Bacterial Genetics

Question 1

auxotroph

Answer 1

mutant that requires a growth factor

Question 2

prototroph

Answer 2

does not require a growth factor

Question 3

silent/synonymous mutation

Answer 3

change that generates codon that translates into the same amino acid as original

Question 4

missense mutation

Answer 4

altered codon codes for a different amino acid (often this will cause the mutant cells to grow slowly)

Question 5

nonsense mutation

Answer 5

early stop UGA, UAA, UAG

Question 6

null/knockout mutation

Answer 6

totally inactivates gene

Question 7

transposon

Answer 7

DNA that can jump into the host genome, may enter cell through a plasmid - can move into host cell genome and jump in at different sites may be replicated then leave again as plasmid. Often makes genes dysfunctional

Question 8

plasmids

Answer 8

can exist in bacteria/archaea/eukarya/yeasts
circular double stranded DNA molecules
Have origin of replication (can be passed on through replication)
generally do not encode useful info
narrow host range - normally very specific

Question 9

mobilizable plasmids

Answer 9

origin of transfer but lack other genetic info for transfer - they can transfer when conjugative plasmid is present

Question 10

conjugative plasmids

Answer 10

carry all the genetic info needed for transfer

Question 11

Resistance or R plasmids

Answer 11

encode resistance to antimicrobial chemicals (including antibiotics)

Question 12

What are the components of the the simplest transposon? What is the simplest transposon?

Answer 12

insertion sequence (IS) transposon is the simplest
only incodes transposase gene (which makes enzyme for transposition) and inverted repeats

Question 13

non-homologous recombination

Answer 13

DNA recombination that does not require extensive nucleotide sequence similarity in the streches that recombine

Question 14

genomic island

Answer 14

large segment of DNA in cell’s genome that originated in different species

Question 15

pathogenicity islands

Answer 15

genomic islands that contain genes that increase the disease-causing abilities of the bacterium

Question 16

core genome

Answer 16

conserved genes of the species

Question 17

mobile genome

Answer 17

very different genes that make up certain strains, can move from one DNA molecule to another

Question 18

what are some mobile genetic elements

Answer 18

phage DNA, plasmids, transposons, genomic islands

Question 19

direct selection

Answer 19

used to isolate mutants that can survive conditions that their parents can’t

Question 20

indirect selection

Answer 20

used to isolate auxotrophic mutant from prototrophic parent strain

• difficult to do b/c both grow on medium so
• replica plating is used

Question 21

what can be transfered from one cell to another by conjugation?

Answer 21

plasmid DNA

chromosomal DNA

Question 22

which kinds of mutations do chemical mutagens cause?

Answer 22

frameshift and base substitutions

Question 23

mutagens that modify nucleobases change what properties?

Answer 23

base pairing

Question 24

what chemicals did you learn about that add alkyl onto nucelobases and create mutations?

Answer 24

alkylating agents

Question 25

Base analogs

Answer 25

structurally resemble nucleobases but have different hydrogen bonding properites but can be mistaken as nucleotides and then put into DNA creating mutation

Question 26

chemical mutagens that squeeze between base pairs and induce frameshift mutations are called

Answer 26

intercalating agents

Question 27

which DNA segments increase the rate of mutations by inserting themselves into DNA and inactivating them?

Answer 27

Transposon can move form different sites on host genome, into host genome, out of host genome to plasmid and this can create mutations

Question 28

what are the mutagenic types of radiation?

Answer 28

ultraviolet light - can cause thymine dimers to form

X-rays - cause breaks in DNA (double and single stranded)

Question 29

reversion

Answer 29

when mutation changes back to original non-mutated state (occurs spontaneously and at low frequencies)

Question 30

why would you give two antimicrobial medications?

Answer 30

because the rate of mutation is very low, so the likelihood that the a cell simultaneously, spontaneously becomes resistant to both is very low

Question 31

base substitution

Answer 31

most common type of mutation, during DNA synthesis when an incorrect nucleotide is incorporated

Question 32

point mutation

Answer 32

if only one base pair is changed

Question 33

base substitutions increase when…?

Answer 33

ROS (reactive oxygen species) are around in aerobic environments because the oxidize guanine which leads to more mistakes

Question 34

what is naked DNA

Answer 34

free floating DNA

Question 35

DNase

Answer 35

enzyme that degrades DNA - can only degrade free floating when free floating

Question 36

what is the specific physiological state that allows the cells to take up DNA

Answer 36

competent state - some cells only reach competent state when recourses are low or cell density gets low (not very many bacterial cells)

Question 37

how many strands of donor DNA integrate into a recipient chromosome during transformation?

Answer 37

one