L21- DNA/ chromosomal mutations Flashcards
mutagenesis
the process of mutation generation
a mutation is
a change of the nucleotide sequence, which can either have no affect on protein structure, or can render a protein changed
mutations arise
spontaenously due to mutagens
spontaneous mutations e.g.
deamination mutations
example of deamination
changes Cytosine to Uracil
e.g. can change 5-methylcytosine to thymine
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types of mutagens
exogenous
endogenous
endogennous
DNA replication defects
exogenous
- ionsing radiation
- free radical
- mutagenic chemicals e.g. nitrites
- anti cancer agents
Defective or error prone DNA repair leads to
mutation
mutations may or may not
cause phenotypic cahnge
mutations can be
good or bad
- source of genomic variation
- driving force of evolution
- may cause disease
in transcription …
- DNA is read ……..
- mRNA is synthesised ……
- DNA is read 3’ to 5’
- mRNA is synthesised 5’ to 3’
In translation….
- mRNA is read…….
- polypeptide synthesis……
- mRNA is read 5’ to 3’
- polypeptide synthesis N to C
types of mutations
small scale (micro)
large scale (macro)
small scale mutations (3)
- substitution
- deletion
- insertion
large scale mutations (macro)
- abnormal number of chromosomes
- structural abnormalities
Abnormal number of chromosomes e.g.
- aneuploidy
- polypoloidy
structural abnormalities (4)
- deletions
- duplication
- inversion
- translocation
a transposable element (transposome)
is a DNA sequence that can change position within a genome- creating or reversing mutations
transposable elements are what sort of source of mutagenesis
endogenous
DNA sequences of transposable elements
- supernumerary (many copies)
- specific
- always contain within other DNA molecule
- moves as a discrete unit
- moves to random sites
transposable elements insertionally
inactivate genes or change gene expression
TEs can insert (jump into) a gene to
inactivate it
TE can jump out of a gene to
reactivate it
TE and the size of the gene
The bigger the gene the more likely it will be inactivated
e.g. Hb gene very small- unlikely
TE can also jump into
regulatory regions- affecting DNA expression