7.2: types of mutations Flashcards
how to differentiate mutations
- origin of mutation
- amount of genetic material changed
- effect of mutation on DNA
- effect of mutation on phenotype
- heritability of mutation
origin/cause of mutation
spontaneous vs induced:
- spontaneous: occurs due to an error in a natural process such as DNA replication
- induced: occurs as a result of an environmental agent
amount of genetic material changed
point vs frameshift
- point: changes to a single base pair
- frameshift: affects single gene/sequence of genes, can be due to point or chromosomal mutation
effect of mutation on DNA
can be substitution, insertion, or deletion of nucleotide bases
- may result in change in one amino acid
effect of mutation on phenotype
silent vs variation
- silent: no change in phenotype
- variation: is change in phenotype, can be harmful, neutral, or beneficial
heritability of mutation
determines whether or not it will be passed down
point mutation
single nucleotide variation
- can cause significant change if occurring within exon, or an intron which affects gene expression
base substitution
occurs when one base is replaced by a different base
- may result in different amino acid, which changes function of protein
- if resulting in phenotypic effect, called missense mutation
frameshift mutation
occurs when the ‘reading frame’ shifts, creating a whole sequence of incorrect amino acids to produce a non-functional protein
- can be from insertions and deletions
- can be caused by point/chromosomal mutations
nonsense mutations
changes an amino acid to a stop codon, cuts protein short
- results in non-functional protein, major phenotypic effect
missense mnutations
results in amino acid change
- resulting change in phenotype determined whether or not replacement amino acid is same as the original
silent mutations
does not result in change in amino acid
- due to redundancy of genetic code the change is in
neutral mutations
amino acid is same type as original
- nothing really changes, same amino acid = same protein structure
chromosomal mutation
overall structure changed, or entire number of chromosomes in cell changed
four types of mutations that alter structure
deletions, insertions, inversions, translocations
chromosomal deletion
section is removed, not replaced
- reduces number of genes in chromosome
- usually result of high exposure to high heat, viruses, or radiation
chromosomal insertion/suplication
portion is duplicated, inserted
- increases number of genes on chromosome
- effect and whether it affects phenotype depends on size, location, number of repeats
- copy number variations: when repeat copies is above a certain threshold, results in diseases like huntington’s chorea or fragile X syndrome
chromosomal inversion
DNA removed, flipped 180, reinserted
- bases in reverse order
- can cause disease like haemophilia A, which is X-linked
chromosomal translocation
section moved from one chromosome to a non-homologous one
- may lead to gene fusion when translocated region joins two separate genes not originally joint
aneuploidy
changes in chromosome number
