Information from the case studies he wanted us to read

Question 1

The name of one molecular/cellular diagnostic test for Down Syndrome

Answer 1

QF-PCR and FISH

Question 2

The name of the abnormal cellular process that can cause the chromosomal defect in patients

Answer 2

Non-disjunction in meiosis (remember nondisjunction in meiosis I always causes two copies of the chromosome in a single gamete -> trisomy 21)

Question 3

Gene name and domain inside the gene that is commonly affected by mutations (Marfan syndrome)

Answer 3

fibrillin-1; Amino acid substitutions in the cbEGF domains that disrupt calcium binding

Question 4

The major structures/tissues in the body that are commonly affected by the mutation in fibrillin-1

Answer 4

wall of the aorta, rings and leaflets of heart valves, periosteum, and ciliary zonule of the eye

Question 5

Type I diabetes

What is insulin, where is it produced, and how is it released into the body?

Answer 5

Insulin is a hormone made by beta cells of the pancreas and is released into the blood when blood glucose increases

Question 6

Signal transduction and regulation of glycogen synthesis and degradation in liver

Answer 6

Insulin induces glycogen synthesis, glucagon=degradation

Question 7

Insulin vs glucagon?

Answer 7

Glucagon made by alpha cells of pancreas

C-peptide is marker of insulin synthesis (endogenous)

Question 8

C-peptide- marker or bioactive molecule?

Answer 8

C-peptide is marker of insulin synthesis (endogenous)

Question 9

MLPA- what is it?

Answer 9

Multiplex ligation dependent probe amplification (diagnosis of DMD)

Question 10

DMD inheritance

Answer 10

X-linked inheritance

Question 11

Dystrophin-cell function and molecules it connects?

Answer 11

Dystrophin binds actin and skeletal muscle

Question 12

Non structural roles of dystrophin in muscle

Answer 12

Low dystrophin can allows excess Ca2+ to enter sarcolemma which allows water to enter mitochondria causing lysis. Mitochondria defect causes increase in stress induced calcium levels and ROS.

Question 13

Why hereditary spherocytosis is caused (and associated protein disruption)

Answer 13

Normal shape disrupted due to defects in genes of ankyrin, spectrin

Question 14

Integral membrane proteins of RBC plasma membrane—functions?

Answer 14

Glycophorin- rich in sialic acid=hydrophilic

Band 3-anion exchanger: Cl- for HCO3

Question 15

X-ALD

1. Protein disrupted?
   a. Location-how does it get there?
   b. Cellular activity

Answer 15

1. ALD =peroxisomal membrane transport protein (ATP-Binding cassette protein class D=ABCD protein).
   ABCD- specific for Long chain fatty acid synthase?
   A. Peroxisome-
   C-terminal sequence=SKL binds PTS1R
   PTS1R:SKL complex binds Pex14p (receptor on peroxisomal membrane) that transports protein into peroxisome.
   Transport fatty acid into peroxisome

Question 16

Remember two disease examples that are caused by triplet repeats expansion.

Answer 16

Huntington Disease= CAG repeat > 40 repeat=Huntington

Fragile X Syndrome= CGG repeats

Question 17

Remember the name of two lab methods that can be used to genetically diagnose triplet repeats expansion.

Answer 17

PCR and southern blot

Question 18

I-Cell Disease

Biochemical defect-result of defect

Answer 18

GlcNac (N-acetylglucosamine) Phosphotrasferase defect (transfers phosphate to mannose residues so they can go to golgi) = cells don’t go to golgi, but are secreted due to “default” pathwayaccumulate as inclusions

Question 19

3. Fibroblasts from i-cell disease
   a. What can they uptake and why?
   b. Therapeutic strategies and limitations?

Answer 19

a. Lysosomes can uptake enzymes made extracellularly because plasma membrane has M6P receptors (via receptor mediated endocytosis)
b. Strategy- replace defective enzyme with normal one
**phosphotransferase insertion into cys gogli
**treatment with lysosomal enzymes
Limitations: enzymes would have to be put in all the cells, continuous injections, and lysosomal enzymes would need to be stabilized until they were put into the lysosome (so you don’t get digested)

Question 20

I-Cell Disease

2. M6P modification—pre or post translational?
   a. Location
   b. Enzymes
   c. Mechanism
3. Fibroblasts from i-cell disease
   a. What can they uptake and why?
   b. Therapeutic strategies and limitations?

Answer 20

2. POST-translational!!!
   a. Cis-golgi network
   b. GlcNAc phosphotransferase
   GlcNAc phosphodiesterase
   c. In RER, Man8(GlcNAc)2 is made and sent to cis-golgi.
   In cis golgi, glcNAc phosphotransferase adds phosphate to C-6 of mannose.
   glcNAC phosphodiesterase removes the glcnac part = M6P