Chapter 11-test 2 Flashcards
(19 cards)
Gene mutations are
random and rarely occur
Mutation rate
(1) counting # of mutations affecting a phenotype
(2) determining frequency of mutations per base pair
At the phenotypic level
mutation rates vary in different organisms from about 10-6 to 10-8
Mutations at the DNA level are
lower and more similar in different organisms; about 10-9 per base pair
germ-line mutations
Mutations that occur in germ-line cells, giving rise to sperm and egg. can be passed one gen. to next
somatic mutations
Cells not in the germ line are somatic cells. divide by mitosis and only direct descendants of original mutated cell will carry mutation
what do gene mutations do most commonly?
substitute, add, or delete one or more DNA base pairs
point mutations
localized mutations. at a specific position in a gene
Transition mutations
one purine replaces another, or one pyrimidine replaces another
Transversion mutations
a pyrimidine is replaced by a purine or vice versa. 8 are possible
Synonymous mutation
base-pair change that doesn’t alter amino acid (due to the redundancy of the genetic code)
Missense mutation
changes 1 aa in the protein
Nonsense mutation
creates a stop codon
frameshift mutations
Insertion or deletion of one or more base pairs.premature stop codons may also be produced
Some point mutations alter
the amount (but not the amino acid sequence) of protein product produced by a gene
regulatory mutations
affect regions such as promoters, introns, and the regions coding for 5’-UTR and 3’-UTR segments. three types.
promoter mutations
Mutations that alter consensus sequence nucleotides of promoters. interfere with efficient transcription initiation.
• Some promoter mutations cause mild/moderate reductions in transcription levels, others abolish transcription
true mutations are ones that
changes dna sequence
What is the most likely effect of a frameshift mutation ?
loss of protein function
