DNA replication Flashcards
Pyrimidine
Cytosine
Uracil
Thymine
Purine
Adenine
Guanine
Base + sugar (via glycosidic bond)
Nucleoside
Base + Sugar + Phosphate
Nuclotides
- Nucleic acid synthesis: DNA/RNA
- Energy currency of cell (ATP)
- Second messengers in cellular communication (G-protein)
- Ingredients of co-enzymes
- Regulators of metabolic reactions
Functions of nucleotides
Using ribose-1-p-lase to remove phosphate → Xanine oxidase to remove oxidase to become
Uric acid
AMP removes phosphate → adenosine will remove nitrogens using adenosine deaminase → _______
Becomes inosine
AMP removes phosphate → adenosine will remove nitrogens using adenosine deaminase → Becomes Inosine → Using ribose-1-p-lase to remove phosphate → Xanine oxidase to remove oxidase →
Becomes Uric Acid
___ _____: HGPRT enzyme will convert hypoxanthine back into inosine → Adenosine → AMP
To inhibit
Xanthine Oxidase deficiency
Hypouricemia
HGPRTase, PRPP deficiency
Hyperuricemia - Lesch-Nyhan syndrome/Juvenille Gout
Adenosine Deaminase deficiency
SCID
Over expression (SCID)
Hemolytic Anemia
Do NOT require large energy
Pyrimidine Synthesis
Need Carbon, nitrogen, and amino acids
Pyrimidine Synthesis
Cytosine deaminated to ______
uracil
Uracil degraded to
b-alanine
Folate and B12 required
Thymidylate synthesis (dTMP)
Thymidylate synthase
B-12
Inhibitors in cancer therapy
Involved in one carbon metabolism
Thymidylate synthesis
Precursor to thymidylate synthesis
dUMP
B12 used in what two forms in the body
Methylcobalamin
5-deoxyadenosyl cobalamin
DHFR inhibitor
Thymidylate synthase inhibitor
Chemotherapeutic agents
5-fluorouracil
Pyrimidine analog
Prevent one carbon metabolism
DHFR
Methotrexate & aminopterin
DHFR inhibitors
Nucleobases linked by 3’ to 5’ phosphodiester bonds
Chain growth is always 5’ to 3’
Primary structure of DNA synthesis
Double stranded; anti-parallel; twists into helix
Bases base paired through hydrogen bonding (Watson-Crick bond)
Secondary Structure
Adenine to thymine (uracil)
double bond
Cytosine to Guanine
Triple bond
3’ to 5” ________ Linkage of polynucleotides
Phosphodiester
A, t, G, or C - Nitrogenous base
Rungs of the ladder
Phosphate and Sugar backbone
Legs of ladder
Bidirectional
Synthesis is semiconservative
Characteristics of DNA strand synthesis
Both strands synthesized simultaneously
Strands unwind and separate (helicase, gyrase)
RNA primer required
Strands must be rewound
Synthesis is semiconservative
5’ to 3’ so one strand is continuous (Leading strand), other strand is discontinuous (Lagging strand)
Bidirectional
Pol I
Pol II
Pol III
3 prokaryotic polymerases for DNA synthesis
replication and repair
Pol I
implicated and repair
Pol II
main processing replicative enzyme (de novo synthesis of DNA) → To make it longer
Pol III
unwraps and separates strands (phosphodiester bonds)
Topoisomerase
breaks the base pairing (hydrogen bonds)
Helicase
binds to ssDNA
SSB
lays RNA primer (gives 3’-OH)
Primase
synthesizes DNA
DNA polymerase III
cuts out primers and re-synthesizes DNA
Polymerase I
reseals strand nicks after Polymerase I (Okazaki fragments)
Ligase
(type II topoisomerase) rewraps and recoils
Gyrase
inhibit DNA gyrase
Quinolones
Methotrexate, aminopterin, and trimethiprin
inhibit dihydrofolate reductase
Methotrexate
AZT-DNA chain terminator (no 3’ OH)
5’ fluorouracil- inhibits thymidylate synthesis
Chemotherapeutic agents
genetically active type of chromatin
Euchromatin
______ makes up chromosomes
Chromatin
Repetitive nucleotide sequences – called _____
telomeres
Quiescent/senescent
Go
Interphase
G1
S
G2