1.4

Question 1

What are single gene mutations

Answer 1

Single gene mutations involve the alteration of a DNA sequence as a result of the:
substitution
insertion
or deletion of nucleotides

Question 2

What do Nucleotide Substitutions include

Answer 2

Missense (replacing one amino acid codon with another which may result in a non-functional protein or have little effect on it - sickle cell disease)
Nonsense (replacing an amino acid codon with a stop codon which results in a shorter protein - DMD)
Splice-site mutations (some introns are retained or some exons are not included in mature transcript which creates a protein which doesn’t function properly - Thalassemia)

Question 3

What are Frameshift Mutations

Answer 3

Frameshift mutations lead to major changes because it causes a large portion of the genes DNA to be misread.
Every amino acid after the mutation is affected so the protein is usually non-functional.
Nucleotide Insertions & Deletions result in Frameshift Mutations

Question 4

What are Chromosome Structure Mutations

Answer 4

Chromosome structure mutations involve a change in the sequence or number of genes on a chromosome.
Examples are:
Deletion (is where a section of a chromosome is removed - Cri du Chat)
Inversion (where a section of a chromosome is reversed - Haemophilia A)
Duplication (where a section of a chromosome is added from its homologous partner - this results in a section of genes being repeated)
Translocation (where a section of a chromosome is added to a chromosome but not its homologous partner - Chronic myeloid leukaemia)
The substantial changes in chromosome mutations often make them lethal.