Bacterial Genetics

Question 1

define mutant

Answer 1

offspring of a normal member of a species
distinct from wild type

Question 2

define mutation

Answer 2

any heritable change in DNA sequence

Question 3

define allele

Answer 3

different forms of same gene

Question 4

define isogenic strains

Answer 4

two lineages of same bacteria that have a single change

Question 5

define selection

Answer 5

growth condition that allows for growth of only a specific kind of mutant

Question 6

what are spontaneous base pair mutations

Answer 6

occuring by insertion of incorrect base during replication

Question 7

what are induced base pair mutations

Answer 7

addition of external factors (mutagens) that alter chemical bonds in DNA and need repair

Question 8

If the code is CCC (encodes proline) and it gets translated as CCA, CCG, or CCU (also encodes proline) - what type of mutation is this?

Answer 8

silent or synonymous mutations
change still results in same AA

Question 9

If the code is CCC (encodes proline) and it gets translated to CGC (arginine) or GCC (alanine) - what type of mutation is this?

Answer 9

Missense or nonsynonymous mutation

Question 10

If the code is CCC (encodes proline) and it gets translated to something with the loss of function - what type of mutation is this?

Answer 10

null mutation

Question 11

In prokaryotes what two steps in DNA synthesis occur simultaneously?

Answer 11

transcription and translation

Question 12

does a nonsynonymous mutation always lead to a change in phenotype?

Answer 12

no

Question 13

Is a mutation always beneficial to the bacterium?

Answer 13

no

Question 14

How is transcription terminated in bacteria?

Answer 14

factor dependent Rho
Rho binds rut sites not covered by ribosomes and progresses up mRNA until it hits RNA polymerase and dislodges it

Question 15

what are nonsense mutation?

Answer 15

mutations that change from coding an AA to coding for a stop codon

Question 16

what is a frameshift mutation?

Answer 16

base deletions or additions that alter reading frame of mRNA

changes function of protein

Question 17

define vertical gene transfer

Answer 17

DNA replication provides daughter cell with copy of parental cell DNA

Question 18

define horizontal gene transfer

Answer 18

evolutionary process that distributes genes between divergent prokaryotic lineages

Question 19

How does DNA move between different bacterial species?

Answer 19

horizontal gene transfer

Question 20

what is transformation in HGT?

Answer 20

uptake of naked DNA from environment and stable incorporation into the genome

Question 21

what is transduction in HGT?

Answer 21

transfer of DNA by a virus or viral vector

Question 22

what is transposition in HGT?

Answer 22

transposon genes are transferred from one organism to another through copying and insertion process

Question 23

what is conjugation or mating in HGT?

Answer 23

transfer of genetic material between bacteria to direct cell to cell contact between two cells

Question 24

what are bacterial species that are known for natural transformation/natural competence?

Answer 24

Streptococcus penumoniae
Neisseria gonorrhoeae
Haemophilus influenzae

Question 25

what does it mean for a bacteria to be naturally competent?

Answer 25

can take up DNA from environment

Question 26

How was natural competence discovered?

Answer 26

Griffith's experiment

Question 27

How does gram negative and gram positive preform transformation (HGT)?

Answer 27

translocation of ssDNA molecule into cell

Question 28

How is competence regulated?

Answer 28

Quorum sensing - high bacterial species population > build up of CSP (competence stimulating peptide) > induction of competence

Question 29

What is quorum sensing?

Answer 29

bacterial communication relays number of cells in an environment based on a secreted protein or product

Question 30

what is fratricide?

Answer 30

killing of neighboring non-competent cells as source of DNA

Question 31

what is a bacterial species that is very good at transformation/competence?

Answer 31

Streptococcus

Question 32

what is specialized transduction?

Answer 32

phage transfers small amount of bacterial DNA adjacent to phage DNA in chromosome

Question 33

what is generalized transduction?

Answer 33

transducing phage - mutation leads to misreading at pac sites, carries bacterial DNA

Question 34

what are the two types of transduction?

Answer 34

specialized and generalized

Question 35

what is a bacteriophage?

Answer 35

bacterial virus used in transduction

Question 36

what is lytic grow?

Answer 36

phage replicates > lots of phages > lysis cell > virus in environment

Question 37

what is lysogenic growth?

Answer 37

phage silently inserts into bacterial chromosome > no cell lysis

Question 38

what is prophage or lysogen?

Answer 38

lytic genes repressed, viral DNA remains silent in host

Question 39

what is conjugative transposons?

Answer 39

mechanisms of transposition transposon excises from chromosome and circularizes then transfers (conjugation) to recipient and integrates into recipient DNA

Question 40

what is conjugation?

Answer 40

transfer of DNA from donor to recipient cell

Question 41

what is a F plasmid?

Answer 41

self-transmissible plasmid has tra genes - encodes transfer apparatus

Question 42

what are the two main functions of tra genes?

Answer 42

Dtr - DNA transfer and conjugal replication Mpf - mating pair formation

Question 43

what are the steps of conjugation?

Answer 43

1. mating pair is established 2. single strand of DNA is transfered 3. DNA replication occurs in both donor and recipient cell

Question 44

what are mobilizable plasmids?

Answer 44

dont encode own Tra apparatus need Tra from self-transmissible plasmid or helper plasmid

Question 45

what a hfr strain?

Answer 45

E. coli carrying F plasmid on chromosome high frequency recombination

Question 46

What does the mixing of Hfr and F- allow for?

Answer 46

conjugation

Question 47

you can test for movement of genes with _____

Answer 47

selectable marker

Question 48

The longer it takes for a gene to be transferred the __________ the road is is located in the chromosome

Answer 48

further down

Question 49

What was the original map of E coli based on? Why?

Answer 49

based on minutes because of bacterial interrupted mating

Question 50

what are pathogenicity islands?

Answer 50

Horizontally acquired sections of bacterial chromosome that encode genes primarily associated with virulence

Question 51

How can you tell DNA is horizontally acquired?

Answer 51

look at close relatives GC content repeat sequences flanking genes Salmonella pathogenicity islands