Genetic information - MUTATIONS AND THEIR EFFECTS Flashcards
What is a mutation?
Any change to the quantity or base sequence of DNA
What is a gene mutation?
Any change to one or more nucleotide bases, or a change in the sequence of bases in DNA
What effect will a change in one or more of the bases in the DNA triplet have on the structure of a protein?
- Change in the sequence of amino acids
- Primary structure changes
- Hence all other structures of protein will change
What are the 7 different types of mutations?
- Substitution
- Deletion
- Addition
- Duplication
- Inversion
- Translocation
- Chromosome mutations
What is a substitution mutation?
When a nucleotide is replaced by another nucleotide that has a different base
What is the effect of a substitution mutation?
- The original amino acid may be replaced, changing the shape of the protein, and limiting the function (especially true of enzymes)
- Original amino acid may be replaced, but there is no effect on formation of bonds and protein will function normally
- Mutation may even lead to the same amino acid being coded for (DNA is degenerative)
What are silent mutations?
Mutations that occur but do not change the amino acid produced
What is a deletion mutation?
When a base is removed, re-ordering how the bases are read from the point of deletion (FRAMESHIFT)
What is the effect of a deletion mutation?
- Likely to result in an entirely different polypeptide sequence
- Protein is unlikely to function
What is an addition mutation?
An extra base is inserted into the sequence
What is the effect of an addition mutation?
Frameshift to the right
What is a duplication mutation?
One or more bases are repeated
What is the effect of a duplication mutation?
Frameshift to the right
What is an inversion mutation?
Group pf bases become separated from the DNA sequence and re-join at the same position but back to front
What is the effect of an inversion mutation?
Amino acid sequence is changed
What is a translocation mutation?
A group of bases becomes separated from the DNA sequence on one chromosome and is inserted onto another
What is the effect of a translocation mutation?
- Significant errors and abnormal phenotypes
- For example, certain types of cancer and infertility
What are chromosome mutations?
- Changes to the structure/number of whole chromosomes
- Due to failure to separate during meiosis
- A gamete may have one more or one fewer chromosomes
What are the causes of mutations?
- Mutations arise spontaneously during DNA replication
- However, mutation rate can be increased with exposure to mutagenic agents
Give some examples of mutagenic agents
- High energy ionising radiation: Alpha and beta particles disrupt the structure of DNA
- Certain chemicals: Alter the structure of DNA or interfere with transcription
