Nucleic Acid as a Genetic material | Online Biotech Notes

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Nucleic Acid as a Genetic material

Until 1944 it was considered that protein is a genetic material, but certain experimental evidence proved that nucleic acid DNA is a genetic material.

1^st experiment evidence-

Transformation experiment:-

The initial experiment on transformation was performed by Frederick Griffith in 1928. He was working on two strains of streptococcus pneumonia.

 1).one strain is vrirulent , it cause disease, because it has polysaccharide capsule.

2). other strain is non vrirulent it does not cause disease because capsule is absent.

He name two strain as R11 and S11

R11-colony rough       =         Capsule absent     --->            Virulent non pathogenic

S111-Colony smooth  =         Capsule present    --->            Virulent pathogenic

Conclusion: - Heat S11 is somehow responsible for converting live R11 to live S111, by the process called transformation, but the natures of transformation is still unclear.

2^nd Experiment

• In 1944 Oswald T Avery, Colin M. Mac lead & Macleod McCarthy in United States explain the nature of transformation that is nucleic acid or DNA. Therefore nucleic acid or DNA us genetic material. He used & different enzymes in his expression

1.      Rnase ---- Destroy RNA

2.      Dnase ----- Destroy DNA

3.      Protease -----Destroy Proteins

Conclusion:-Nucleic acid is responsible for transformation, Hence Nucleic acid or DNA is Genetic material.

 

3^rd Experiment:-

• A third import an experiment provided independent evidence that DNA carries genetic information. In 1952 Alfred D.Hershey & Martha Chase.
• His experiment on Bacterial virus T2.
• T2 bacteria phages infect E.coli.
• It contains 50% nucleic acid & 50% proteins Nucleic acid contain phosphorous & protein contain surface.
• He radiolaballed DNA phosphorous with P³² & protein with S³⁵.

Conclusion:-P⁸² containing DNA enters into Bacterial cell & form now bacteria phage inside the bacterial cell, hence DNA code all the genetic information to form new bacteriophage inside the cell. Hence DNA is genetic material.

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