Section 14 RNA

14.1  Structure of RNA

Sequence of nucleotides in DNA determines sequence of AAs

DNA must be transferred from the nucleus to the cytoplasm where protein synthesis occurs by transferring code into single strand RNA

Messenger RNA - thousands of mono nucleotides - single strand helix leaves nucleus through membrane pore - associates with ribosomes - exists only once.

Transfer RNA - 80 nucleotides - single strand clover leaf - one end is longer than the other so that AA can attach - each carry single AA - other end 3 organic bases form anti codon. 

Features of genetic code- codon 3 base pairs code for AA - degenerate - most amino acids have more than one codon - 3 codons, no AA, stop codon - non overlapping - universal same codon for same AA in in all organisms .

RNA structure - polymer repeating mono nucleotides - pentose sugar - organic base (AGCU)

14.2 Transcription

Pre RNA uses DNA as a template.

DNA helicase acts on H bonds between strands separating them. 

RNA polymerase moves along one of the strands attaching nucleotides.

A joins U - nucleotides added one at a time - DNA rejoins behind - 22 base pairs exposed at once 

RNA polymerase detaches at stop codon.

Splicing - exons useful - introns…