Lecture 3

Question 0

What are the properties of RNA?

Answer 0

Single stranded
Shorter than DNA
Soluble

Question 1

What are the three structures of nucleic acid?

Answer 1

Primary - sequence of nucleotides
Secondary - local folding (DNA double helix, structure of tRNA and rRNA)
Tertiary - long range folding; 3D structure - chromatin structure

Question 2

What gives RNA its secondary structure?

Answer 2

Local helical regions (hairpin loops) for,ex by the strand folding back to base pair with itself

Question 3

What are the secondary structure rules for RNA?

Answer 3

Folds into thermodynamically stable structure ie. Lowest energy structure
The most likely structure can be predicted but there are some simple rules;
- loops must have at least three unpaired nucleotides
- paired stems must have at least two AU or GC pairs
- GC pairs are more stable/likely than AU pairs because of H bonds
GU pairs are possible. Ut do not contribute to stability as they do not form H bonds

Question 4

What makes up 80% of RNA in a cell?

Answer 4

rRNA

Question 5

What is peptidyl transferase and where is the active site found?

Answer 5

The enzyme that catalyses formation of peptide binds - found in rRNA

Question 6

What is the tertiary structure known as in prokaryotes where the double helix further winds itself?

Answer 6

Supercoiling -
unwinding - right hand super helix - negative supercoiling
Overwinding - left handed superflex - positive supercoiling
Almost all DNA molecules in cells are negatively supercoiled

Question 7

How is eukaryotic DNA packaged?

Answer 7

Chromosomes - separate bodies each containing a single long, linear (open ends) DNA molecule
Chromatin - composed of DNA complexed with proteins (mainly histones) w
And has a strong positive charge

Question 8

What are the several levels of eukaryotic DNA structure?

Answer 8

Double helix
Supercoiling
Nucleosides
Solenoids
Loops
Chromosomes