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Conservative Vs Semiconservative Vs Dispersive

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Agreement:

•  The replication of DNA is semi-conservative and depends on complementary base pairing


Deoxyribonucleic acid replication is a semi-conservative process, because when a new double-stranded Deoxyribonucleic acid molecule is formed:

  • I strand will be from the original template molecule
  • One strand will be newly synthesised

Semi-Conservative Deoxyribonucleic acid Molecule

semi-conservative DNA

This occurs because each nitrogenous base can only pair with its complementary partner

  • Adenine (A) pairs with thymine (T)
  • Cytosine (C) pairs with guanine (K)


Consequently, when Dna is replicated by the combined activity of helicase and DNA polymerase:

  • Each new strand formed will be identical to the original strand separated from the template
  • The 2 semi-conservative molecules formed will take an identical base of operations sequence to the original molecule

Conservation of Sequence by Complementary Base Pairing

semi-conservative base pairing

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Skill:

•  Analysis of Meselson and Stahl'southward results to obtain support for the theory of semi-conservative replication of DNA


The theory that DNA replication was semi-bourgeois was confirmed by the Meselson-Stahl experiment in 1958


Prior to this experiment, three hypotheses had been proposed for the method of replication of DNA:

  • Conservative Model – An entirely new molecule is synthesised from a Deoxyribonucleic acid template (which remains unaltered)
  • Semi-Bourgeois Model – Each new molecule consists of one newly synthesised strand and one template strand
  • Dispersive Model – New molecules are fabricated of segments of new and old Deoxyribonucleic acid

Three Proposed Models of Dna Replication

Models of replication

Meselson and Stahl were able to experimentally examination the validity of these three models using radioactive isotopes of nitrogen

  • Nitrogen is a key component of DNA and can exist equally a heavier fifteen North or a lighter 14 N


Deoxyribonucleic acid molecules were prepared using the heavier 15N so induced to replicate in the presence of the lighter xivNorthward

  • Dna samples were and then separated via centrifugation to decide the limerick of DNA in the replicated molecules


The results after ii divisions supported the semi-conservative model of DNA replication

  • Later ane division, Dna molecules were found to contain a mix of 15Northward and 14North, disproving the conservative mod el
  • After 2 divisions, some molecules of DNA were found to consist solely of fourteen Northward, disproving the dispersive model

Results of the Meselson-Stahl Experiment

meselson-stahl

Conservative Vs Semiconservative Vs Dispersive,

Source: http://ib.bioninja.com.au/standard-level/topic-2-molecular-biology/27-dna-replication-transcri/semi-conservative.html

Posted by: jamesfourgaver.blogspot.com

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