lecture 3 - minor nucleosides and polynucleotides

9 slides

when is modification done in nucleic acids?

done after DNA synthesis

what are the 3 factors of 5-methylcytosine?

1. common in eukaryotes

2. also found in bacteria

3. a way to mark which genes should be active

what are the 3 factors of N⁶-methyladenosine?

1. common in bacteria

2. not found in eukaryotes

3. a way to mark DNA so cells can degrade foreign DNA

what is inosine?

sometimes found in “wobble” position of anticodon in tRNA

what are 2 factors of inosine?

1. made by de-aminating adenosine

2. provides a richer genetic code

what is pseudouridine (Y)?

found widely in tRNA and rRNA

what are 4 factors of pseudouridine?

1. more common in eukaryotes

2. made from uridine by enzymatic isomerization after RNA synthesis

3. may stabilize structure of tRNA

4. may help in folding rRNA

what are 5 points of polynucleotides?

1. covalent bonds are formed via phosphodiester linkages - backbone is (-) charged

2. DNA is fairly stable - it’s hydrolysis is accelerated by enzymes (DNAse)

3. RNA backbone is relatively unstable

4. Linear polymers (no branching or cross-links)

5. Directionality (5’ end if different from 3’ end; read sequence 5’ → 3’)

what are 3 points of hydrolysis of RNA?

1. RNA is unstable under alkaline conditions

2. Hydrolysis is also catalyzed by enzymes (RNAse)

3. RNAse enzymes are abundant around us