Chap 8- Microbial Genetics Flashcards
Mechanisms of genetic change in bacteria
Mutation & Horizontal Gene Transfer
changes in existing nucleotide sequence (that is passed on to offspring) “change in genetic material”
Mutation
transfer of DNA from one organism to another (bacteria) WITHOUT reproduction
Horizontal Gene Transfer
transfer of DNA from parent to progeny (offsprings)
Vertical Gene Transfer
Change in organisms DNA alters _____ , which also alters its _______
genotype; phenotype
sequence of nucleotides in organism’s DNA
genotype
observed characteristics of a cell
phenotype
normal , non mutated nucleotide sequence of a species
wild type
microorganism that requires organic growth factor
auxotroph (ex: mutant)
microorganism that DOES NOT require organic growth factor
prototroph
Types of Mutations
Neutral, Beneficial, Harmful
Mutation that Has no effect
Neutral
mutation that increases fitness of organism
beneficial
mutation that decreases fitness/ fatal to organism
harmful
random genetic changes passed from normal cell processes that are passed from parent to offspring
spontaneous mutations
mutation in which the wrong nucleotide has been incorporated (happens during DNA synthesis)
base substitution
change of ONE base pair (in base substitution)
point mutation
3 Possible Base Substitutions Outcomes
Silent, Missense, Nonsense
mutation that does not change the amino acid encoded (wild type amino acid)
Synonymous (silent) mutation
mutation that changes the amino acid encoded by DNA (results in different A.A)
missense mutation
mutation that generates a stop codon, resulting in a shortened protein (encodes STOP codon instead of SENSE codon)
Nonsense Mutation
Base substitutions that inactivate a gene
Null/ Knockout Mutations
Mutation resulting from the addition or deletion of a number of nucleotides not divisible by 3 (results in stop codons/non functional proteins)
frameshift mutation (REALLY BAD)
rate of mutation can be increased by a
mutagen
Rate of Spontaneous Mutations
1 nucleotide mutated for every 10^9 nucleotides
agent that increases change aka (frequency at which DNA is altered (mutated))
mutagen
genetic changes that occur due to influence outside of cell
INDUCED MUTAGENS (types- chemical or radiation)
Induced Mutation - Radiation) comes in 2 forms
Ionizing and NON Ionizing Radiation
causes molecules in cells to become HIGHLY REACTIVE; which can (forms ions that) break backbone of DNA (bc opposite charges attract)
Ionizing Radiation (XRays and Gamma Rays)
causes thymine bases to covalently bond to each other (thymine dimers that change shape of DNA), inhibiting transcription and replication
Non Ionizing Radiation (UV rays)
Effects of some CHEMICAL Induced Mutagens
modify nucleotides; change their base pairing properties
Chemical induced mutagen that converts cytosine to uracil
Nitrus Acid (HN02)
Chemical induced mutagen that adds methyl group to Guanine causing it to pair with Thymine
alkylating agents
resembles nucleotide but has different properties, causing them to be mistaken by DNA polymerase and stops replication
nucleotide analogs (some chemical behave as this) (chemical induced mutagen)
molecules that insert between adjacent base pairs in DNA strand that push nucleotides apart and create space where nucleotides can be added or deleted in New strand
intercalating agents (some chemicals act as this) (chemically induced mutagen)
2 Mechanisms for DNA repair
Proofreading Mismatch repair
repair done prior to DNA replication; done by DNA polymerase; checks accuracy; can removed incorrect nucleotides, can insert incorrect nucleotides
Proofreading
repair that fixes errors missed by DNA polymerase; an enzyme cuts the DNA near a mismatched nucleobase & removes and replacement of a short stretch of nucleotides.
mismatch repair
repair where enzyme uses light energy to break covalent bonds of thymine dimers & ONLY found in bacteria
Photoreactivation
thymine dimer repair method where enzymes removes damage and DNA Pol and ligase fills & seals gaps
Excision repair
process of transfer btwn bacteria where donor cell gives a portion of its total DNA to a recipient cell making it part of recipients DNA
Horizontal Gene Transfer
type of horizontal gene transfer where there is uptake of “naked” DNA from the extracellular environment
Bacterial Transformation
Griffith experiment showed? and how?
bacteria are capable of transferring genetic information through (transformation) by using encapsulated and un-encapsulated bacteria separately + heat killed together … where mice were still dying with both heat fixed and pathogenic bacteria introduced at same time.. as only live pathogenic bacteria was extracted from the mice
small circular piece of DNA that replicated independently of the cells chromosomal DNA
plasmid (usually transferred via conjugation)
plasmids that encode for antibiotic resistance
resistance factors (R factors)
encode for enzymes that can catabolize certain sugars or hydrocarbons
Dissimilation plasmids
type of horizontal gene transfer in which the donor cell physically contacts the recipient cell (transfer of plasmids)
conjugation
donor cell has plasmid that can become sex pilus known as
F factor (fertility factor) or F plasmid
F+ plus cells ______; F - cells _______
have F factor; do not have F factor & act as recipient cell
