Mutations Flashcards
What is a mutation?
A change of the nucleotide sequence
What is mutagenesis?
The process of mutation generation
What are transposable elements?
Specific DNA sequences
Supernumerary (many copies)
Always contained within other DNA molecule
Move as a discrete unit
Move to random sites
Ubiquitous (present everywhere)
May insertionally activate genes or change gene expression
What are the 3 effects transposable elements can have on transcription?
- If it is inserted into an exon, a protein is produced but is not functional
- If it is inserted at the beginning of a gene, transcription is activated in other cell types
- If it is inserted away from the gene there is no effect
What is an SNP?
Single nucleotide polymorphisms
What is a transition mutation?
Change to same type of base
i.e. purine to purine, pyrimidine to pyrimidine
What is a transversion mutation?
Change to a different type of base
i.e. purine to pyrimidine or vice versa
What can single nucleotide changes do?
Change gene product (polypeptide or RNA)
Change amount of gene product
Change polypeptide length
Do not have an effect
What is a missense or non-synonymous mutation do?
Changes gene product by changing amino acid
What is a silent/neutral or synonymous mutation do?
Do not have an effect
What does a frameshift mutation or mutation of stop codon or a nonsense mutation do?
Changes the polypeptide length
What can mutations affecting regulatory sequences do?
Alter promoter activity
Alter translation initiation at AUG
Prevent mRNA splicing
Reduce mRNA stability
What are the possible structural abnormalities of chromosomes?
Deletions Duplications Inversions Substitutions/insertions Translocations Isochromosomes (2 q arms or 2 p arms fuse) Ring chromosomes Marker chromosomes
What is triploidy?
Gain of haploid set of chromosomes (3n=69)
Most common cause is polyspermy
What is aneuploidy?
Loss and gain of whole chromosomes
Caused by non-disjunction in meiosis
