Question

tRNA, rRNA, and sn RNA are all formed by:

Answer 1

tRNA, rRNA and snRNA are all formed by DNA by process called Transcription.

The process by which RNA is synthesised from DNA is called transcription.

Salient features of transcription:

a. Template strand and coding strand : the strand that is transcribed or copied to mRNA is called template strand or nonsense strand. The opposite strand is called as coding strand or non template strand.

New RNA is synthesised in 5' to 3 direction.

No primer is required.

Only a part of DNA strand is transcribed.

Steps of Transcription( formation of RNA form DNA) :

1.Template strand and closed RNA polymerase promoter complex formation.

2.open promoter complex formation.

3.chain initiation.

4.promoter clearence.

5.chain elongation.

6.chain termination and RNAP release.

Types of RNA:

1.mRNA: most heterogenous RNA.

Function as messenger conveying information to translation machinery. 2-5% of total celular RNA.

2.rRNA:most abundunt RNA. It forms the protein synthesising machinery called ribosome.

3.tRNA: RNA which transfers amino acid from the cytoplasm to ribosomal protein synthesis machinary.. It is clover leaf shape in secondary structure. L shaped tertiary structure.

4.Sn RNA : they belong to small RNA of size 90 to 300 nucleotides. 1% of total RNA. They have ribozyme activity.