Lecture 10: DNA structure

Question 1

What kind of bonds form a polynucleotide = nucleic acid = DNA

Answer 1

phosphodiester
bonds

Question 2

How does a phosphodiester
bond form

Answer 2

The hydroxyl group (OH) on the 3rd carbon of one
nucleotide reacts with the phosphate group
attached to the 5th carbon on another nucleotide.

Question 3

What is Chargaffs rule

Answer 3

A = T
G = C

Question 4

Explain the Watson-Crick model fo DNA

Answer 4

DNA has a double stranded helical structure

The sugar phosphate backbone is on the outside

The bases are on the inside

Stabilised by hydrogen bonds

The two polynucleotide strands are oriented in opposite
directions

Question 5

What kind of replication model does DNA undergo

Answer 5

Semi-conservative mode, this means that each DNA strand of the double helix is used as a template strand for
the synthesis of two new strands.

Question 6

In which ‘direction’ does a DNA chain grow when being synthesised?

Answer 6

5’ to 3’ direction

Question 7

Which nucleotide component(s) are located on the inside of the DNA
helix and which are located on the outside of the DNA helix?

Answer 7

Outside:
- Sugar phosphate

Inside:
- Bases

Question 8

How many polynucleotide chains make up a DNA molecule and how
are these organised in relation to each other?

Answer 8

2 antiparallel chains that form in a double helix structure