DNA replication

Emily Sutton
Flashcards by Emily Sutton, updated more than 1 year ago
Emily Sutton
Created by Emily Sutton over 5 years ago
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AS - Level Biology (Nucleic acids and their functions) Flashcards on DNA replication, created by Emily Sutton on 02/25/2016.

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Question Answer
Nucleic acids - DNA replication Semi-conservative replication = partially keeps (conserves) part of the original strand
Semi conservative replication: 1) dna molecule begins to unwind 2) hydrogen bonds between bases break, exposing bases, it unzips 3) each strand of dna acts as a template for the formation of new complementary strand
4) free activated dna nucleotides in nucleus are attracted to their complementary exposed base (A-T and C-G) and link by hydrogen bonds 5) dna polymerase catalyses the condensation reactions between deoxyribose and phosphates of adjacent nucleotides to form a sugar phosphatebackbone 6) two identical dna molecules formed, each containing an old parent strand and one new strand This is semi-conservative replication
Other theories of dna replication Meselsohn and Stahl - landmark experiment to support theory proposed by Watson and Crick
1) They chose bacteria as replicate every 20 minutes 2) 2 isotopes of nitrogen (N15 and N14) in growth medium (food for bacteria) so they could identify which were new nucleotides and which were in original DNA molecule. The N used to make the nitrogenous bases 3) N15 (labelled N) is a slightly heavier atom than N14 4) The bases and the way they pair not affected by different isotope
5) A density gradient can be produced by centrifuging Caesium Chloride (CsCl) at very high speed overnight 6) If DNA is also placed in tube it will remain intact and settle at point where it’s density equals that of the CsCl
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