Molecular biochem Flashcards
AA necessary for purine synthesis
glycine
aspartate
glutamine
term: most AA are coded by multiple codons
Degenerate/redundant
what AA are only coded by one codon
methionine (AUG)
tryptophan (UGG)
term: each condone specifies only 1 AA
unambiguous
term: read from a fixed starting point as a continuous sequence of bases
comma less
nonoverlapping
exceptions: some viruses
In both prokaryotes and eukaryotes, DNA replication is
semiconservative
both continuous and discontinuous (Okazaki fragments)
5’ to 3’ direction
Bloom syndrome (BLM gene mutation)
helicase deficiency
cannot unwind DNA template at replication fork
Makes RNA primer so DNA polymerase III can initiate replication
Primase
Prevents strands from reannealing
single-stranded binding proteins
DNA polymerases that prokaryotes only have
Polymerase I and III
Create single or double stranded break in helix to add or remove supercoils
DNA topoisomerase
Irinotecan/topotecan MOA
(eukaryote) inhibit topoisomerase I
etoposide/teniposide MOA
(eukaryote) inhibit topoisomerase II
fluoroquinolone MOA
(prokaryotes) inhibit TOP II (DNA gyrase) and TOP IV
- Elongates leading strand by adding deoxynucleotides to 3’ end
- Elongates lagging strand until reaches primer of preceding fragment
DNA polymerase III
prokaryotes only
DNA polymerase III synthesizes in what direction
5’ to 3’
DNA polymerase III proofreads in what direction
3’ to 5’ exonuclease
Drugs blocking DNA replication often have
modified 3’ OH that prevents addition of next nucleotide = chain termination
affects DNA polymerase III
Degrades RNA primer and replaces w/DNA
DNA polymerase I
prokaryotes only
same functions as DNA polymerase III
excises RNA primer w/ 5’ to 3’ exonuclease
T or F: All prokaryotic DNA polymerases can proofread using 3’ to 5’ exonuclease activity
True
Reverse transcriptase (RNA dependent DNA polymerase) that adds DNA (TTAGGG) to 3’ end of chromosomes to avoid loss of genetic material w/every duplication
telomerase
eukaryotes only
what is often dysregulated in cancer cells, allowing unlimited replication
telomerase
RNA processing that happens in the nucleus
capping of 5’ end w/7-methylguanosine cap
polyadenylation of 3’ end
splicing out introns
mRNA quality control occurs at
cytoplasmic processing bodies (P-bodies)
P-bodies contain
exonucleases
decapping enzymes
microRNAs
mRNA may be degraded or stored in P-bodies for future translation
fMet in prokaryotes stimulates
neutrophils chemotaxis
transcription and translation occurs in (gene expression)
G1, S, G2
never in M
Chemodrugs that affect S phase
5-FU (inhibits thymidylate synthase)
MTX (inhibits DHF reductase)
Chemodrugs that affect G2 phase
Bleomycin
Hodgkin lymphoma
causes pulmonary fibrosis
Chemodrugs that affect S phase
Paclitaxel
Vincristine
Vinblastine
Chemodrugs that are non-cell cycle dependent
cyclophosphamide
cisplatin
(blocks cycle nonspecifically)
DNA replication occurs during
S phase
Lynch syndrome (hereditary nonpolyposis colorectal cancer) has defect in what kind of DNA repair
Mismatch repair (single strand) S phase
Dry skin, extreme light sensitivity, skin cancer has defect in what kind of DNA repair
nucleotide excision repair (single strand)
G1 phase
DNA repair important for spontaneous/toxic deamination
Base excision repair (single strand)
throughout cell cycle
Ataxia-telangiectasia has defect in what kind of DNA repair
Nonhomolgous end joining (double strand)
Brings 2 ends of DNA fragments to repair double strand breaks
- no homology requirement
- some DNA may be lost
Nonhomologous end joining (double strand)
Requires two homologous DNA duplexes
- strand from damaged dsDNA repaired using complementary strand from intact homologous dsDNA as template
- restores duplexes accurately without loss of nucleotides
Homologous recombination (double strand)
Breast/ovarian cancer w/BRCA1 mutation and Fanconi anemia have defect in what kind of DNA repair
Homologous recombination (double strand)
alpha-amanitin found in Amanita phalloides death cap mushrooms inhibits
RNA polymerase II = no mRNA
severe hepatotoxicity
Actinomycin D or dactinomycin inhibits
RNA polymerase in both prokaryotes and eukaryotes
variants in splicing occurs in oncogenesis and many genetic disorders
beta thalessemia
Gaucher disease
Tay-sachs disease
Marfan syndrome
microRNAs are
- small non-coding RNA
- post transcriptionally regulate gene expression
- targets 3’ untranslated region of specific mRNA for degradation or translational repression
Part of tRNA necessary for tRNA ribosome binding
T-arm
Part of tRNA that has dihydrouridine residues necessary for tRNA recognition by correct aminoacyl tRNA synthetase
D-arm
