Classifying mutations Flashcards
What are 3 ways to classify mutations?
At the DNA level, based on the change to the polypeptide, based on the effect on the function of the gene product
What is a base substitution?
One base is replaced by a different base
What are the two types of base substitutions?
Transitions and transversions
What is a transition mutation?
A purine gets replaced by another purine, or a pyrimidine gets replaced by another pyrimidine
What is a transversion mutation?
A purine gets replaced by a pyrimidine, or a pyrimidine gets replaced by a purine
What is the problem with classifying mutations based on their effect on the polypeptide?
Only applicable to mutations in the coding region of a gene
What is a silent mutation?
Causes no change in the encoded amino acid
What is a missense mutation?
Causes a different amino acid to be encoded
What are the two types of missense mutations?
Conservative: new amino acid has similar chemical properties
Non-conservative: new amino acid has different chemical properties
What is a nonsense mutation?
Causes an amino acid-encoding codon to be changed to a stop codon
What is a frameshift? What type of mutation causes these?
Causes a change in the reading frame. Caused by indels or larger insertions or deletions
What is an inversion?
A fragment gets cut out and its orientation gets reversed before getting ligated back in
What is a reciprocal translocation?
Two fragments from non-homologous chromosomes switch places
What is a non-reciprocal translocation?
A fragment from one chromosome replaces a fragment on a non-homologous chromosome, and the fragment from that other chromosome gets deleted
