Nucleic Acids

Question 1

What are the two nucleic acids?

Answer 1

Deoxyribonucleic acid or ribonucleic acids

Question 2

What is the difference between a nucleoside and a nucleotide?

Answer 2

Nucleoside: Sugar + Nitrogenous base

Nucleotide: Sugar + Nitrogenous base + Phosphate

Question 3

What is the difference between deoxyribose and ribose?

Answer 3

Deoxyribose: lacks an OH group on 2’-Carbon

Ribose: contains an OH group on 2’-Carbon

Question 4

What is the difference in numbering on pentose sugar and nitrogenous base?

Answer 4

Sugar: uses primed numbering
Nitrogenous base: normal numbering

Question 5

What are purines and pyrimidines?

Answer 5

Pyrimidines: single ringed (cytosine, thymine)

Purines: double ringed (Guanine, Adenine)

Question 6

What is the difference in base pairing between CG and AT/AU?

Answer 6

C-G: three hydrogen bonds (harder to break)

AT/AU: two hydrogen bonds (easier to break)

Question 7

What is the terminology to denote phosphate groups on nucleotides?

Answer 7

“nucleoside X-phosphate”

X = mono, di, tri

Question 8

What is the sugar phosphate backbone?

Answer 8

Backbone of DNA strand forming a polymer of alternating pentoses on 3’-Carbon and phosphates on 5’-Carbon

Question 9

What is a phosphodiester bond?

Answer 9

An ester bond between an oxygen on a phosphate to the 5’ carbon of a pentose sugar in DNA

Question 10

What did Linus Pauling do?

Answer 10

Devised 3D ball and stick model to deduce structure of folded protein

Question 11

What did Rosalind Franklin and Maurice Wilkins do?

Answer 11

Subjected crystallized DNA to X-ray beam which determined diffraction pattern that could be mathematically interpreted to provide helical structure.

Question 12

What did Erwin Chargaff do?

Answer 12

1. Extracted Chromosomal DNA
2. Added protease to remove protein
3. Acid treated DNA to hydrolyze bases from DNA strands
4. Subjected isolated bases to paper chromatography
5. Determined amount of each by light spectroscopy

Discovered % A = % T, and % G = % C

Question 13

What did James Watson and Francis Crick do?

Answer 13

Built models based on scientific clues of DNA, including parallel backbones with matching bases, but revised model by aligning A’s to T’s, G’s to C’s as per Chargaff’s rule.

Question 14

What is the difference in RNA and DNA?

Answer 14

RNA: uses ribonucleotides, uses Uracil, single stranded and forms unique shape based on base interactions

DNA: uses deoxyribonucleotides, uses Thymine, 2 hydrogen bonded single strands of polynucleotides to form double helix

Question 15

What is the vertical length of a single turn of the helix? How many base pairs are there per turn? What is the degree of rotation of a bp relative to the previous one?

Answer 15

3.4 nm, 10 base pairs, 36º

Question 16

What is the major and minor groove?

Answer 16

Areas of greater exposure (major) and lesser exposure (minor) of nitrogenous bases as a result of geometry of stacking base pairs in a DNA molecule.