DNAStructure and Replication
DNA STRUCTURE
History of DNA   Early on, protein thought as the cell’s hereditary material   because it was more complex than DNAFred Gr...
History of DNA               Radioactive   32P   was injected into bacteria!Chromosomes are made of both DNA and proteinEx...
Chargaff’s Rule  Adenine must pair with Thymine  Guanine must pair with CytosineThe bases form weak hydrogen bondsT       ...
James Watson (L) and FrancisCrick (R), and the model they built of thestructure of DNA                   AS Biology. Gneti...
HelixMost DNA has a right-hand twist with 10 basepairs in a complete turnLeft twisted DNA iscalled Z-DNA orsouthpaw DNAHot...
The structure of DNA and RNA Genetic material of living organisms is either DNA or RNA.  DNA – Deoxyribonucleic acid  RNA ...
DNA and RNA are polynucleotides       Both DNA and RNA are polynucleotides.       They are made up of smaller molecules ca...
Structure of a nucleotide2.A Phosphate group   Phosphate groups                                    P  are important  becau...
Structure of a nucleotide3. A Nitrogenous base  In DNA the four bases are:                               P     Thymine    ...
Sugar phosphate bonds (backbone of DNA) Nucleotides areconnected to eachother via thephosphate on onenucleotide and thesug...
Nitrogenous bases – Two types   Pyrimidines                                               Purines   Have single ring      ...
Adenine          AS Biology. Gnetic control of protein structure
Guanine          AS Biology. Gnetic control of protein structure
Cytosine           AS Biology. Gnetic control of protein structure
Base pairingSides made of a pentosesugar deoxyribosebonded to phosphate(PO4) groups byphosphodiester bondsCenter made of n...
AS Biology. Gnetic control of protein structure
AS Biology. Gnetic control of protein structure
Again:Adenine always base pairs with Thymine (or Uracil ifRNA)Cytosine always base pairs with Guanine.This is because ther...
Nature of the Genetic Material1. It must contain, in a stable form, informationencoding the organism’s structure, function...
DNA     5       O                                           3         3                                               OP  ...
Antiparallel Strands One strand of DNAgoes from 5’ to 3’(sugars) The other strand isopposite indirection going 3’to 5’ (su...
Question:  What would be the complementary DNA strand for the following DNA sequence? DNA 5’-CGTATG-3’        copyright cm...
Answer:DNA 5’-CGTATG-3’DNA 3’-GCATAC-5’     copyright cmassengale   27
Dna structure
Dna structure
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Dna structure

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Dna structure

  1. 1. DNAStructure and Replication
  2. 2. DNA STRUCTURE
  3. 3. History of DNA Early on, protein thought as the cell’s hereditary material because it was more complex than DNAFred Griffith worked with virulent S and nonvirulent R strain Pneumoccocus bacteria.He found that R strain could become virulent when it took in DNA from heat-killed SstrainStudy suggested that DNA was probably the genetic material copyright cmassengale 3
  4. 4. History of DNA Radioactive 32P was injected into bacteria!Chromosomes are made of both DNA and proteinExperiments on bacteriophage viruses by Hershey& Chase proved that DNA was the cell’s geneticmaterial Discovery of DNA StructureErwin Chargaff showed the amounts of the four bases onDNA ( A,T,C,G)In a body or somatic cell: A = 30.3% T = 30.3% G = 19.5% C = 19.9% copyright cmassengale 4
  5. 5. Chargaff’s Rule Adenine must pair with Thymine Guanine must pair with CytosineThe bases form weak hydrogen bondsT A G C copyright cmassengale 5
  6. 6. James Watson (L) and FrancisCrick (R), and the model they built of thestructure of DNA AS Biology. Gnetic control of protein structure
  7. 7. HelixMost DNA has a right-hand twist with 10 basepairs in a complete turnLeft twisted DNA iscalled Z-DNA orsouthpaw DNAHot spots occur whereright and left twistedDNA meet producingmutations copyright cmassengale 7
  8. 8. The structure of DNA and RNA Genetic material of living organisms is either DNA or RNA. DNA – Deoxyribonucleic acid RNA – Ribonucleic acid Genes are lengths of DNA that code for particular proteins.
  9. 9. DNA and RNA are polynucleotides Both DNA and RNA are polynucleotides. They are made up of smaller molecules called nucleotides. Nucleotide DNA is made of two polynucleotide strands: Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide RNA is made of a single polynucleotide strand: Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide AS Biology. Gnetic control of protein structure
  10. 10. Structure of a nucleotide2.A Phosphate group Phosphate groups P are important because they link the sugar on one nucleotide onto the S phosphate of the next nucleotide to make a polynucleotide. AS Biology. Gnetic control of protein structure
  11. 11. Structure of a nucleotide3. A Nitrogenous base In DNA the four bases are: P Thymine N-base Adenine Cytosine Guanine In RNA the four bases are: S Uracil Adenine Cytosine Guanine AS Biology. Gnetic control of protein structure
  12. 12. Sugar phosphate bonds (backbone of DNA) Nucleotides areconnected to eachother via thephosphate on onenucleotide and thesugar on the nextnucleotide A Polynucleotide
  13. 13. Nitrogenous bases – Two types Pyrimidines Purines Have single ring Have double rings of Carbon and Nitrogen Thymine - T atom Cytosine - C Uracil - U Adenine - A Guanine - GBase-Pairings: Purines only pair with Pyrimidines AS Biology. Gnetic control of protein structure
  14. 14. Adenine AS Biology. Gnetic control of protein structure
  15. 15. Guanine AS Biology. Gnetic control of protein structure
  16. 16. Cytosine AS Biology. Gnetic control of protein structure
  17. 17. Base pairingSides made of a pentosesugar deoxyribosebonded to phosphate(PO4) groups byphosphodiester bondsCenter made of nitrogenbases bonded together byweak hydrogen bonds Adenine links with Thymine or Uracil by 2 hydrogen bonds Cytosine links with Guanine by 3 hydrogen bonds AS Biology. Gnetic control of protein structure
  18. 18. AS Biology. Gnetic control of protein structure
  19. 19. AS Biology. Gnetic control of protein structure
  20. 20. Again:Adenine always base pairs with Thymine (or Uracil ifRNA)Cytosine always base pairs with Guanine.This is because there is exactly enough room for onepurine and one pyrimidine base between the twopolynucleotide strands of DNA. Complementary Base Pairing
  21. 21. Nature of the Genetic Material1. It must contain, in a stable form, informationencoding the organism’s structure, function,development and reproduction2. It must replicate accurately so progeny cells havethe same genetic makeup3. It must be capable of some variation (mutation) topermit evolution AS Biology. Gnetic control of protein structure
  22. 22. DNA 5 O 3 3 OP 5 P 5 O 1 G C 3 2 4 4 2 1 3 5P O P 5 T A 3 O O 5P 3 P copyright cmassengale 24
  23. 23. Antiparallel Strands One strand of DNAgoes from 5’ to 3’(sugars) The other strand isopposite indirection going 3’to 5’ (sugars) copyright cmassengale 25
  24. 24. Question: What would be the complementary DNA strand for the following DNA sequence? DNA 5’-CGTATG-3’ copyright cmassengale 26
  25. 25. Answer:DNA 5’-CGTATG-3’DNA 3’-GCATAC-5’ copyright cmassengale 27
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