MOLECULAR BASIS OF INHERITANCE (part1)

Molecular basis of inheritance

    

 living system  has two  nucleic acid

1. DNA  which act as  genetic material

2.   RNA  which act as 

 •genetic material in some virus 

 •messenger

 •adaptor

 •structural

 •catalytic molecule

-> Transcription :  process making RNA from DNA

-> Translation:  process of protein synthesis

 

☆ Genetic material:  it is the substance that controls the inheritance of traits from one generation to the next generation.

 ☆ The search for genetic material☆            ▪︎Nuclein  discovered Meisher

▪︎ Principles of inheritance discovered by Mendel at the same time

   ▪︎chemical natureof genetic material was unknown until 1926

-> Transforming principle : 

 1928-  Frederick Griffith experiment with Streptococcus pneumoniae ( bacteria responsible for pneumonia) also called diplococcus pneumoniae. 

 Streptococcus pneumoniae produce

1.   S strain bacteria which is smooth  Shiny colonies(  virulent)  cause S strain bacteria have a mucus (polysaccharide) coat.

 2.  R strain bacteria  which is rough (non-virulent)  are strain bacteria does not have mucus or polysaccharide  coat .

 ▪︎ S strain bacteria -  injected into mice -  mice died  ( virulent )

▪︎  R strain bacteria -   injected - mice live ( absence of bacteria)

▪︎ Heat killed virulent S - injected - mice live 

▪︎S (heat killed) + R (living) - mice died (virulent) 

 ☆ S bacteria recovered from the dead mice.  

CONCLUSION: 

1. R strain  bacteria has been transformed by heat killed S strain bacterium.  

2. S strain - (transforming principal) - R strain- expressing/ development of smooth polysaccharide coat - R strain become virulent. 

• But biochemical nature of genetic material was unknown.  

MOUSMI SHRIVASTAVA.