Gene Mutations Flashcards
(32 cards)
What is a mutation
A change in the nucleotide sequence that can be passed on from one cell or organism to another
What are somatic mutations
Occur in body cells , passed to daughter cells in mitosis but not to offspring
What are germ line mutations
Occur in cells that gives rise to gametes, passed to offspring at fertilization
What are loss of function mutations
Gene is not expressed at all or protein doesn’t function, nearly always recessive
What are gain of function mutations
Produces a protein with altered function, usually dominant, common in cancer
What are conditional mutations
Phenotype is altered only under certain conditions
What is a reversion mutation
The gene is mutated a second time and DNA reverts to the original sequence or to a different sequence that results in the non-mutant phenotype
What are point mutations
Insertion / deletion of a single base pair or substitution of one base pair for another
What are silent mutations
Substitution that results in a codon that codes for the same amino acid
What is a missense mutation
Substitution resulting for a different amino acid
What is a nonsense mutation
Base substitution results in a stop codon somewhere in the mRNA
What is a loss of stop mutation
Base pair of substitution that changes a stop codon to a sense codon, extra amino acids are added to the polypeptide
What is a frame shift mutation
Insertion / deletion of a base pair - produces nonfunctional proteins
What do promoter mutations alter
Alter the rate of transcription of the gene
What may mutations at RNA splicing sites lead to
May lead to abnormal mRNA
What do chromosomal rearrangements result in
Results in extensive changes in DNA - can break + rejoin
What are 4 types of chromosomal rearrangements
- deletion
- duplication
- inversion
- translocation
What is a deletion chromosomal rearrangement
Chromosome breaks in two places + rejoins, leaving out part of the DNA
What is a duplication chromosomal rearrangement
Homologous chromosomes break at different positions + reconnect to the wrong partners
What is an inversion chromosomal rearrangement
Chromosome breaks + rejoins with one segment flipped
What is a translocation chromosomal rearrangement
Segment of DNA breaks off + attaches to another chromosome, can cause duplications + deletions
What is an endogenous retrovirus
The viral DNA can remain in the host genome + be passes from one generation to the next
What do transposons do
Insert themselves into genes + cause mutations
Via what 3 mechanisms can spontaneous mutations occur
- mistake during replication = template base undergone a chemical rearrangement
- chemical reactions can alter bases = loss of an amino group
- meiotic errors = nondisjunction + random breaking + rejoining of chromosomes
