MUTATIONS U1 Flashcards
State the definition of a mutation
Mutations are changes in DNA that can result in no protein or altered protein being synthesised.
Describe single gene mutation, naming the 3 types of gene mutation
Single gene mutations involve the alteration of a DNA nucleotide sequence as a result of:
the substitution of nucleotides. (replacing 1 nucleotide with another);
insertion of nucleotides;
deletion of nucleotides.
Name and describe 3 mutations caused by a substitution of nucleotides
The 3 types of mutations caused by substitutions are:
Missense mutations – result in one amino acid being changed for another. This may result in a non-functional protein or may have little effect on the protein depending on the amino acid that has been changed. Example Sickle cell disease.
Nonsense mutations result in premature stop codon being produced which results in a shorter protein. Example Duchenne Muscular dystrophy.
Splice site mutations result in some introns being retained and/or some exons not being included in the mature transcript. Example beta thalassemia.
Describe a frame shift mutation
The effect of an insertion or deletion of a nucleotide results in frame shift mutations.
Examples:
Cystic fibrosis – Deletion
Tay-Sachs disease - Insertion
Frame shift mutations cause all of the codons and all of the amino acids after the mutation to be changed.
This has a major effect on the structure of the protein produced.
The 4 types of chromosome mutation are?
Duplication, Deletion, Inversion, Translocation
Duplication
A section of a chromosome is added from its homologous partner.
(You inherit 2 copies of each chromosome, one from each biological parent. These chromosomes are homologous partners. For example, in this type of mutation part of chromosome 1 is added to the other chromosome 1).
Deletion
A section of the chromosome is removed.
Inversion?
A section chromosome is reversed.
Translocation?
A section of a chromosome is added to a chromosome, not its homologous partner.
State the importance of mutations and gene duplication in evolution
Duplication allows potential beneficial mutations to occur in duplicated gene whilst the original gene can still be expressed to produce its protein.
For example – the chromosome still has the original gene and so produces the correct protein. However, the duplicated mutation may also produce another protein /characteristic that gives the organism a select advantage over others without any negative consequences.
