2.1 Lecture

Question 1

Pyramidine

Answer 1

six-member single aromatic ring with
nitrogen at the 1 and 3 positions

Question 2

How do nucleotides link into nucleic acid chains?

Answer 2

phosphodiester bond linkages

Question 3

Why is RNA so much less stable than DNA?

Answer 3

is because of the main structural difference between
them – the C2’ hydroxyl group!
This C2’ hydroxyl group acts as a nucleophile in a displacement reaction – the
phosphate group linking the two nucleotides instead forms a bond with C2’ OH
This breaks the RNA chain at that position

Question 4

Which is bigger the minor or major groove?

Answer 4

Major grooves are about 1.5 times the width of minor grooves

Question 5

Depurination

Answer 5

Loss of the
purine base through hydrolysis

Question 6

Deamination

Answer 6

cytosine is deaminated to make
uracil, this site that should normally base
pair with guanine instead base pairs with
adenine, causing a permanent mutation!

Question 7

Thymine dimers

Answer 7

Occur when UV
light catalyzes formation of a cyclobutyl
ring involving C5 and C6 of adjacent
pyrimidine residues (usually thymine)
This disrupts normal base pairing
This is why UV light can cause cancer!

Question 8

What is RNA editing?

Answer 8

when genetic information is
altered from the genomic blueprint
The most common RNA edit is Deamination of adenosine to inosine

Question 9

Wobble base pairing

Answer 9

Before editing, adenine at a given site can only base pair with uracil; after
editing, inosine at that site can base pair with uracil, adenine or cytosine

Question 10

What is a riboswitch

Answer 10

A riboswitch is a secondary structural element in mRNA that binds ligands
to regulate mRNA transcription, splicing or translation