Discovery ofDNA:1869-Friedrich Miescherextracted a weakly acidic,phosphorous-richmaterial from nuclei ofhuman white blood cellswhich he named nuclein6-6
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 6-6 1869 – Friedrich Friedrich Miescher Miescher extracted a weakly acidic, extracted a weakly acidic, phosphorous phosphorous-rich material from nuclei of material from nuclei of human white blood cells human white blood cells which he named which he named nuclein nuclein. Discovery of DNA: Discovery of DNA:
-NucleotideDNA-deoxyribonucleicacidFour nucleotide subunitslinked together byphosphodiester bondsDeoxyribosePolymersugarNitrogenous BasePhosphatePhosphodiesterbonds-NucleotideFig.6.2
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 6-7 DNA – deoxyribo eoxyribonucleic acid Four nucleotide subunits Four nucleotide subunits linked together by linked together by phosphodiester phosphodiester bonds. Nitrogenous Base Fig. 6.2
Evidence favoringDNA as the genetic material was firstobtained during the study of bacteria and bacteriophagesTransformation studies:1928-FrederickGriffith published his experiment with smooth(S), virulent strain Streptococcus pneumoniae, and rough (R),nonvirulentstrainPolysaccharidecapsuleLivingRformRoughcolonySmoothcolonyLivingSformFig.6.36-8
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 6-8 1928 – Frederick Griffith Frederick Griffith published his experiment with smooth published his experiment with smooth (S), virulent strain (S), virulent strain Streptococcus Streptococcus pneumoniae pneumoniae, and rough (R), , and rough (R), nonvirulent nonvirulent strain. strain. Polysaccharide capsule Fig. 6.3 Transformation studies: Evidence favoring DNA as the genetic material was first Evidence favoring DNA as the genetic material was first obtained during the study of bacteria and obtained during the study of bacteria and bacteriophages bacteriophages
(b)InjectDeaMutatestoAliveInjectCellInjectHeat-killedcomponentsAliveCellHeat-killedcomponentsTissueanalyzedCombinedInjectDeadLiving SOrecoveredFig.6.46-9
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 6-9 Fig. 6.4
Conclusion from Griffith's experiment:Genetic information from dead bacterial cells could betransmittedto livecellsTransformation-One of the mechanisms that bacteriatransfer genes from one strain to another.Transformation occurred in the animal body6-10
Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 6-10 Genetic information from dead bacterial cells could be transmitted to live cells. Transformation – One of the mechanisms that bacteria transfer genes from one strain to another. Transformation occurred in the animal body. Conclusion from Griffith’s experiment: