lab 1 mutants

Question 1

antibiotic

Answer 1

a medicine that inhibits the growth of or destroys microorganisms

Question 2

antibiotic resistance

Answer 2

the ability of bacteria and other microorganisms to resist the effects of an antibiotic to which they were once sensitive

Question 3

problem of antibiotic resistance

Answer 3

treatment of an infection with antibiotics can provide selective pressure for the growth of cells that have developed resistance to the drug.

Question 4

resistance genes can be used as ..?

Answer 4

selectable markers in gene transfer experiments

Question 5

antibiotics are produced _____?

Answer 5

naturally by many organisms

Question 6

Rifampicin used to combat ____

Answer 6

infections caused by Mycobacterium tuberculosis and Mycobacterium leprae

Question 7

auxotroph

Answer 7

a mutant organisms that requires a particular nutrient that the normal strain does not
-a mutant strain that has lost its ability to synthesize one or more essential nutrients

Question 8

growth factors

Answer 8

• essential nutrients

- required for the growth of bacteria but can normally be produced by a wild type strain when grown in minimal medium

Question 9

tryptophan synthesis in wild type e.coli example

Answer 9

1) when tryptophan is present in the environment, the wild type E. coli will bring tryptophan into the cell through a cell membrane permease
2) absence of typtophan from the growth medium causes induction of the wild-type E.coli’s trp operon, a set of genes that code for enzymes needed to synthesize tryptophan. transcription of these genes allows the amino acid to be produced inside the cell and eliminates the need to uptake tryptophan from the environment

Question 10

tryptophan auxotroph

Answer 10

mutant strain that does not have the ability to synthesize its own tryptophan.
-to grow the mutant tryptophan must be provided in the growth medium

Question 11

carbon source mutant

Answer 11

a strain that has lost its ability to use a carbon source that would normally be used by the wild type

Question 12

lac- mutant

Answer 12

a carbon source mutant that is incapable of using the sugar lactose

Question 13

genotypes

Answer 13

three lower case letters in italics. + or - for particular allele for that gene
+ means the gene is present and functioning normally
- gene is missing or non-functional

Question 14

phenotype

Answer 14

dependent on genotype

-capital first letter, three letters and not italicized

Question 15

antibiotic phenotype

Answer 15

-genes for antibiotic resistance are normally give na three letter abbreviation with a fourth letter s= sensitive, r=resistant.

Question 16

defined media

Answer 16

derived from M9 medium

• M9 is a minimal medium, which means that it contains all of the elements needed for growth by the wild type E.coli, but does not contain any growth factors.
• carbon source added for energy, we can also add individual growth factors to the medium that may be required by specific auxotrophs

Question 17

complex medium

Answer 17

LB agar

• made with peptones and yeast extract, has a variety of growth factors and organic carbon sources j
• peptones excellent source of carbon and energy for mutants
• peptones and yeast extract provide growth factors required by auxotrophs

Question 18

rifampicin target

Answer 18

gram negative and positive bacteria especially Mycobacterium tuberculosis

Question 19

rifampicin mode of action

Answer 19

inhibits RNA synthesis by binding to the B subunit of the RNA polymerase so the enzyme cannot bind to DNA

Question 20

rifampicin mode of resistance

Answer 20

mutation in the B subunit prevents the drug from binding to RNA polymerase

Question 21

ampicillin targets

Answer 21

gram +ve and -ve

Question 22

ampicillin mode of action

Answer 22

inhibits peptidoglycan synthesis by preventing cross links from forming

Question 23

ampicillin mode of resistance

Answer 23

production of the B lactamase enzyme that cleaves the B lactam ring, which inactivates the antibiotic

Question 24

tetracycline target

Answer 24

gram +ve and -ve

Question 25

tetracycline mode of action

Answer 25

binds to the 30 S subunit. prevents binding of the aminoacyl tRNA to the A site of the ribosome

Question 26

tetracycline mode of resistance

Answer 26

organisms actively excretes the drug which prevents it from accumulating inside the cel

Question 27

streptomycin targets

Answer 27

most effective against gram negatives

Question 28

streptomycin mode of action

Answer 28

binds to the 30S ribosomal subunit causing tRNA mismatches, which leads to mistranslated proteins

Question 29

streptomycin mode of resistance

Answer 29

mutations in the rpsL gene (codes for the 30S ribosomal polypeptide) results in the
reduced binding of the drug

Question 30

calculating the conc. of an antibiotic added to your media

Answer 30

C1V1=C2V2