Biochemistry

Question 1

Lesch-Nyhan syndrome

Answer 1

defective purine salvage due to absent HGPRT

• leads to excess uric acid production and de novo purine synthesis
• treat with allopurinol or febuxostat
• HGPRT: Hyperuricemia, Gout, Pissed off (aggression, self-mutilation), Retardation, dysTonia

Question 2

transition vs. transversion mutation

Answer 2

• transition = purine to purine or pyrimidine to pyrimidine

- transversion = switch between types

Question 3

xeroderma pigmentosum

Answer 3

defective nucleotide excision repair
- specific endonucleases are not able to release damaged bases (ex: thymine dimers formed by UV radiation) so that DNA polymerase and ligase can repair

Question 4

HNPCC defect

Answer 4

mismatch repair

Question 5

ataxia telangiectasia defect

Answer 5

nonhomologous end joining

- unable to repair double-stranded DNA breaks

Question 6

mRNA start codon

Answer 6

AUG - methionine

Question 7

mRNA stop codons

Answer 7

UGA, UAA, UAG

- u go away, u are away, u are gone

Question 8

direction of DNA/RNA/protein synthesis

Answer 8

5’ to 3’ and N terminus to C terminus

Question 9

Kartagener Syndrome

Answer 9

primary ciliary dyskinesia

• immotile cilia due to dynein arm defect
• results in female and male infertility (increased risk of ectopic)
• can cause bronchiectasis, recurrent sinusitis, and situs inversus

Question 10

Collagen types and the tissues they are found in

Answer 10

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• bone, skin, tendon - type I
• Cartilage - type II
• Reticulin (skin) - type III
• Basement membrane - type IV

Question 11

Type I Collagen

Answer 11

most common - found in bone, skin, tendon, dentin, fascia, cornea, late wound repair

• Type 1 - bONE
• decreased production in osteogenesis imperfecta type 1

Question 12

Type II Collagen

Answer 12

cartilage (including hyaline), vitreous body, nucleus pulposus
- type 2 - carTWOlage

Question 13

Type III Collagen

Answer 13

Reticulin - skin, blood vessels, uterus, fetal tissue, granulation tissue

• vascular type of Ehler’s Danlos
• type 3 - threE D

Question 14

Type IV Collagen

Answer 14

Basement membrane, basal lamina, lens

• type IV under the floor (basement membrane)
• defective in Alport syndrome, targeted by Abs in Goodpasture

Question 15

osteogenesis imperfecta

Answer 15

genetic brittle bone disease

• most common is AD decrease in type 1 collagen formation
• mult fractures with minimal trauma, blue sclera, hearing loss, dental imperfections

Question 16

Ehlers-Danlos sydrome

Answer 16

faulty collagen synthesis – hyperextensible skin, tendency to bleed, and hypermobile joints

• 6+ types
• inheritance/severity varies, AR or AD
• may be associated with joint dislocation, berry and aortic aneurysms, organ rupture
• hypermobility type (most common)
• classical type (type V mutation)
• vascular type (type III collagen)