BMSC 220 - Topic 5

tasnimjaisee's version from 2017-09-26 16:59

Section 1

Question Answer
DNA replication is semi-Conservative Each daughter cell will contain old dna and one strand of new dna
DNA has a high degree offidelity ensuring
DNA polymerasesmultisubunit enzymes that catalyze the synthesis of DNA
DNA replicationMore complex than a single enzymatic reaction; numerous proteins and specific DNA sequences are also involved; came froms tudies in eukaryotes
All polymerases synthesize DNA in which direction?5 to 3 direction; (therefore, read DNA template in the 3 to 5 direction)
DNA polymerases can add a new deoxyribonucleotide only to a?preformed primer strand (3’-OH) that is hydrogen-bonded to the template
Replication forkDNA synthesis where the parental strands separate and two new daughter strands elongate - replication macromolecular complex
Leading strandsynthesized in a continuous manner in the direction of overall DNA replication
Lagging strandsynthesized in a discontinuous manner in the direction opposite of movement of the replication fork
Okazaki fragmentssmall pieces of newly synthesized DNA that are joined to form an intact new DNA strand in the lagging strand - 1000-3000 bp
Short fragments of RNA serve as?primers for DNA replication
PrimaseEnzyme that synthesizes short fragments of RNA (3-10 nucleotides) complementary to lagging strand template at replication fork (no 3’-OH required)
Exonuclease " enzyme activity that hydrolyzes (degrades) DNA/RNA molecules from their ends
Question Answer
RNase Hexonuclease that degrades the RNA strand of RNA-DNA hybrids in eukaryotes
DNA ligaseenzyme that seals breaks in DNA strands following replication
Clamp loading proteinsreplication factor C (RFC) in mammalian cells - loads clamp proteins onto replication fork at primer
Sliding clamp proteinse.g. proliferating cell nuclear antigen (PCNA) in mammalian cells - load and hold polymerase onto template
Helicasesenzymes that catalyze the unwinding of parental DNA (in ATP-dependent manner)
Single-stranded DNA-binding proteinsstabilize the unwound single-stranded template DNA.
TopoisomerasesEnzymes that catalyze reversible breakage & rejoining of DNA strands to relieve torsion caused by unwinding of DNA
Origins of replication (ori)serve as binding sites for the protein complex that initiates the replication process
Single originsdirect replication of bacterial and viral genomes - multiple origins are needed to replicate eukaryotic cells
Defects in Telomerase ActivitySomatic cells don't have enough telomerase for indefinite replications; we age, telomeres become shorter