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Chapter 10 Notes Structure of DNA
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DNA is Made up repeating units of nucleotides Three parts of a Nucleotide are: 1. Deoxyribose sugar 2. Phosphate group 3. Nitrogen-containing base
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Nitrogen Containing Bases
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Base Pairing Rules Adenine pairs with Thymine (2 hydrogen bonds) Guanine pairs with Cytosine (3 hydrogen bonds) Chargaff’s Rule: The amount of adenine always equals the amount of thymine, and the amount of guanine equals cytosine.
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The Double Helix Double stranded, coiled like a spiral stair The backbone of the strands are alternating phosphate and deoxyribose sugars
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Histones DNA is tightly coiled around proteins called histones to make the long DNA molecule easier to manage.
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What are the three parts of a nucleotide?
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What Base Bonds to Adenine?
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What Base Bonds to Guanine?
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Assignment Class work: DNA Book– cover page and page 1 (Due tomorrow) Homework: PQRST pg. 200- 203 (due Friday)
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Purpose of DNA Replication Why would DNA replicate? When would DNA replication occur? To make a copy of it’s DNA for the cell to divide. Mitosis
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Steps of DNA Replication 1. Helicase unzips and unwinds the DNA strands by breaking the hydrogen bonds
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Steps of DNA Replication 2. Enzymes called DNA Polymerase add complementary nucleotides.
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Steps of DNA Replication 3. Process continues until entire strand is copied Result is two strands of DNA
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AA TCC AAA G A TTTTT GG C 1. First the DNA must unzip: Enzymes split apart the base pairs and unwind the DNA.
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AA TCC AAA G A TTTTT GG C
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AA TCC AAA G A TTTTT GG C
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AA TCC AAA G A TTTTT GG C T T 2. Bases pair up: Free nucleotides in the cell find their complementary bases along the original strand.
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AA TCC AAA G A TTTTT GG C T A CT
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AA TCC AAA G A TTTTT GG C T A CT A T
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AA TCC AAA G A TTTTT GG C T A CT A T C G
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AA TCC AAA G A TTTTT GG C T A CT A T C G A C A T G TT G
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AA TCC AAA G A A TTTTT GG C T A CT A T C G A C A T G TT G A
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AA TCC AAA G A A TTTTT GG C T A CT A T C G A C A T G TT G A The DNA is now duplicated:
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End Result Two identical molecules of DNA They have one new and one old strand
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Mechanism of DNA Replication DNA is said to be semiconservative since each new DNA molecule made has one parent strand and one daughter strand. Can also be said: one old strand and one new strand
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Accuracy and Repair Copies must be 100% accurate Mutation= change in nucleotide at one location Enzymes proofread and fix errors
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Class work Homework DNA Replication worksheet 1. Answer questions at the top 2. Use page 201 to create a labeled drawing of DNA Replication with descriptions of each step Page 2 of DNA Book (due Monday) PQRST (due tomorrow)
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