Mutations Flashcards
mutations
- change in the nucleotide sequence of DNA that can be passed down from one cell or organism to another
- classified by the chromosomes or proteins they affect
induced
caused by mutagens, which are environmental factors such as chemicals and radiation
mutation hot spots occur where bases are more susceptible to mutation
heritable
mutations are changes in the nucleotide sequence that can be passed down from one cell or organism to another
daughter cell: mitosis
offspring: sexual reproduction
somatic mutation
occurs in somatic body cells
passed down via mitosis
germ line mutation
occurs in cells that give rise to gametes, passed down at fertilization
mutations during the cell cycle
errors in replication by DNA polymerase
imperfect meiosis - nondisjunction and random breaking and rejoining of chromosomes
point mutation
smallest possible sequence change
insertion, deletion, substitution
substitutions
transition: substitution of one pyrimidine for the other (or purine -> purine)
transversion: substitution of a pyrimidine for a purine or vice versa
frame shift mutation
causes a different protein to result from translation
created by insertions and deletions not in multiples of 3
everything downshift of the mutation will shift
phenotype mutations
sequence level mutations can be classified by the effect they have on the phenotype
silent, nonsense, misense
missense
different sequence of amino acids
some just change one or a few amino acids (substitution)
some change a lot of the amino acids or result in large proteins (insertion or deletion that causes a frameshift)
nonsense
no protein is produced
promoter, start codon, premature stop codon
silent
does not change the protein
result of redundancy, non-coding regions, introns, etc.
deletions
chromosome may break in two places and rejoin, leaving out part of the DNA
chromosomal mutations
worker on a larger, structural scale
occur when DNA molecules break and are rejoined incorrectly
caused by chromosomal damage due to mutagens or by errors in chromosomal replication
duplications
two homologous chromosomes break at different places and rejoin incorrectly
duplication of one homolog and deletion of the other
inversions
chromosomes breaks and rejoins with one segment flipped
translocations
segment of DNA breaks off and attaches to a non-homologous chromosome
basis for gene diversity
spontaneous mutations
starts with a base changing its configuration
a rare tautomer may be able to pair with a different base
rare tautomer of cytosine (NH3 disrupted) pairs with adenine instead of guanine
nitrous acid
- starts with changes in a base
- cytosine undergoes deamination to turn into uracil via nitrous acid
- permanent effect of both spontaneous and induced mutations is most evident after the mutated strand undergoes replication
chemical mutagens
benzopyrene adds a chemical group to guanine to prevent base pairing
when DNA polymerase comes across this, it adds a random base
radiation mutagen
ionizing radiation creates highly reactive free radicals that can change bases into non-recognizable forms
ionizing radiation can break the sugar backbone of DNA
UV radiation can create thymine dimers in adjacent thymine in DNA strands
