DNA: The Primary Source of Heritable Information. Genetic information is transmitted from one generation to the next through DNA or RNA

Transcription

1 DNA and Replication

2 DNA: The Primary Source of Heritable Information Genetic information is transmitted from one generation to the next through DNA or RNA

3 Chromosomes Non-eukaryotic (bacteria) organisms have circular chromosomes Eukaryotic organisms have multiple linear chromosomes Exceptions: Some bacterial cells have linear chromosomes Mitochondria and chloroplasts have been found to have circular and linear chromosomes

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5 Plasmids Prokaryotes, viruses and eukaryotes (yeast) may contain plasmids Plasmids are small extra-chromosomal, double-stranded circular DNA molecules Plasmids make excellent cloning vectors

6 Plasmids as Cloning Vectors

7 Important Historical Experiments The proof that DNA is the carrier of genetic information involved a number of important historical experiments, including: Frederick Griffith Avery-MacLeod-McCarty Hershey-Chase Watson, Crick, Wilkins and Franklin

8 Frederick Griffith Experiments in bacterial transformation Smooth (S) pathogenic bacteria Rough (R) nonpathogenic bacteria

9 ANIMATION Frederick Griffith Living bacterial cells were converted to disease causing bacteria (transformation) Transforming factor

10 Avery-MacLeod-McCarty Experiments Experiments demonstrated that DNA is the transforming material, not protein

11 Avery-MacLeod-McCarty Experiments Used different enzymes to destroy protein, RNA or DNA in separate tubes to determine if transformation occurs

12 Hershey-Chase Experiment Concluded that DNA, not protein, functions as the genetic material of phage T2

13 ANIMATION Hershey-Chase Experiment Tagged protein coat with radioactive sulfur Tagged viral genome with radioactive phosphorus

14 Erwin Chargaff Nitrogenous base composition % of adenine is equal to % of thymine % of guanine is equal to % cytosine Composition of DNA varies from species to species

15 Maurice Wilkins and Rosalind Franklin Worked with a technique called X-ray diffraction Determined the helical nature of DNA

16 James Watson and Francis Crick 1953 Determined the structure of DNA using Chargaff s and Franklin s data Franklin s picture showed two strands of nucleotides

17 DNA (Deoxyribonucleic acid) Nucleic acid Consists of monomers called nucleotides Stores genetic information, determines an organisms traits by synthesizing proteins Each organisms genome is unique

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19 ANIMATION Structure of DNA Double helix Consists of a double strand of nucleotides Two strands are anti-parallel: strands are oriented in opposite directions 5 to 3 3 to 5

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21 Nucleotide Composition Three parts of a nucleotide 5 carbon sugar called deoxyribose Phosphate group A single nitrogenous base

22 Four Nitrogenous Bases Purines (double ring) Adenine (A) Guanine (G) Pyrimidines (single ring) Thymine (T) Cytosine (C)

23 Purines pair with Pyrimidines

24 Chargaff s Rules A-T (2 hydrogen bonds) C-G (3 hydrogen bonds)

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26 DNA Replication

27 Why do cells need to replicate DNA?

28 ANIMATION Semi-Conservative Replication New DNA molecules have one original template strand and one new strand Follows complementary base pair rules and begins at sites called origins of replication Leading strand continuously synthesized Lagging strand synthesized in fragments

29 Semi-conservative Replication

30 Origin of Replication - Prokaryotes

31 Origins of Replication - Eukaryotes

32 Replication Bubbles

33 Enzyme Functions Helicase RNA Primase DNA Polymerase III DNA Polymerase I DNA Ligase Topoisomerase Single-strand binding proteins (not an enzyme)

34 Replication Direction Replication proceeds in the 5 to 3 direction DNA polymerase can only add free nucleotides to the 3' end of the newly forming strand

35 ANIMATION More animations for your viewing pleasure. DNA Replication Animation Steps of DNA Replication