Mutations Flashcards
What is a mutation
Any change to an organisms DNA
Somatic mutation
Occurs in somatic cells
Not heritable - won’t affect offspring
Only the cell where the mutation occurred will be affected
Germline mutation
Occurs in gametes/ cells that make gametes
Heritable - will affect offspring
Nondisjunction
When homologous chromosomes or sister chromatids do not to separate when they are supposed to
What does nondisjunction result in?
Results in somatic cells or gametes with an incorrect number of chromosomes
Aneuploidy !!!
What is aneuploidy?
A condition where an individual has an
Incorrect number of chromosomes
(One extra/ missing)
What is polyploidy?
A condition where an individual has extra/missing SETS of chromosomes
More than 2 complete sets of chromosomes
What is trisomy?
When an individual has
3 copies of chromosomes instead of 2
(1 extra)
What is monosomy?
When an individual has 1 copy of chromosomes instead of 2
Missing 1
When looking at karyotypes,
Look whether
- male/female ?
- monosomy/ trisomy ?
XO ?
Turners Syndrome
XXY ?
Klinefelter’s Syndrome
Mitotic nondisjunction results in:
Monosomy and trisomy
Meiotic nondisjunction could happen in…
Anaphase I
or
Anaphase II
If nondisjunction occurs in anaphase I…
Homologous chromosomes do not separate
Will result in
2 trisomy and 2 monosomy 😓
If nondisjunction occurs in anaphase II…
Sister chromatids do not separate
Result in
2 normal, 1 trisomy, 1 monosomy ☹️
What is karyotyping?
Process of
analyzing the chromosomes of an individual
Can help to detect aneuploidy in humans
Karyogram
The final image of chromosomes which have been stained, photographed and sorted into their pairs
What are mutagens?
Physical/ chemical factors that increase the rate of mutation
The severity of a mutation depends on…
the overall change to the amino acid sequence
Severities of mutations
Silent mutation
Missense mutation
Nonsense mutation
Silent mutation
Cat -> Kat
No overall effect on amino acid sequence
Mutated codon still codes for same amino acid
Missense mutation
Cat -> hat
Affected codon now codes for a different amino acid.
Substitution mutation or frameshift mutation could cause this!
- Severity varies
Point missense mutations vs frameshift missense mutations
Point missense mutations
Less serious - only 1 amino acid changed
Frameshift missense mutations
More serious - many amino acids changed
Significant changes to primary structure…
Alters the secondary and tertiary structures of the protein
Change its function or make it non-functional
Nonsense mutation
‘I have a cat named’
Results in formation of Stop codon before end of gene
Shorten the amino acid chain - Could make it non-functional
If mutation occurs in the intron sequences..
Won’t affect the gene because introns are removed before translation
