TOPIC V MUTATIONS Flashcards
(109 cards)
What is a mutation?
Change in nucleotide sequence of DNA that may alter the function of a protien
What is the effect of a mutation?
Mutation can occur anywhere in the DNA. If it occurs WITHIN a gene, it may or may not have an impact on the encoded gene product or its expression
What do mutations outside of ‘coding’ regions affect ?
- Binding sites
- Alternative splicing (way exons are brought together)
What allows for variation?
The introns
What do alleles arise from?
Mutations
What effects can mutations in genes have?
- Prevents protein from forming e.g lack of dystrophin (muscular dystrophy)
- Reduces quantity e.g. slow blood clotting in heamohpila A
- Reduces protein efficiency e.g. sickle cell anaemia
- changes protein function e.g. extra aa’s alter function in Huntingtons disease
Are inherited mutations present in multifactorial disorders?
- They might be, they also might not..
- They are responsible for single gene disorders though like CF
Are non inherited mutations present in multifactorial disorders?
YES! They CONTRIBUTE to multifactorial disorders such as cancer, heart disease, diabetes, Alzheimers, predisposition diseases
- Are also cumulative (mutations cumulate with age)
- Also UV
What are the major classes of mutation?
- Point Mutations
- Large scale mutations
- Trinucleotide repeat expansion
What are the types of point mutations?
- Base substitutions ( missense, nonsense, silent)
- Single base deletion/insertion (frameshift mutations)
What is a missense (point) mutation?
Where there is a single amino acid change
What is a nonsense (point)mutation?
Mutation change in a base that codes for a STOP codon early- results in non functional protein
What are the different types of large scale mutations?
- deletion/insertion (silent)
- Duplication-swapping DNA sequence around ( loss of function)
- Duplication ( gain of function)
- Translocation ( conditional- if you get a temperature and loss of protein from that)
What is an example of a base substitution (real example) ?
Deamination (C–>U)
- results in one normal strand and one mutated strand
What is the process (example) where there can be base substitution/ deletion leading to a frameshift mutation?
Depurination ( either loss of A or G)
- Strand deletes nucleotide because no base anymore and it fails to seal
- Hence frameshift mutation
- can result in short protein
Where is the mutation in the dystrophin gene?
79 exon
What are DMD and BMD commonly caused by?
- Mutations resulting in large deletions
How come BMD and DMD produce different symptoms?
- DMD allows NO FUNCTIONAL protein to be made from mutation but BMD still allows some function…but reduced
What does a BMD mutation not change?
The frame of the gene
What type of mutation occurs with a truncated protein (non functional) ?
Nonsense mutation (STOP codon)
What type of mutation occurs with a protein that has latered function due to an amino acid change?
Missense mutation
When do inversions occur (large scale chromosomal mutations)?
When a broken segment is inserted in reverse order
When does reciprocal translocation occur (large scale) ?
When NON HOMOLOGOUS chromosomes exchange segments
When do duplication and deletion occur? (large scale)
When HOMOLOGOUS chromosomes break at a different point and swap segments