Lecture 18 - DNA and RNA Structure 1

Question 1

What is the primary, secondary, and tertiary structure of DNA

Answer 1

Primary: nucleotide sequence
Secondary: usually right handed double helix
Tertiary: 3D folding

Question 2

What is a nucleotide

Answer 2

Nucleoside + phosphate or
sugar + phosphate + base
Nucleoside= sugar + base

Question 3

Where does the hydroxyl and the base and phosphate group attach?

Answer 3

Hydroxyl: 3’ on DNA, 2’ and 3’ on RNA
Phosphate: 5’ carbon, has -ve charge
base: 1’ carbon
nucleotides linked by phosphodiester linkage

Question 4

Distinguish between bases

Answer 4

Pyrimidines: have 1 ring (cytosine, thymine, uracil)
Purines: have 2 rings (adenosine, guanine)
Adenosine: has amino group
Guanine: has carbonyl group
Cytosine: has amino group
Thymine: has methyl group
Uracil: looks like thymine but doesn’t have methyl group
2 bonds between A-T
3 bonds between G-C

Question 5

Name the nucleosides

Answer 5

adenosine, guanosin, cytidine, thymidine, uridine

Question 6

What 2 forces hold DNA strands together?

Answer 6

1) hydrogen bonding between base pairs

2) base stacking –> Van der Waals interactions between hydrophobic bases to minimize contact with water

Question 7

Describe the major groove and minor groove

Answer 7

Major groove more exposed to solvent
Proteins search for specific sequence of DNA by reading exposed functional groups along major groove, serves as contact point

Question 8

Describe 2 other forms of DNA besides the B form

Answer 8

A form –> shorter, wider

Z form –> left handed, elongated