Learning Objectives:

By the end of this article you should be able to:

• List, and describe the major types of mutation (point, frameshift, block)
• Define the complex sounding words used to describe the genetic code (redundant, universal, triplet, codon, anti-codon)

The Genetic code:

Codon: a trinucleotide sequence (triplet of nucleotides) in an mRNA molecule that corresponds to a specific amino acid or STOP code.

The complementary sequence to a codon is called a triplet in DNA, and an anticodon in tRNA.

Match the Definition to the Fancy Word Quiz

VCAA sometimes refers to the genetic code as being degenerate, redundant and universal. But what do these terms refer to?

Reveal answers

1. Antiparallel

   The two DNA strands run alongside each other in the opposite direction (with respect to the 5' phosphate and the 3' hydroxyl group)
2. Redundant

   Multiple different DNA sequences can encode the same amino acid / protein
3. Degenerate

   A change to a DNA sequence doesn't always result in a change to the protein it encodes
4. Condensation Polymerisation

   The phosphodiester backbone of a DNA strand forms from the addition of nucleotides, resulting in the loss of water
5. Universal

   The same DNA sequence encodes for the same protein no matter what organism it is in
6. Gene

   A DNA sequence which encodes a specific protein product
7. Complementary Base Pairing

   Particular nucleotides only ever pair up with each other using hydrogen bonds. (e.g. A - T, G - C)

Mutations:

A mutation is any permanent change in DNA base sequence, structure or length.

Mutations can be spontaneous (i.e. randomly occurring likely due a mistake made during cell division) or induced (i.e. occurring because another factor broke the DNA, or cause the DNA repair mechanisms to malfunction). A factor which can induce mutations is called a mutagen.

UV Rays are example of a mutagen, which is why you should keep out of the sun!

A mutation or change to the DNA that occurs in one your body cells (more correctly known as ‘somatic cells’) may cause you harm by e.g. leading to cancer if a number of mutations accumulate, but are not inherited by your children Only mutations that occur in the gametes (egg or sperm cells) which ultimately become your offspring. can be passed down.

Types of mutations

Note: This section of material is no longer in the Unit 3 & 4 VCE Biology Study Design (2022-2026), but I’ve left it here below for students studying other curriculum.

Match the definition to the type of mutation quiz

Extra resources

Further reading on the complex DNA terms that VCAA loves to chuck in a multiple choice question

Khan Academy Genetic Code Article

Skip to the ‘Properties of the genetic code’ section

More information on the types of mutations

Nature Education: Genetic mutation

Douchy’s VCE Biology Podcast