6.1.1(Gene Mutations)

Describe what is meant by a gene mutation

• A mutation is a change to the DNA base sequence by inserting, deleting or substituting the base

State the 2 main types of mutations that you need to know

• Point mutations

• Indel mutations

Describe what is meant by a point mutation

• A mutation in the DNA base sequence, where a nucleotide is replaced by another nucleotide

Describe what is meant by an indel mutation

• A mutation in the DNA base sequence, where a nucleotide is inserted or deleted in the DNA sequence

State the 3 main types of point mutation

• Silent

• Missense

• Non-sense

Describe what is meant by a silent mutation

• A type of point mutation which involves the change of a base triplet, where the triplet still codes for the same amino acid and so unaffected by the mutation-degenerate. Non-frameshift mutation

Describe what is meant by a missense mutation

• A change to the base triplet sequence which leads to the change in the amino acid sequence in a protein

Describe the effects of the missense mutation

• Disrupts the primary structure the amino acid and so the tertiary structure of the polypeptide is irregular and so the protein is not functional

Describe what is meant by a nonsense mutation

• A type of point mutation which alters a nucleotide in a triplet, causing the amino acid to become a terminator codon

Describe the effect of nonsense mutation

• This causes one of the amino acids to become a terminator, which causes the length of the polypeptide to be shorter and therefore not have the normal tertiary structure and therefore unable to carry out its function

Describe how indel mutations affect amino acid sequence and the protein

• They cause an irregular amino acid sequence by inserting or deleting a gene

• This causes all subsequent base triplets to be altered - frameshift

• This disrupts the primary amino acid sequence and therefore the tertiary and therefore the function on the protein

Define the term frameshift mutation

• A mutation which occurs when inserting or deleting a nucleotide base pair in a gene which results in altering of all amino acids after the mutation

Describe the benefits of genetic mutations

• Mutations are what have caused evolution of species

• Major source of genetic variation in a population increasing biodiversity

• Can increase chances of survival by being an advantageous gene mutation which is then passed onto offspring

Describe the dangers of mutations

• Can lead to harmful diseases and if in some areas of cells can lead to development of tumours

• Mutations which occur in genes that control cell division results in irregular growth taking place and the development of a tumour occurs - uncontrolled cell division

State and give examples what increases the rate of mutation

• Mutagens:

  • Radiation

  • Some organic chemicals