MICROBIOLOGY LECTURE 9/28

exam 2 material

mutation

change to base sequence DNA

2 ways that mutations can happen:

spontaneously and by mutagens

what are mutagens?

chemicals that cause radiation

spontaneous cell mutation

error in DNA replication

two types of mutation

indel and substitution

Substitution

swap base pair for another

Indel

add or remove nucleotide(s)

3 substitution mutations

missence, nonsense, silent

missence (substituttion) mutation

changed nucleotide = changed amino acid

silent (substitution) mutation

changed nucleotide = no change in amino acid

nonsense mutation

changed nucleotide = stop codon

2 types indel mutation

frameshift, in frame

frameshift (indel) mutation

indel shifts reading frame of gene

in frame (indel) mutation

reading frame not changed

mutation rate

how frequently mutations occur

why is HIV so hard to treat?

because of the large amounts of mutations is does per day, makes it resistant to many drugs

what do mutagens do?

increase the mutation rate

3 types of mutagens

Ionizing radiation, ultraviolet light, chemical

mutagens are often ______

carcinogens

what are carcinogens?

any substance that can cause cancer

what does the AMES test measure?

if chemicals change the mutation rate

AMES test illustrated

ok

positive ames test tells us:

chemical is a mutagen in bacteria

positive or negative ames test does not tell us whether the chemical IS or IS NOT a carcinogen

ok

What good is the ames test?

positives in the ames test are often carcinogens, not always, but usually