Nucleic Acids topic 2.6

Question 1

Nucleotides

Answer 1

The monomer of a nucleic acid is called a nucleotide

Question 2

Each nucleotide consists of three basic components:

Answer 2

• A pentose sugar
• A phosphate group
• A nitrogenous base

Question 3

Each nucleotide possesses one of five different nitrogenous bases

Answer 3

Adenine, Guanine, Cytosine, Thymine or Uracil

T is present in DNA, whereas U is present in RNA

Question 4

Polynucleotide Formation

Answer 4

Nucleotides are linked together into a single strand via condensation reactions
(between a 5’-phosphate and a 3’-hydroxyl group of adjacent nucleotides)

This polynucleotide arrangement results in the formation of a sugar-phosphate
backbone that is covalently linked together by phosphodiester bonds

Question 5

DNA Structure

Answer 5

Two complementary strands line up in opposite directions (anti-parallel) with the
bases facing inwards and connected by hydrogen bonds (G ≡ C and A = T)

The double stranded molecule then twists in order to adopt a more stable energy
configuration – a double helix

Question 6

RNA Structure

Answer 6

The polynucleotide chain remains single stranded, but may fold upon itself to
form double stranded motifs (e.g. the cloverleaf shape of a tRNA molecule)

Question 7

DNA versus RNA

Answer 7

DNA and RNA are both polymers of nucleotides,
however they differ in a few key structural aspects

Question 8

Watson and Crick

Answer 8

The structure of DNA was elucidated by Watson and Crick in 1953

Using data from previous scientific experiments (plus trial and error),
Watson and Crick developed a DNA model that demonstrated:
* A double helix structure composed of antiparallel DNA strands
* Internally facing bases with complementary pairing (A=T, G≡C)