DNA Structure

Question 1

What year was the Nobel Prize given for the discovery of DNA structure?

Answer 1

1953

Question 2

Who won the Nobel Prize for discovering the structure of DNA?

Answer 2

James Watson
Francis Crick
Maurice Wilkins

Question 3

Who actually got the evidence on the structure of DNA and had her research stolen?

Answer 3

Rosalind Franklin

Question 4

What is the difference between a nucleoside and a nucleotide?

Answer 4

Nucleoside = base bound to sugar
Nucleotide = base bound to sugar and phosphate

Question 5

What is the bond between the sugar and the base?

Answer 5

glycosidic bond

Question 6

What is the bond between the phosphate group and the sugar-base?

Answer 6

phosphoester bond

Question 7

What is the name of the stand alone sugar in DNA?

Answer 7

2’ - deoxyribose

Question 8

What rxn is taking place to combine phosphoric acid, 2’ -deoxyribose, and the base into a nucleotide?

Answer 8

dehydration reaction

Question 9

Who discover base pairings and how?

Answer 9

Erwin Chargaff

Tested molar ratios of bases and found equivalent amounts of guanine to cytosine and adenine to thymine.

Question 10

What bond makes up the DNA backbone of each strand?

Answer 10

Phosphodiester linkage

Question 11

What does it mean when the 2 DNA strands run 5’ to 3’ and the other 3’ to 5’?

Answer 11

The 2 strands run anti-parallel to each other.

Question 12

What is the difference between a purine and a pyrimidine?

Answer 12

Purine = 5 member ring + 6 member ring (larger)
Pyrimidine = 6 member ring (smaller)

Question 13

What are the purines?

Answer 13

Guanine and Adenine

Question 14

What are the pyrimidines?

Answer 14

Cytosine and Thymine

Question 15

What are the 4 bases?

Answer 15

Guanine
Thymine
Cytosine
Adenine

Question 16

What are the complimentary bases and how many bonds do they form?

Answer 16

Guanine to Cytosine = 3 H bonds

Adenine to Thymine = 2 H bonds

Question 17

What are the tautomeric states?

Answer 17

Pyrimidines = Amino  Imino
Purine = Keto  Enol

Question 18

Which tautomeric states are in major access at equilibrium?

Answer 18

Amino and Keto

Question 19

Why are tautomeric states important?

Answer 19

The minor forms can be a large source of mutations due to inappropriate bonds forming.

Question 20

What are the 3 ways the double helix is stabilized?

Answer 20

1. Hydrogen bond pairing
2. Base stacking
3. Phosphate backbone

Question 21

How are Hydrogen bond pairing and base stacking important to double helix stabilization?

Answer 21

Both create a hydrophobic environment. H2O is displaced by the hydrogen bond pairing
The base stacking is hydrophobic when in the double stranded formation and the planar bases stack on top of each other to exclude water.
Without water, the reactivity lowers (increased entropy) within in the internal environment.

Question 22

How does the phosphate backbones stabilize the double helix?

Answer 22

The phosphate backbone is hydrophilic with charges in the aqueous solution which stabilizes the hydrophobic rxns internally.

Question 23

Is the double helix right-handed or left handed?

Answer 23

The most common form of DNA is DNA B which exists in aqueous solutions. This form is right-handed.