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Ch. 25.1 (part 2)

Ch. 25.1 (part 2). DNA Structure & Replication. Target #7- I can explain what Rosalind Franklin discovered about DNA. Rosalind Franklin Studied DNA using x-ray crystallography The DNA, when bombarded with x-rays, an image can be captured from the refracted light

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Ch. 25.1 (part 2)

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  1. Ch. 25.1 (part 2)

    DNA Structure & Replication
  2. Target #7- I can explain what Rosalind Franklin discovered about DNA Rosalind Franklin Studied DNA using x-ray crystallography The DNA, when bombarded with x-rays, an image can be captured from the refracted light X-ray photographs showed an X surrounded by a circle Used later by James Watson & Francis Crick to further develop the shape of DNA
  3. James Watson & Francis Crick One of the many scientists to study proteins and the structure of DNA Built a model of DNA using wood and metal Found that DNA fits together like a puzzle Double Helix: two strands of DNA wind around each other like a twisted ladder Target #8- I can explain what Watson & Crick discovered about DNA
  4. Target #9- I can describe the structure of DNA A DNA strand: Has a backbone made up of alternating phosphate and sugar molecules Has two strands which form a double helix Held together by hydrogen bonds Run anti-parallel In opposite directions Top carbon on left strand is labeled 5’ Top carbon on right strand is labeled 3’
  5. Target #10- I can explain the structure of nucleotides DNA is a chain of nucleotides Made of 3 subunits: phosphate group, pentose sugar, nitrogen base Purines a group of nitrogen bases Adenine Guanine Pyrimidines a group of nitrogen bases Thymine cytosine
  6. Target #11- I can state complimentary base pairing rules Complimentary base pairing rules A always pairs with T Forms 2 hydrogen bonds G always pairs with C Forms 3 hydrogen bonds
  7. Target #12- I can describe DNA replication DNA replication: the process of copying one DNA double helix into two identical double helices Each original strand serves as a template for the formation of a complimentary new strand Known as “semiconservative” A new double helix has one conserved old strand and one new strand Results in two new DNA helices that are identical to each other and to the original molecule
  8. Target #13- I can state what occurs during DNA replicationTarget #14- I can identify the enzymes involved with DNA Replication Step 1: before replication begins the two strands that make up parental DNA are hydrogen bonded to each other Step 2: The enzyme DNA helicase unwinds and “unzips” the double stranded DNA at the replication fork Breaks the hydrogen bonds Step 3: New complimentary DNA nucleotides fit into place via base pairing Joined by the enzyme DNA polymerase 5’ strand is leading strand Replication occurs “forwards” 3’ strand is lagging strand Replication occurs “backwards”
  9. Target #13 & #14- cont. Step 4: To complete replication, the enzyme DNA ligase seals any breaks in the sugar phosphate backbone Step 5: the two double helix molecules are identical to each other and the original DNA molecule
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