Key Words DNA polymerase Nucleotide Nucleus DNA Replication

Key Words DNA polymerase Nucleotide Nucleus DNA Replication LO Describe how DNA replicates itself Collect a white board and pen

Explain DNA replication in terms of unwinding of the double helix and separation of the strands by helicase, followed by formation of the new complimentary strands by DNA polymerase State that DNA replication occurs in a 5’-3’ direction Explain the process of DNA replication in prokaryotes, including the role of enzymes (helicase, DNA polymerase, RNA primase and DNA ligase), Okazaki fragments and deoxynucleoside triphosphates

DNA replication The discovery of DNA’s structure by Watson and Crick provided evidence that complementary base pairing was key to DNA’s ability to replicate. Scientists proposed that DNA ‘unzipped’ as hydrogen bonds between base pairs were broken. New polynucleotide strands could then be synthesized using the originals as a template. Several hypotheses were proposed as to the specific mechanism by which new strands are created. DNA replication occurs during (S phase of ) interphase in preparation for cell division;

DNA replication

Modelling DNA replication Gather around. .

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Hungry Ravenous Pigs Devour 31 Pineapples Loudly Gross Helicase RNA Primase DNA 3 and 1 Polymerase Ligase Gyrase

Single strand binding (SSB) protein, helicase enzyme, primase, DNA polymerase, parental DNA, lagging strand, DNA ligase, Okazaki fragments, replication fork, leading strand RNA primer

Single strand binding (SSB) protein DNA polymerase leading strand Helicase enzyme Replication fork RNA primer Primase Helicase enzyme Okazaki fragments DNA polymerase DNA ligase Parental DNA lagging strand

Cut up the information and stick it in the correct order to explain DNA replication

Explain the significance of complimentary base pairing in the conservation of the base sequence of DNA Complimentary base pairing between the template strand the new strand ensures that an accurate copy of the original DNA is made every time replication occurs.

State that DNA replication is semi-conservative Mechanisms of DNA replication

Meselson–Stahl DNA experiment

Complete the worksheet on experimental evidence on DNA

Summary DNA replication occurs during ________. DNA replication is_____________. The enzyme ________ unwinds the double helix and _______ bonds between the two strands are broken. Each strand of parent DNA used as a _______ for synthesis. Synthesis is continuous on leading strand but not continuous on lagging strand. This leads to the formation of ________fragments (on lagging strand). Synthesis occurs in the 5’ 3’ direction. RNA primer synthesized on parent DNA using__________ adds the nucleotides to the 3’ end added according to complementary base pairing. Adenine pairs with _________ and ______pairs with guanine. DNA polymerase I removes the RNA primers and replaces them with DNA. ________ joins Okazaki fragments as deoxynucleoside triphosphate joins with growing DNA chain, two phosphates broken off releasing energy to form bond

Summary DNA replication occurs during interphase. DNA replication is semi-conservative. The enzyme helicase unwinds the double helix and hydrogen bonds between the two strands are broken. Each strand of parent DNA used as template for synthesis. Synthesis is continuous on leading strand but not continuous on lagging strand. This leads to the formation of Okazaki fragments (on lagging strand). Synthesis occurs in the 5’ 3’ direction. RNA primer synthesized on parent DNA using RNA primase. DNA polymerase III adds the nucleotides to the 3’ end added according to complementary base pairing. Adenine pairs with thymine and cytosine pairs with guanine. DNA polymerase I removes the RNA primers and replaces them with DNA ligase joins Okazaki fragments as deoxynucleoside triphosphate joins with growing DNA chain, two phosphates broken off releasing energy to form bond

Think Box: Chromosomes in Eukaryotes and much longer than in prokaryotes. Suggest a way that eukaryotes could speed up the replication process Replication is initiated at many points in eukaryotic chromosomes! State that DNA replication is initiated at many points in eukaryotic chromosomes

Use the resources available to you to create your own step by step model of DNA replication. You will then be peer assessing each others attempts.

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