mutations - gene & chromosome Flashcards
what is a mutation?
Permanent changes to the genetic material of an organism
What is a gene mutation?
The alteration of the base sequence by altering a base
Why might an amino acid sequence stay the same after a mutation?
DNA code is degenerate - multiple codons code for the same amino acid
When is a gene mutation likely to happen?
During S-phase as DNA replication is occurring
When do mutations happen?
Randomly/spontaneously
W
Randomly/spontaneously
How can the likelihood of mutations occurring be increased?
Increased by mutagenic agents - such as alcohol, radiation, tobacco
What happens if the amino acid sequence changes?
- tertiary structure changes as bonds change
- results in non-functioning protein
- if enzyme, will no longer be complementary to substrate
What is an insertion/addition mutation?
- one or more bases is added
- all codons are altered (frameshift)
- could code for different amino acid
What are the types of gene mutations?
Insertion, deletion, substitution, duplication, inversion, translocation
What is a deletion mutation?
- deletion of one or more bases
- causes frame shift as all codons affected
- result in different polypeptide
What is a substitution mutation?
When one or more bases are swapped for another
- number of bases stay the same, no framehshift
- only one codon changes
What is an inversion mutation?
When the sequence of bases is reversed
Could cause different amino acid to be coded for
What is a translocation mutation?
- when a section of bases detaches and reattaches onto a different chromosome
- significant impact on gene expression and can affect phenotype
What is a duplication mutation?
- when one or more bases are repeated
- can cause frameshift and genetic diseases
what is a frameshift mutation?
- changes number of bases in DNA code, shifts all codons, DNA code is transcribed differently
What are chromosome mutations?
Mutations in the number of chromosomes can arise spontaneously by chromosome non-disjunction during meiosis
When do chromosome mutations occur?
Occurs during metaphase 1 and anaphase 1
What is non-disjunction?
when chromosomes or chromatids don’t split equally during anaphase
What are two forms of non-disjunction?
aneuploidy and polyploidy
What is polyploidy?
