Q5: Gene mutations and their effects Flashcards
Mutation
Any change to the quantity or the structure of the DNA of an organism.
Gene mutation
Any change to one or more of the nucleotide bases, or any rearrangement of the bases in DNA.
Types of mutations
6
substitution deletion addition duplication inversion translocation
Substitution of bases
A mutation in which a nucleotide in a section of a DNA molecules is replaced by another nucleotide that has a different base.
Consequences of a substitution mutation
3
- Formation of a stop codon which is premature
- Formation of a different codon for a different amino acid
- Formation of a different which produces the same amino acid
Deletion of base(s)
The loss of a single nucleotide base from a DNA sequence
Deletion of bases frame shift direction
to the left
Addition of bases
An extra base is inserted in the DNA sequence
Addition of of bases frame shift direction
to the right
Duplication of bases
One or more bases are repeated
Duplication of bases frame shift direction
to the right
Inversion of bases
A group of bases become separated from the DNA sequence and rejoin at the same position but in the inverse order
Translocation of bases
A group of bases becomes separated from the DNA sequence of one chromosome and become inserted into the DNA sequence of a different chromosome
Gene mutations can arise … during DNA replication
spontaneously
Spontaneous mutations
Permanent changes in DNA that occur without any outside influence.
Despite being random occurrences…
mutations occur with a predictable frequency
Mutagenic agents/ mutagens
increase the basic mutation rate
Mutagenic agents/ mutagens
2 types
chemicals
high energy ionising radiation
High energy ionising radiation
as a mutagen
Alpha and beta particles and short length radiation can disrupt the structure of DNA.
Short length radiation which can be a mutagen
x-rays and UV light
Chemicals
as mutagens
Directly alter the structure of DNA or interfere with transcription.
Example of chemical mutagen
nitrogen dioxide
Benefit of mutations
produce genetic diversity
Disadvantage of mutations
2
almost always harmful
produce an organism less well suited to its environment