Nucleic Acids

Question 1

What are nucleic acids? What are the nucleotides connected by?

Answer 1

Linear polymers made by connecting nucleotides via phosphodiester bonds (5’OH of one group + 3’OH of another group)

Question 2

Draw the pentose sugars for RNA (ribose) and DNA (deoxyribose) - B furanose form

Answer 2

refer to notes

Question 3

Draw cytosine

Answer 3

refer to notes

Question 4

Draw thymine

Answer 4

refer to notes

Question 5

Draw uracil

Answer 5

refer to notes

Question 6

Draw adenine

Answer 6

refer to notes

Question 7

Draw guanine

Answer 7

refer to notes

Question 8

What do tautomeric shifts do?

Answer 8

shift the H atom and double bond

Question 9

Enol form

Answer 9

everything is the same except -OH instead of =O

Question 10

Keto form

Answer 10

regular structure

Question 11

Imino form

Answer 11

everything is the same except =NH instead of -NH2

Question 12

Amino form

Answer 12

regular structure

Question 13

What is a nucleoside composed of?

Answer 13

base and sugar

Question 14

What is a nucleotide composed of?

Answer 14

base and sugar and phosphate

Question 15

Why is DNA more resistant than RNA to alkene hydrolysis?

Answer 15

Because the 2’OH group of RNA acts as a nucleophile in an intramolecular disp. breaking the phosphate bond

Question 16

Chargaffs

Answer 16

%A = %T and %G=%C [A+G] = [C + T]

Question 17

Double helix features

Answer 17

• right handed
• bases are hydrophobic (inside) and sugar phosphate backbone is hydrophilic (outside) = hydrophilic
• perp to axis
• 2 strands are antiparallel
• bp are 3.4 A apart
• comp bp are held together by H bonds

Question 18

What links the base to the pentose in nucleotides?

Answer 18

Glycosidic bond

Question 19

Calculating net charge on a nucleotide - both ends OH groups

Answer 19

(-1 x all bp) - 1

Question 20

Calculating net charge on a nucleotide - one end P one end OH

Answer 20

(-1 x all bp) +1

Question 21

Calculating net charge on a nucleotide - both ends P groups

Answer 21

(-1 x all bp) +three