Mutations Flashcards
define mutation
the changing of a gene that results ina variant form that is permenant
define mutagen
any environmental agent that causes a mutation
eg. chemical, biological, physical
What causes a mutation?
- can occur spontaneously
- can be caused by a mutagens
Examples of chemical mutagen agents
exposure to:
* tar
* benzene
* asbestos
Examples of biological mutagen agents
- viruses
- bacteria
- fungi
Examples of physical mutagen agents
high-energy ionising radiation:
* UV light
* x-rays
* gamma rays
What are the 2 different types of mutations?
- point mutations
- chromosomal mutations
What does a point mutation occur with?
a single base pair
What are the 3 types of point mutations?
- point substitution
- point insertion
- point deletion
What happens in a point substitution?
one base is subsituted to another base
the nucleotide is subsituted
What happens in a point insertion?
One base is inserted into the sequence
* FRAMESHIFT occurs: all following bases shift over/are affected
What happens in a point deletion?
One base is deleted from the sequence
* FRAMESHIFT occurs: all following bases shift over/are affected
What is an example of a chromosomal disorder?
trisomy 21
What are the 4 types of chromosomal mutations?
- chromosome deletion
- chromosome duplication
- chromosome inversion
- chromosome translocation
What happens in a chromosome deletion?
a section of the chromosome breaks off and disappears
What happens in chromosome duplication?
a section of the chromosome is copied and added on
What happens in a chromosome inversion?
a section of the chromosome is detached, rotated 180° and reattached
What happens in a chromosome translocation?
a section detaches from one chromosome and reattaches to a different chromosome
What are the 4 consequences of point mutations?
- nonsense mutation
- missense mutation
- silent mutation
- frameshift
What happens in a nonsense mutation?
what happens, effects on resultant polypeptide, effects on phenotype
a triplet codon is changed to a stop codon
* resultant polypeptide is cut short
* MAJOR change to phenotype
What happens in a missense mutation?
what happens, effects on resultant polypeptide, effects on phenotype
a triplet codon is change to code for a different amino acid
* resultant polypeptide is LESS functional
* MINOR change to phenotype
What happens in a silent mutation?
what happens, effects on resultant polypeptide, effects on phenotype
a triplet codon is changed but codes for the same amino acid
* resultant polypeptide is unchanged
* NO change to phenotype
What happens in a Frameshift mutation?
what happens, effects on resultant polypeptide, effects on phenotype
everything shifts over
* resultant polypeptide’s amino acid sequence completely changes
* MAJOR change to phenotype
can only occur in insertion or deletion
What are the consequences of chemical mutations?
(2 possible effects)
- could affect phenotype
- likely to lead to amino acid sequence change in resultant polypeptide
Where does a somatic mutation occur?
in a NON-SEX CELL
What are the effects of a somatic mutation
- can’t be passed on to offspring
- can be passed on in mitotic cell division
- affects a localised part of the organism
Where does a germline mutation occcur?
in a cell that will BECOME a SEX CELL
What are the effects of a germline mutation?
- will be passed down to offspring (and will be in all cells of the offspring) - can potentially affect the whole organism of the offspring
- is a new allele in the population
