Mutations, Ames test, Genetic recombination

Question 1

Mutation

Answer 1

a change in phenotype due to change in genotype (nitrogen base sequence of DNA)

Question 2

wild type

Answer 2

A natural, nonmutated characteristic is known as a wild type (wild strain)

Question 3

Define mutant strain

Answer 3

An organism that has a mutation is a mutant strain, showing variance in morphology, nutritional characteristics, genetic control mechanisms, resistance to chemicals, etc.

Question 4

Isolating Mutants Replica
- plating technique allows identification of mutants:

describe process (a-d)

Answer 4

a) Culture is exposed to mutagen

(b) Isolated colonies are transferred on a master plate

(c) tiny clump of cells are picked up and transferred to a plate with complete medium and another with incomplete medium

(d) Colonies in the complete medium plate missing from the incomplete one are mutant colonies that can be subcultured for further use

Question 5

Define spontaneous mutations

Answer 5

random change in the DNA due to errors in replication that occur without known cause

Question 6

Define induced mutations

Answer 6

result from exposure to known mutagens, physical (primarily radiation) or chemical agents that interact with DNA in a disruptive manner

Question 7

Any chemical capable of mutating bacterial DNA can similarly mutate what?

Answer 7

mammalian DNA

Question 8

What 3 things can the Ames Test screen for?

Answer 8

Agricultural, industrial, and medicinal compounds are screened using

Question 9

What is the indicator organism, that is a mutant strain, that has lost the ability to synthesize histidine

Answer 9

Salmonella typhimurium is HIS (-)

Question 10

If the his (-) culture of salmonella becomes his (+) it means

Answer 10

it is highly, increasingly, mutagenic then bacteria will become HIS (+)

Question 11

Describe control setup of Ames test

Answer 11

bacteria plated on a histidine-free medium containing liver enzymes but NO test agent

EXPECT NO GROWTH

Question 12

What would you expect of control plate if his(+) arises? after 12 h incubation

Answer 12

his(+) colonies arising from spontaneous back-mutation

little growth

Question 13

describe the test plate conditions of Ames test

Answer 13

plated on a histidine-free medium containing liver enzymes AND test chemical

Question 14

Describe expected results of test plate his (+) colonies after 12 h incubation

Answer 14

his(+) colonies in presence of the chemical

causes mutations mutant

Question 15

ames fluctuation test using multiple wells

what does blue well indicate?

Answer 15

no back-mutation

Question 16

ames fluctuation test using multiple wells

what does yellow well indicate?

Answer 16

indicates back-mutation

Question 17

Define Genetic recombination

Answer 17

occurs when an organism acquires and expresses genes that originated in another organism

Question 18

3 means for genetic recombination in bacteria:

Answer 18

1. Conjugation
2. Transformation
3. Transduction

Question 19

Conjugation

Answer 19

Transfer of a plasmid or chromosomal fragment from a donor cell to a recipient cell via direct contact

Question 20

for conjugation, what allows the synthesis of a conjugative pilus of a gram-negative cell donor

Answer 20

Gram-negative cell donor has a fertility plasmid (F factor) that allows the synthesis of a conjugative pilus

Question 21

How does Donor (F+ cell) transfers fertility plasmid through? what is the recipient cell?

Answer 21

Donor (F+ cell) transfers fertility plasmid through pilus to recipient (F- cell), which becomes F+ cell

Question 22

Some F+ cells become what

Answer 22

Hfr cells (high frequency of recombination)

High-frequency recombination – donor’s fertility plasmid is integrated into the bacterial chromosome

Question 23

Transformation

Answer 23

Chromosome fragments from a lysed cell are accepted by a recipient cell; the genetic code of the DNA fragment is acquired by the recipient

Question 24

for transformation, Donor and recipient cells can be unrelated – T or F?

Answer 24

T

Question 25

what is a useful tool in recombinant DNA technology?

Answer 25

transformation

Question 26

do the donor and recipient cell have to be related to exchange genes?

Answer 26

no

Question 27

Streptococcus pneumoniae describe G (+) or (-) and shape

Answer 27

Gram+ cocci that occur in pairs or chains.

Question 28

Encapsulated strains: Cells of virulent stains of S. pneumoniae are surrounded by a polysaccharide capsule which protects them from being digested by

Answer 28

phagocytic white blood cells.

Question 29

Unencapsulated strains: Those with no capsule/glycocalyx are normal microbiota of lungs, sinuses and middle ear of 75% of people. does it cause disease?

Answer 29

no

Question 30

Transduction

Answer 30

Bacteriophage serves as a carrier of DNA from a donor cell to a recipient cell

Question 31

what are the two types of transduction?

Answer 31

generalized and specialized

Question 32

Generalized transduction

Answer 32

random fragments of disintegrating host DNA are picked up by the phage during assembly; any gene can be transmitted this way

Question 33

Specialized transduction

Answer 33

a highly specific part of the host genome is regularly incorporated into the virus

Question 34

Transposons

Answer 34

Special DNA segments that have the capability of moving from one location in the genome to another – “jumping genes”

Question 35

Transposons function

Answer 35

• Cause rearrangement of the genetic material
• Can move from one chromosome site to another, from a chromosome to a plasmid, or from a plasmid to a chromosome
• May be beneficial or harmf

Question 36

is conjugation direct or indirect?

Answer 36

direct

Question 37

is transformation direct or indirect?

Answer 37

indirect

Question 38

is transduction direct or indirect?

Answer 38

indirect