Nucleic Acids

Question 1

Freidrich Miescher

Answer 1

first isolated DNA in 1868 and called it nuclein

Question 2

what are nucleic acids

Answer 2

biochemical macromolecules that encode genetic information

Question 3

primary structure of nucleic acids

Answer 3

• linear polymers made by connecting nucleotides via phosphodiester bonds
• repeating unit is the nucleotide
• sugars are linked together by the phosphates and form the sugar phosphate backbone

Question 4

what is the charge of phosphates

Answer 4

negative

Question 5

nucleotide

Answer 5

consists of a sugar, a N base and a phosphate group

Question 6

pentose sugars found in nucleic acids

Answer 6

in RNA: D-ribose
in DNA: D-2-deoxyribose (OH of C2 is replaced with an H)
- both sugars occur in beta furanose form

Question 7

N bases

Answer 7

derivatives of pyrimidines and purines

Question 8

pyrimidines

Answer 8

single ring structures
- cytosine and thymine (replaced by uracil in RNA)

Question 9

Tautomers

Answer 9

isomers that differ by the shift of a H atom and a double bond

Question 10

Tautomeric forms of cytosine

Answer 10

• the OH group undergoes keto/enol tautomerism
• the NH2 group undergoes amino/imino tautomerism

Question 11

purines

Answer 11

• the purine ring is a fused bicyclic heterocyclic
• adenine and guanine

Question 12

nucleoside

Answer 12

base + sugar
- a base is joined to the sugar through a glycosidic bond
- sometimes called a glycosylic bond to designate C-N linkages
- N1 of pyrimidines and N9 of purines

Question 13

linking purines and pyrimidine bases to sugars

Answer 13

• linked through glycosylic bonds
• the NH at position 9 of purines and the NH at position 1 of pyrimidines link to the anomeric carbon of the pentose sugar
• releases H2O

Question 14

nucleotides

Answer 14

base + sugar + phosphate
- just phosphoester at this point not diester

Question 15

phosphodiester linkages

Answer 15

• link the nucleotide units of DNA and RNA
• phosphate group bridges between the 5’ OH of one nucleotide with the 3’ of another forming a linkage
• each linear strand has a specific 5’ and 3’ ends which lack a nucleotide
• the phosphate group is completely ionized and negatively charges at pH 7

Question 16

stability of RNA and DNA

Answer 16

RNA is rapidly hydrolyzed under alkaline conditions
DNA is much more stable since it lacks the 2’ hydroxyl group (which acts as a nucleophile and breaks phosphodiester linkages)