Mutations Flashcards
What is a mutation?
Heritable alteration in gene or chromosome
and
the process that produces the alteration
What are the types of causes of mutations?
Exogenous causes
Endogenous causes
What are the types of exogenous causes of mutations?
Ionising radiation
Chemicals
Anti-cancer agents
What are the types of endogenous causes of mutations?
DNA replication defects
Transposable elements
How are mutations caused?
DNA damage
and then defective DNA repair
What are transposable elements?
Sections of DNA that can move as one unit to random sites in rest of DNA
Are transposable elements longer or shorter than genes?
Longer than genes
Do transposable elements exist in the free form?
No
they’re always contained in DNA molecules
Are transoposable elements more likely to move into longer genes or shorter genes?
More chance of them moving into longer genes
How can transposable elements cause mutations?
Can transpose into genes
disrupt gene
product product is dysfunctional
Can transpose into promoter region of gene
activate gene when it shouldn’t be
How can transposable elements have no effect?
If transpose into non-coding sections of DNA
or introns
What are the types of mutations?
Micro
Macro
What is the difference between micro and macro mutations?
Micro - few bases affeced
Macro - whole areas of chromosomes affected
What are the types of micro mutations?
Substitution
Insertion
Deletion
What are the types of macro mutations?
Translocation
Inversion
Duplication
Deletion
What are the types of substitution mutations?
Transition/transversion
Mis-sense/nonsense/silent/non-stop
What is a transition substitution mutation?
Base change to same type of base
- purine to purine
- pyrmidine to pyrimidine
What is a transversion substitution mutation?
Base change to different type of base
- purine to pyrimidine
- pyrimidine to purine
What is a mis-sense substitution mutation?
Causes change in amino acid in protein
How does a mis-sense substitution mutation affect the polypeptide?
Changes conformation of polypeptide
What is a non-sense substitution mutation?
Creates early stop codon
How does a non-sense substitution mutation affect the polypeptide?
Polypeptide production stopped prematurely
polypeptide is shorter length
What is a silent substitution mutation?
Same amino acid coded for
How does a silent substitution mutation affect the polypeptide?
Has no effect on it
What is a non-stop substitution mutation?
Stop codon now codes for an amino acid
How does a non-stop substitution mutation affect the polypeptide?
Polypeptide production carries on
longer polypeptide produced
What is an insertion mutation?
Addition of a few extra nucleotides into DNA strand
What is a deletion mutation?
Removal of a few nucleotides from DNA strand
What do insertons/deletions commonly lead to?
Frameshift
How can insertions/deletions lead to frameshifts?
Insertion/deletion of 1/2/4/5/7/8 etc. bases
What is a frameshift?
Downstream bases shift to right or left
gives different codons
How do frameshifts affect the polypeptide? Why?
Different conformation due to different amino acid
Short, longer polypeptide due to early, later stop codon
How can insertions/deletions not lead to frameshifts?
Insertion/deletion of 3/6/9 etc. bases
Why do insertions/deletions of 3/6/9 etc. bases not lead to frameshifts?
Add or remove codons
but rest of codons remain the same
How does an insertion/deletion of 3/6/9 etc. bases affect the polypeptide?
Different conformation due to extra or missing amino acids
What are the types of translocations?
Reciprocal
Robertsonian
What is an inversion?
Section of chromosome flipping over
What is a duplication?
Section of chromosome copying itself
What is a macro deleton?
Section of chromosome being lost
How can mutations affect transcription?
Alter promoter activity
Alter mRNA splicing
How can mutations affect translation?
Alter translation initiation
What are the consequences of mutations affecting transcription, translation?
Change amount of produced
How can mutations affect promoter activity of genes?
Affect binding of transcription factors, RNA polymerase
How can mutations affect mRNA splicing?
Alter intron-exon junction
affecting recognition by spliceosome
How can mutations affect translation inititation?
Affect start codon AUG
recruitment of methionyl tRNA, ribosome
