CH16 Flashcards
(38 cards)
total genetic potential of MO, code in its DNA
gene
the DNA that is expressed by the MO under a given set of conditions
phenotype
change in nucleotide sequence, may result in change of protein
mutation
types of mutations
mutant/wild type
spontaneous
induced
product of the standard “normal” allele at a locus, in contrast to that produced by a non-standard, “mutant” allele
wild type mutation
errors that lead to changes in DNA
spontaneous mutation
exposed to chemical or physical agent
induced mutation
- damage DNA
- alter DNA chemistry
- interfere with repair mechanism
mutagen
point mutations can be
silent
missense
nonsense
- AAU–>AAC
- both code for same AA
- protein unaltered
- no consequence for organism
silent point mutation
- GAG–>GUG
- AA is different
- significant but not always deadly
- sickle cell anemia
missense point mutation
- UAU–>UAA
- stops instead of AA
- non functional product protein fragment
nonsense pont mutation
insertion or deletion of nucleotide
frameshift mutations
describe the Ames Test
- The Ames test is based on the observation that many carcinogens also are mutagens.
- The test determines if a substance increases the rate of mutation; that is, if it is a mutagen. If the substance is a mutagen, then it is also likely to be carcinogenic if an animal is exposed to it at sufficient levels
what was Bruce Ames procedure for his experiment with histidine + Salmonella
- had culture of Salmonella histidine auxotroph and added it to a plate with complete medium and small amount of histidine (control) and to a plate that had medium with test mutagen and small amount of histidine
- incubated at 37 degrees C for a day or two
- the control plate had spontaneous revertants and the other had revertants induced by the mutagen
- if numbers are larger on mutant plate than control, then the revertants are induced by mutagen
why add liver enzymes to the Ames test?
alfotoxins (produced by fungus) are mutagenic when broken down and makes results more accurate
exchange/combining of genetic material from two organisms
recombination
recombination in eukaryotes and prokaryotes
-eukaryotes
diploid; crossing over b/t chromosome pairs (meiosis)
-prokaryotic
transfer of pieces of DNA from a donor bacterium to recipient (another bacteria)
incorporate into recipient DNA
mechanisms of DNA transfer
conjugation
transformation
transduction
cell to cell contact, depends on presence of plasmids
conjugation
recipient bacterium takes up “free-floating” DNA
transformation
bacterial virus (phage) transfers DNA from donor to recipient
transduction
small pieces of extra DNA
plasmids
how are plasmids independent of host chromosome
- can be eliminated (hi temp, starvation)
- multiple copies
- some can integrate with chromosome (episome)