Biochemistry Review II: Genetics

Question 1

This messed up mnemonic is going to help you (maybe) remember which disorders are autosomal recessive:

Answer 1

Fabry's tale (Fabry's disease):
Duke, the muscular (Duchenne's muscular dystrophy)
Hunter (Hunter's syndrome)
Brutally (Bruton's agammaglobulinemia)
Lysed (Lesch-Nyhann)
the Albino (ocular albinism)
Gopher (G6P deficiency)
w/o being 
aWare (Wiskott-Aldrich)
it was a
Fragile (Fragile X)
Hemophiliac (Hemophilia A & B)

Question 2

Duchenne’s muscular dystrophy manifests in early life (usually before age 5) with pseudohypertrophy of the calf muscles, cardiomyopathy; kids will classically use Gower’s maneuver to get up.
What gene is deleted in this disorder?
How do you diagnose it?
How is it inherited?
What is the difference between Duchenne’s muscular dystrophy and Becker’s?

Answer 2

Duchenne’s = Deleted Dystrophin gene. Dystrophin is an anchor for skeletal and cardiac muscle fibers.
Diagnosis is by muscle biopsy and high serum CPK.
This is X-linked recessive.
Becker’s is a mutated dystrophin, it’s more common, less severe, and shows up later.

Question 3

This syndrome is the second most common cause of genetic mental retardation after Down syndrome:
Which gene is implicated?
What are the clinical findings?

Answer 3

Fragile X
FMR1 gene (think “Fragile Mental Retardation”)
Clinically, you see Xtra large testes, ears, and mitral valve (causes mitral valve prolapse). Kids are sometimes autistic.

Question 4

The three most common trisomies:

Answer 4

Trisomy 21 = Down
Trisomy 18 = Edwards’
Trisomy 13 = Patau’s

Question 5

Cri-du-chat syndrome is associated with VSD. What chromosomal abnormality is implicated?

Answer 5

Microdeletion, short arm of 5.

46,XX or 46,XY, 5p-

Question 6

You remember Williams syndrome as being associated with elfin facies and extreme friendliness, but there are other clinical features you might be asked about.
What chromosome is the one with the problem in Williams?

Answer 6

Williams = microdeletion on 7.

These children are very vitamin D sensitive (can cause hypercalcemia), have heart problems. Elastin is also deleted.