Flashcards in Biochemistry - First Aid Deck (609)
DNA exists in the...
condensed, chromatin form in order to fit into the nucleus.
Negatively charged DNA loops...
twice around positively charged histone octamer to form a nucleosome "bead".
Histones are rich in...
the amino acids lysine and arginine.
H1 binds to the...
nucleosome and to linker DNA, thereby stabilizing the chromatin fiber.
In mitosis, DNA will...
condense to form chromosomes.
DNA and histone synthesis occurs during...
The only histone that is not in the DNA core is...
condensed, transcriptionally inactive, sterically inaccessibl.e.
less condensed, transcriptionally active and sterically accessible.
In DNA replications, the template strand cytosine and adenine are...
methylated which allows mismatch repair enzymes to distinguish between old and new strands in prokaryotes.
DNA methylation at CpG islands acts to...
Histone methylation usually...
represses DNA transcription.
Histone acetylation acts to...
relax DNA coiling, allowing for transcription.
Adenine and Guanine; 2 rings
Cytosine and Thymine; 1 ring
(thymine has a methyl)
Deamination of cytosine makes...
uracil. Uracil is found in RNA; thymine in DNA.
The G-C bond has...
3 H bonds and is stronger than the A-T bond which has 2. Increased G-C content leads to increased melting temp of DNA.
Amino acids necessary for purine synthesis
base + deoxyribose
base + deoxyribose + phoshpate
(linked by 3'5' phosphodiester bond)
Purines de novo synthesis
start with sugar + phosphate (PRPP); add base
Pyrimidine de novo synthesis
make temporary base (orotic acid); add sugar and phosphate; modify base
Ribonucleotides are synthesized...
first and are converted to deoxyribonucleotides by ribonucleotide reductase.
Carbamoyl phosphate is involved in 2 metabolic pathways:
de novo pyrimidine synthesis and the urea cycle.
Various antineoplastic and antibiotic drugs function by interfering with nucleotide synthesis:
2. Mycophenolate and Ribavirin
6. Methotrexate, trimethoprim and pyrimethamine
inhibits dihydroorotate dehydrogenase
Mycophenolate and Ribavirin inhibit...
6-MP and its prodrug Azathioprine inhibit...
de novo purine synthesis.