Biochemistry

Question 1

Histone amino acids

Answer 1

Lysine & arginine. Helps in positive charge to bind negatively charged DNA

Question 2

Significance of orotic acid

Answer 2

De novo purine and pyrimidine synthesis pathways

Question 3

Degenerate nature of genetic code

Answer 3

Degenerate/redundant means that multiple codons code for each amino acid

Question 4

Semiconservative nature of DNA replication defined

Answer 4

Means that daughter DNA molecules have one old and one new strand. Conservative would keep two original strands together and create two new strands double-helixed to themselves

Question 5

Exonuclease activity in prokaryotic DNA replication

Answer 5

Prokaryotes!! DNA polymerase III has 3’ - 5’ exonuclease (DNA replication proofreading)
DNA polymerase I has 5’-3’ exonuclease for removing RNA primer

Question 6

Lac operon simplified

Answer 6

CAP (catabolite activator protein) region, promoter region, and operator region. Operator region is blocked by repressor protein until

Question 7

MOA of chain termination in nucleotide analogs?

Answer 7

3’ modification which prevents addition of next nucleotide. Note that the analog will be incorporated but the nucleotide AFTER the analog cannot be incorporated

Question 8

Anti-smith antibodies diagnostic for what disease? Target protein function

Answer 8

Specific in diagnosis of lupus. Antibodies to small nuclear ribonucleoproteins (snRNPs) important in forming spliceosome for mRNA processing

Question 9

Structure of tRNA molecule from 3’ to 5’ end

Answer 9

3’ end ends with CCA which is site of attachment of appropriate amino acid. T-arm is next which is recognized by ribosome. D-arm is closest to 5’ end and is recognized by aminoacyl-tRNA synthetase (adds correct amino acid)

Question 10

N-acetylglucosaminyl-1-phosphotransferase enzyme defect causes what?

Answer 10

I-cell disease. Failure of phosphorylation of mannose residues on proteins in the Golgi which usually dictates trafficking to lysosomes. When defective, lysosome enzymes are exocytosed instead

Question 11

Vesicle trafficking proteins: COPI, COPII, and clathrin

Answer 11

COPI -> retrograde transport in the golgi (trans to cis) or from cis golgi to ER (still retrograde)
COPII -> anterograde transport
Clathrin -> transport from golgi to lysosomes or cell membrane

Question 12

Granulation tissue composed of what kind of collagen

Answer 12

Type III: as are blood vessels, uterus, and fetal tissue

Question 13

Type II collagen found in what structures

Answer 13

Cartilage, nucleus pulposus, vitreous body