Lecture 1 - Structure of DNA

Question 1

Which monomer makes up DNA?

Answer 1

Nucleotides

Question 2

What is the composition of a nucleotide?

Answer 2

A sugar - deoxyribose
A phosphate group
A base which is attached to the sugar with a β-N-glycosidic bond

Question 3

What are the two types of bases?

Answer 3

Purines have two rings (eg Adenine and Guanine)
Pyrimidines have one ring (eg Cytosine and Thymine)

Question 4

How are the nucleotides arranged in a strand of DNA?

Answer 4

Nucleotides are joined by phosphodiester bonds to form two polynucleotide strands
The strands form a double helix structure

Question 5

What are some features of the double helix?

Answer 5

Antiparallel strands
A minor groove and minor groove
Strands held together by complementary base pairing using hydrogen bonds
Number of C and G nucleotides in the DNA of an organism is the GC content

Question 6

What are the 3 types of double helix?

Answer 6

B-DNA
A-DNA
Z-DNA

Question 7

What is B-DNA?

Answer 7

The most common form of DNA
Right handed helix
10 base pairs by turn
Wide deep major groove
Narrow shallow minor groove

Question 8

What is A-DNA?

Answer 8

Rare form, only happens when there isn’t enough water around
Right handed
11 base pairs per turn
Narrow deep major groove
Wide shallow minor groove

Question 9

What is Z-DNA?

Answer 9

Found in B-DNA in certain regions
Biologically active but no clear function
Left handed
12 base pairs per turn
Flat major groove
Narrow deep minor groove

Question 10

Who discovered the double helix model of DNA?

Answer 10

Watson and Crick with data from Franklin