Biochem For Real

Question 1

Missense Mutation

Answer 1

Substitution results in a changed amino acid

Ex: sickle cell disease (valine replaces glutamic acid)

Question 2

Silent mutation

Answer 2

Substitution codes for the same amino acid

Base change in 3rd codon position (tRNA wobble)

Question 3

Nucleotide excision repair

Answer 3

Endonucleases release oligonucleotides with damaged bases
Bulky distorting lesions
Ex: xeroderma pigmentosa

Question 4

Base excision repair

Answer 4

Glycosylase removes altered base and creates an AP site
Repair of spontaneous/toxic deamination
Occurs throughout cell cycle

Question 5

Mismatch repair

Answer 5

Newly synthesized strand is recognized and mismatched nucleotides are removed
G2 phase of cell cycle
Ex: deficient in Lynch (HNPCC) syndrome

Question 6

Nonhomologous end joining

Answer 6

Brings together 2 ends of DNA fragments to repair DS breaks

Ex: ataxia telangiectasia, Fanconi anemia

Question 7

I cell disease

Answer 7

Inherited lysosomal storage disorder
Defect in N-acetylglucosaminyl-1-phosphotransferase: failure of Golgi to phosphorylate mannose residues on glycoproteins

Coarse facial features, clouded cornea, restricted joint movement, high levels of lysosomal enzymes

Question 8

Vimentin

Answer 8

Mesenchymal tissue

Question 9

Desmin

Answer 9

Muscle

Question 10

Cytokeratin

Answer 10

Epithelial cells

Question 11

GFAP

Answer 11

Neuroglia

Question 12

Neurofilaments

Answer 12

Neurons

Question 13

Kartagener Syndrome

Answer 13

Immotile cilia due to dynein arm defect
Infertility 
Bronchiectasis 
Recurrent sinusitis
Situs Inversus (dextrocardia)

Question 14

Osteogenesis imperfecta

Answer 14

Autosomal dominant
Decreased production of Type I collagen (hydroxylation of prolines and lysine) 
Multiple fractures
BLUE SCLERAE
Hearing loss
Tooth abnormalities

Question 15

Ehlers-Danlos

Answer 15

Faulty collagen synthesis (problems with cross-linking collagen)
Hyperextensible skin, tendency to bleed, hypermobile joints
Berry aneurysm
Classical: type V collagen
Vascular: type III collagen

Question 16

Marfan Syndrome

Answer 16

Defect in fibrillin (forms a sheath around elastin)

Question 17

Emphysema

Answer 17

Alpha1 anti trypsin deficiency – excess elastase activity

Question 18

Southern blot
Northern blot
Western blot
Southwestern blot

Answer 18

Southern-DNA
Northern-RNA
Western-protein
Southwestern-DNA binding proteins

Question 19

Prader-Willi Syndrome

Answer 19

Maternal imprinting: loss of paternal allele; maternal allele is silent
Hyperphagia, obesity, intellectual disability, hypogonadism, hypotonia

Question 20

Angelman syndrome

Answer 20

Paternal imprinting: maternal deleted and paternal is silenced
“Happy puppet”
Seizures, inappropriate laughter, ataxia and severe MR

Question 21

Frame shift mutation

Answer 21

Deletion or insertion of nucleotides not divisible by 3
Protein may be shorter or longer
Function may be disrupted or altered
Ex: Duchenne’s and Tay Sachs