RNA And The 3 Major Groups

Question 1

RNA and the 3 major groups

Answer 1

-are unbranched polymers of nucleoside monophosphate joined by 3’ - 5’ phosphodister bonding
-Has three major groups ( which all participate in protein synthesis )
1 messenger RNA
2 transfer RNA
3 ribosomal RNA

Question 2

Differences of RNA and DNA

Answer 2

• RNA is smaller
• made of ribose instead of deoxyribose
• uracil instead of thymine
• exist as single Strands capable of folding into complex structures

Question 3

rRNA

Answer 3

• 80% of cell RNA
• found in association with other proteins as components of ribosomes ( it makes the core )
• some are catalysts eg rRNA in protein synthesis
• aid in binding of mRNA to ribosomes for translation

Question 4

Svedberg units S

Answer 4

-unit of sedimentation rate. Determined by size and shape of particle

Question 5

tRNA

Answer 5

• smallest RNA ( 4S ) and 15% in cells and generated by nuclear processing of precursor molecule
• one specific tRNA for the 20 amino acids in proteins.
• high percentage of unusual base pairs and extensive inter-chain’s forming characteristic secondary and tertiary structure
• each tRNA is an adaptor molecule carrying bits specific amino acid covalently bonded to its 3’ end to the site of protein synthesis
• at ribosomes it recognizes genetic code sequence on mRNA which specifies its addition of amino acid to peptide

Question 6

tRNA arms

Answer 6

-acceptor arm attaches aa to its 3’ OH end of the A moiety (- CCA -)
- D ( dihydrouracil ) A ( anticodon )/ extra arms and T(Poseidon) C ( thymine / pseudouracil / cytosine ) determine a specific tRNA
-

Question 7

mRNA

Answer 7

• 5% in cells and most heterogeneous in terms of size and shape
• carries genetic sequence form DNA into cytosol and serves as template on which a specific sequence of aas is polymerized at ribosomes
• in addition to coding regions also has untranslated regions at 3’ and 5’ end ( untranslated 3’ trailing end and untranslated 5’ leading end )

Question 8

Polycistronic and Mono

Answer 8

• mRNA carrying more than one gene ( prokaryotes)

- mRNA carrying one gene ( eukaryotes)

Question 9

Special characteristics of eukaryotes mRNA

Answer 9

-long sequence of adenosine nucleotides ( Poly A tails ) at 3’ end and cap of 7-methylguanosine at 5’ end attached through unusual 5’-5’ phosphodister bond

Question 10

Use of mRNA cap

Answer 10

-recognized by translational machines

Question 11

hnRNA

Answer 11

• mRNA In cytoplasm isn’t RNA immediately synthesized from DNA by formed by processing of precursor ( hnRNA )
• hnRNA is the immediate product of gene transcription and processed to generate mRNA which enters cytoplasm to serve as templates for protein synthesis