20.1 Gene Mutations Flashcards
What is a mutation
Any change to the quantity or the structure of the DNA of an organism
What is a gene mutation
Any change to one or more nucleotide bases, or any rearrangement of the bases, in DNA
What are the types of gene mutation
- Substitution of bases
- Deletion of bases
- Addition of bases
- Duplication of bases
- Inversion of bases
- Translocation of bases
What occurs when substitution takes place
A nucleotide in a section of a DNA molecule is replaced by another nucleotide that has a different base
What are the 3 possible consequences of substitution
- The formation of one of three stop codons that mark the end of a polypeptide chain. This stops polypeptide synthesis
- The formation of a codon for a different amino acid, meaning the resultant polypeptide would differ by 1 amino acid
- The formation of a different codon but one that produces a codon for the same amino acid as before. This is because the genetic code is degenerate and so most amino acids have multiple codons
What occurs when deletion takes places
A nucleotide in a section of DNA is lost. This causes a frame shift to the LEFT
What occurs when addition takes place
An extra base becomes inserted in the sequence. THis causes a frame shift RIGHT
What occurs when duplication takes place
One or more bases are repeated. This causes a frame shift RIGHT
What occurs when inversion takes place
A group of bases become separated from the DNA sequence and rejoin at the same position but back to front.
What occurs when translocation takes place
A group of bases become separated from the DNA sequence on one chromosome and become inserted into the DNA sequence of a different chromosome.
What can cause mutations
- High energy ionising radiation - e.g. Alpha and BEta particles and UV/X-ray
- Chemicals like nitrogen dioxide and those found in cigarettes
