscles – moves superiorly

Question 15

What causes the pseudohypertrophy of calf muscles seen in DMD?

Answer 15

fibrofatty replacement of muscle

Question 16

What is a characteristic sign of a child with DMD?

Answer 16

Gower’s sign

assistance of upper extremities to stand up

Question 17

What is the onset of DMD?

Answer 17

Before age 5

Question 18

What is the function of Dystrophin?

Answer 18

Helps anchor muscle fibers (skeletal & cardiac)

Question 19

How do you diagnose DMD?

Answer 19

INcreased CPK & Muscle biopsy

Question 20

What is the onset of age in Becker’s muscular dystrophy?

Answer 20

Adolescence or early adulthood

Question 21

What does the X-linked defect in Fragile X syndrome cause?

Answer 21

Methylation and expression of the FMR1 gene

Question 22

What are the clinical findings in Fragile X syndrome?

Answer 22

Macroorchidism (big balls)
Long face w/ large jaw
large everted ears
Autism
Mitral valve prolapse

“Fragile X = eXtra large testes, jaw, ears”

Question 23

What is the 2nd most common genetic cause of mental retardation ?

Answer 23

Fragile X syndrome (1st - downs)

Question 24

What are the Trinucleotide repeat expansion diseases?

Answer 24

“TRY (trinucleotide) HUNTING for MY FRIED EGGS (X)”

Huntington’s Dz
Myotonic dystrophy
Friedreich’s ataxia
Fragile X syndrome

Question 25

What is the trinucleotide repeat in Fragile X syndrome?

Answer 25

CGG

Question 26

What is the trinucleotide repeat in Friedreich’s ataxia?

Answer 26

GAA

Question 27

What is the trinucleotide repeat in Huntington’s dz?

Answer 27

CAG

Question 28

What is the trinucleotide repeat in in Myotonic dystrophy?

Answer 28

CTG