U1:KA6 - Mutations Flashcards
What is a mutation?
A mutation is a random change to genetic material they do not happen very frequently
What can mutations result in?
They can result in no protein or an altered protein being synthesised
What is a single gene mutation?
A mutation which only affects a few bases
What is a chromosome structure mutation?
A mutation which can affect the structure of one or more chromosomes
What do single gene mutations involve?
They involve a change in one of the base pairs in the DNA sequence of a single gene
What are the 3 different types of point mutations?
Substitution, insertion, deletion
What happens in a substitution mutation?
One nucleotide is substituted for another within a DNA sequence and a wrong amino acid may be inserted into a protein
What happens in an insertion mutation?
A certain number of nucleotides are inserted into a DNA sequence and all subsequent triplets are read incorrectly
What happens in a deletion mutation?
Deletion means a certain number of nucleotides are removed from the DNA sequence and all the subsequent triplets are read incorrectly
What are the 3 different effects of substitutions?
Silence, missense, nonsense
What does silence mean?
Has no effect on the protein sequence
What does missense mean?
Replacing one amino acid codon with another (non functioning protein/little effect)
What does nonsense mean?
Replacing an amino acid codon with a premature stop codon - no amino acids made an process stops (shorter protein)
What can mutations at splice sites result in?
They can result in the inclusion of an intron in a mature mRNA which should not be, and may result in a non-functional protein
What are 4 examples of mutations?
Sickle cell anaemia, cystic fibrosis, duchenne muscular dystrophy, phenylketonuria
What is sickle cell anaemia and what is it caused by?
It is caused by a single substitution mutation on the haemoglobin gene, causing changes in the shape of red blood cells, thus reduced oxygen flow in the body.
What is cystic fibrosis and what is it caused by?
It is caused by a 3 base deletion, removing a codon and causing a frame shift to occur results in thick mucus in respiratory system
What is duchenne muscular dystrophy and what is it cause by?
It is caused by several deletions within a gene, causing a frame shift mutation resulting in no dystrophin protein being made with no protein, muscles are weak and development is affected
What is phenylketonuria and what is it cause by?
It is caused by a deletion, resulting in a frame shift and earlier stop codon the resulting protein in non-functional and results in phenylalanine to build up to a toxic level, affecting brain development, treatable if caught early
What do chromosome mutations arise through?
Changes in the structure of chromosomes
When can changes in the structure of chromosomes occur?
They can occur when a chromosome breaks the cell then attempts to repair the break, but in doing so may not restore the chromosome to its original structure.
What does duplication allow?
It allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce protein
