Unit 1.6 Mutations Flashcards
What are mutations?
Random changes in the DNA sequence of an organism that can result in no protein or an altered protein being synthesised. This is because the sequence of bases in the genes of an organism determines the order in which the amino acids in the protein’s structure.
If the order of amino acids is changed by a mutation this can cause a change in the shape of the protein and hence cause a change in the function of the protein.
Can we increase the rate at which mutations occur and if so explain your answer?
Yes we can by the use of what is called mutagenic agents including chemical agents and radiation.
Name the two types of mutations? (generalised)
- Single gene mutations
- Chromosome structure mutations
What occurs in a single gene mutation?
A single nucleotide in a gene is altered
What are the three types of single gene mutations?
- Substitutions
- Insertions
- Deletions
What occurs within a single gene substitution mutation?
A single nucleotide within the gene is replaced with a different nucleotide
- substitution mutations usually only have effects on one amino acid in the polypeptide and for this reason will usually only have a minor effect on the protein structure and the protein should still function.
There are two results of a substitution:
*missense - changes one amino acid and so usually results in a minor change in the protein structure
*nonsense mutations occur when only part of the protein is produced, this occurs when a substitution creates a premature stop codon and the protein produced is much shorter than intended and so in most cases will be unable to fulfill its function.
What occurs within a single gene insertion mutation?
A single nucleotide is added into the gene
What occurs within a single gene deletion mutation?
A single nucleotide will be removed from the gene.
What is a splice site mutation?
splice site mutations occur when either a substitution, insertion, or deletion mutation occur at the splice site of the Gene, this means that some introns are not removed from the primary transcript mRNA.
The introns that are left in the mature mRNA transcript as a result of a splice site mutation will then be translated and the protein will then have extra amino acids which will alter the sequence and therefore the function of the protein.
What type of mutation can occur exclusively as a result of an insertion or deletion mutation?
A frame-shift mutation In which all codons after the point of mutation will be changed as the extra or loss of a nucleotide will change the bases in each codon after this point and therefore each codon after this point will be different. This can majorly impact the shape and function of the protein produced and in many cases the protein that is produced will not be functional.
What are the different types of mutations that can occur as a result of chromosome structure mutations?
- Translocation mutations
- Inversion mutations
- deletion mutations
- duplication mutations
What happens during a translocation mutation?
a section of a chromosome that is not the original chromosome’s homologous partner will be added to the original chromosome.
What happens during an Inversion mutation?
a section of the chromosome is reversed, a segment of the chromosome breaks in two places and turns around 180 degrees before joining up again. In this way the normal sequence of genes is reversed
Which type of mutation is more deadly, single gene or chromosome structure? Explain your answer?
Chromosome structure mutations are more deadly in more cases as they cause substantial changes to the sequence of genes on a chromosome and the chromosome’s structure or even the number of chromosomes, these substantial changes to the genome of an organism are in far more cases fatal than the change of a single nucleotide within a particular gene.
What happens during a deletion mutation (chromosome structure)
A section of the chromosome is removed and genes are deleted from the chromosome, deletion mutations have a major effect on the organism as the organism will no longer be able to produce certain types of proteins.
