DNA replication

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Flashcards by lumen7, updated more than 1 year ago
lumen7
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Genetics Flashcards on DNA replication, created by lumen7 on 05/11/2013.

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Question Answer
what is the role of the DNA replication fork? the region of DNA at which all proteins involved in DNA replication come together to carry out synthesis of daughter strands (party central)
2 strands of DNA replication leading and lagging
leading strand made continuously from a single RNA primer
lagging strand made discontinuously- new primer made every few hundred bases
Okazaki fragments 1. formed on the lagging template between 100 and 200 nucleotides long. 2. separated by ~10-nucleotide RNA primers and are unligated until RNA primers are removed
what maintains the stability of the replication fork? single stranded binding proteins (RPA) - also stops ssDNA from being degraded by exonucleases
PCNA 3 subunits form a circular structure through which DNA passes -maintains the stability of polymerase
bi-directional mechanism of DNA replication two forks form at origin and move in opposite directions-both strands being copied in each direction
telomeres repetitive sequence at end of chromosomes -protect from fraying
the 4 enzymes of DNA replication 1. helicase, 2. DNA polymerase, 3. primase, 4. ligase
helicase unwinds the double strand, this requires energy to break the H bonds
3 DNA polymerase jobs 1.copies the strand. 2. moves along the single strands and recruits dNTPs (nucleotide triphospates) to hydrogen bond their partners and helps build a second strand. 3. removes errors
primase an RNA polymerase that is part of an aggregate of proteins called the primeosome. Attaches a small RNA primer to the ssDNA to act as a primer for synthesis (removed later by RNase H)
ligase joins together two pieces of DNA when DNA polymerase I fills the gaps
what enzyme is responsible for synthesis? DNA polymerase
2 requirements for DNA polymerase to work 1. needs a primer with a free 3'OH group, 2. it can only act 5'3' direction
DNA polymerase structure highly conserved. The shape can be described as resembling a right hand with thumb, finger and palm domains.
why do we need DNA replication? in order to copy chromosomes exactly before cell division to ensure new daughter cells have same content
origin of replication the point at which the DNA unwinds and the primer binds, usually A-T rich regions
the DNA synthesied from the origin of replication is called a replicon
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