Biology NUCLEIC ACIDS (RNA)

Wobble Hypothesis

`->` It was propounded by CRICK.

`->` Normally an anticodon recognises only one codon, but sometimes an anticodon recognises more than one codon. This is known as Wobbling. Wobbling normally occurs for third nucleotide of codon.

`->` For e.g. anticodon MG can recognise two codons i.e. `UUU` and `UUC`, both stands for phenyl alanine. Types of m-RNA - m-RNA is of 2 types -

(1) Monocistronic - The m - RNA in which genetic signal is present for the formation of only one polypeptide chain eg. Eukaryotes.

(2) Polycistronic :-Them-RNA, in which genetic signal is present for the formation of more than one polypeptide chains eg. Prokaryotes.

`->` Non sense codons are found in middle position in polycistronic m-RNA.

Central Dogma :

`->` Central dogma was given by Crick.

`->` The formation {production) of m- RNA from DNA and then synthesis of protein from it, is known as Central Dogma.

`->` It means, it includes transcription and translation.

Reverse Transcription :-

`->` The formation of DNA from RNA is known as Reverse - transcription. It was discovered by Temin and Baltimore in Rous - sarcoma virus. So it is also called Teminism.

`->` ss-RNA of Rous-Sarcoma virus (Retrovirus) produces ds-DNA in host's cell wiih the help of enzyme reverse transcriptase (DNA-polymerase). This DNA is called e-DNA (Complimentary DNA). Some times this DNA moves in host genome. Such mobile DNA is called "Retroposon" (Oncogene).