The Structure of DNA – HSC Biology

  • DNA replication using the Watson and Crick DNA model, including nucleotide composition, pairing and bonding


James Watson is a American biologist and Francis Crick is an English physicist, they are credited with discovering the structure of DNA.

DNA contains the genetic information used as a blue print to create people. If you had someone’s genome (all of their DNA), you would be able to make a clone of them since you have all the genetic information which codes for all of their features.

As seen below, DNA contains bases – Adenine (A) and thymine (T) bind together and guanine (G) and cytosine (C) bind together. Remember this as AT – Gold Coast. This means if we have one of the two strands of DNA, we are able to construct the second strand since this just contains the opposite basses. For example one strand would be ATG, the other would have to be TAC.

Unravelling the double helix | Stories |
From your genome

This idea will be revisited for DNA replication.

These bases are connected by a sugar phosphate backbone, as seen above as the blue ribbon. This twirls around in opposite direction forming the double stranded DNA.


AT – Gold Coast


Question 1.

Explain the structure of DNA and the three molecules that it is composed of. [2 marks]

Question 2.

You have been told that a DNA sequence of one strand of DNA is 5′ – ATGTGCATCG – 3′, what is the sequence of the complimentary strand. [2 marks]


Question 1.

sugar, phosphate, base

Question 2.

3′ – TACACGTAGC – 5′

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