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Lesson 2

Lesson 2: DNA Structure, Replication and DNA Repair Enzymes

Lesson parts

2.1 The structure of DNAThe structure of DNA2.1

2.2 The data a model had to fitThe data a model had to fit2.2

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2.3 The Watson–Crick modelThe Watson–Crick model2.3

2.4 Why the model fits the dataWhy the model fits the data2.4

2.5 Worked example 3 — complementary strandWorked example 3 — complementary strand2.5

2.6 Worked example 4 — base percentagesWorked example 4 — base percentages2.6

2.7 Worked example 5 — a test for the type of nucleic acidWorked example 5 — a test for the type of nucleic acid2.7

2.8 Why replicate?Why replicate?2.8

2.9 The steps and the enzymesThe steps and the enzymes2.9

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2.10 Where replication startsWhere replication starts2.10

2.11 Summary of the enzymesSummary of the enzymes2.11

2.12 Worked example 6 — template and productWorked example 6 — template and product2.12

2.13 Worked example 7 — how many fragments?Worked example 7 — how many fragments?2.13

2.14 Worked example 8 — speed of copyingWorked example 8 — speed of copying2.14

2.15 DNA damage and repairDNA damage and repair2.15

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2.16 Worked example 9 — why does RNA virus mutate more?Worked example 9 — why does RNA virus mutate more?2.16

2.17 ProkaryotesProkaryotes2.17

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2.18 Eukaryotes – chromatin and condensationEukaryotes – chromatin and condensation2.18

2.19 ComparisonComparison2.19

2.20 Worked example 10 — packing ratioWorked example 10 — packing ratio2.20

2.21 The genomeThe genome2.21

2.22 Repetitive DNARepetitive DNA2.22

2.23 Worked example 11 — reasonsWorked example 11 — reasons2.23

2.24 DefinitionDefinition2.24

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2.25 KindsKinds2.25

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2.26 Gamete and somatic mutationsGamete and somatic mutations2.26

2.27 Origin of mutationsOrigin of mutations2.27

2.28 Worked example 12 — classifyWorked example 12 — classify2.28

2.29 Key termsKey terms2.29

2.30 Final recapFinal recap2.30

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