1.6) Mutations

Question 1

• What is ‘missense’?

Point Mutation

Answer 1

• ‘Missense’
  ➞ a single nucleotide substitution
  ↳ which results in one amino acid codon being replaced with another.
  ➜ results in non-functional protein or may have very little effect on the protein.

(e.g. PKU)

Question 2

• What is ‘nonsense’?

Point Mutation

Answer 2

• ‘Nonsense’
  ➞ a single nucleotide substitution
  ↳ which results in one amino acid codon being replaced with a premature STOP codon
  ➜ results in a shorter protein.

(e.g. Duchenne’s Muscular Dystrophy)

Question 3

• What is ‘splice-site’?

Point Mutation

Answer 3

• Splicing
  ➞ controlled by specific nucleotide sequences
  ↳ at locations called ‘splice-sites’
• ‘Splice-site’
  ➞ mutations
  ↳ which result in some introns being retained and/or some exons not being included in the mature transcript.

Question 4

• What is ‘insertion’?

Frameshift Mutation

Answer 4

• ‘Insertion’
  ➞ of one or more DNA nucleotides
  ↳ results in the shifting of existing nucleotides
  ➜ altering DNA, RNA and amino acid sequence (and ultimately protein structure)

Question 5

• What is ‘deletion?

Frameshift Mutation

Answer 5

• ‘Deletion’
  ➞ of one or more DNA nucleotides
  ↳ results in the shifting of existing DNA base sequences
  ➜ altering DNA, RNA and amino acid sequence (and ultimatelty protein structure)

Question 6

• What is ‘deletion’?

Chromosome Mutation

Answer 6

• A section of the chromosome is removed.

➞ (conditions caused - usually lethal - since mutant is unable to code for certain essential proteins)

Question 7

• What is ‘duplication’?

Chromosome Mutation

Answer 7

• A section of the chromosome is added from its homologous partner.

➞ (Duplication - allows potential beneficial mutations to occur in a duplicated gene - whilst the original gene can still be expressed to produce protein)

Question 8

• What is ‘translocation’?

Answer 8

• A section of the chromosome is added to another chromosome, not its homologous partner.

Question 9

• What is ‘inversion’?

ChromosomeMutation

Answer 9

• A section of the chromosome is reversed.

Question 10

• What is the recap between Point mutation and Frameshift mutation?

Answer 10

• POINT MUTATION:
  ➞ only affects one amino acid
  ↳ (e.g. substitution)
• FRAMESHIFT MUTATION:
  ➞ have a knock-on effect on other amino acids
  ↳ (e.g. insertion and deletion)
  ➜ All the amino acids after the mutation will change and these frameshift mutations have a major effect on protein structure.