Chemistry of nucleic acids

Question 1

What is the chemical makeup of DNA?

Answer 1

A nitrogenous base (1 of 4)
A phosphate group
A ribose sugar

Question 2

Glycosidic bonds in DNA

Answer 2

Join the nitrogenous base to the ribose sugar

Question 3

Ribose sugar

Answer 3

Puckered ring. 5 carbons and 1 oxygen in the ring - 6th carbon is on the 5th carbon in the ring.

Question 4

2 types of phosphate

Answer 4

Purine
Pyrimidine

Question 5

Purine

Answer 5

Adenine (NH2 group)
Guanine (NH2 and =O)

Question 6

Pyrimidine

Answer 6

Cytosine (NH2)
Thymine (CH3 and =O)
Uracil - RNA only - (=O)

Question 7

Where does the phosphate join on the ribose? How?

Answer 7

Carbon 5 by an ester link (5’)

Question 8

Difference between nucleoside and nucleotide?

Answer 8

Nucleotide has a phosphate group - the nucleoside also has an extra O2 compared to deoxynucleotide.

Question 9

What is dAMP?

Answer 9

Deoxyadenosine monophosphate. It is a monomer used in DNA.

Question 10

How do the monomers in DNA link together?

Answer 10

Through 3’ - 5’ phosphodiester bonds. This forms the phosphodiester backbone of the DNA.

Question 11

Sequence hypothesis

Answer 11

The amino acid sequence of a protein is determined by the sequence of nucleotides within the DNA.

Question 12

DNA oligonucleotide

Answer 12

Short strands of DNA.
Often used as a primer for PCRs.

Question 13

Watson and Crick

Answer 13

Model of the structure of DNA (1953)

Question 14

What is the most dominant form of DNA?

Answer 14

B-form. Other forms include A and Z form DNA.

Question 15

How is DNA packaged in humans?

Answer 15

Wrapped around histone proteins, 4 proteins in the octamer, DNA is wrapped around twice.

Question 16

DNA gyrase

Answer 16

Type of topoisomerase which interchanges between relaxed and supercoiled DNA.

Question 17

Circular DNA

Answer 17

Bigger - bacterial genomes
Smaller - mitochondrial, choloroplasts etc.
Can be supercoiled or relaxed.

Question 18

Denaturation

Answer 18

When the DNA splits into two strands rather than being in a typical helical structure. This happens when heated.

Question 19

Hybridisation

Answer 19

When two strands of DNA rejoin after being separated in denaturation.

Question 20

How do you distinguish between single and double-strand DNA?

Answer 20

By the absorbance of UV light.
Single: more absorbant
Double: less absorbant

Question 21

How would you keep DNA denaturated?

Answer 21

If you cool rapidly. Will re-anneal/ perform hybridisation if cooled slowly.