Lecture 8

Question 1

What is a mutation?

Answer 1

Any heritable change or alteration of DNA

Question 2

What is haploid?

Answer 2

Bacteria have a single copy of each gene in chromosome; therefore, mutation has potential for an immediate effect on phenotype of the bacterium

Question 3

How can alterations in DNA occur?

Answer 3

• naturally

* via an external process (irradiation)

Question 4

At what rate does spontaneous or random mutagenesis?

Answer 4

• occurs at a constant rate

* 1 in 10^6 to 10^8 per generation

Question 5

How does bacterial division occur?

Answer 5

• A bacteria will duplicate its chromosome
• The cell continues to grow and starts to pinch in the middle
• The cell divides into two cells with one copy of chromosome each

Question 6

One single chromosome can encode up to how many genes?

Answer 6

3,000

Question 7

Do bacteria have histones? If not, what do they have?

Answer 7

• No, they don’t have histones

* They carry their own replication enzymes (DNA and RNA polymerases)

Question 8

When must chromosomes divide?

Answer 8

They must divide when the cell divides.

Question 9

What are point mutations? What are the different effects they can have?

Answer 9

• Point mutations are single base pair mutations

* Varied effects depending on the resulting codon

Question 10

What is a missense mutation?

Answer 10

• Mutation changes a polypeptide to inactive or non-functional.
• code for a different amino acid

Question 11

What is a silent mutation?

Answer 11

• some have little or no implication to the phenotype

* they code for the same amino acid

Question 12

What is a non-sense mutation?

Answer 12

Inserts a stop codon in place of the expected residue and can result in dramatic changes in phenotype

Question 13

Spontaneous mutations can result from what?

Answer 13

From imperfect replication of DNA or insertion of moveable genetic elements called transposons.

Question 14

What does a transposon recognize?

Answer 14

It recognizes a very small site, usually less than 10 nucleotides.

Question 15

Bacterial transpositions medically relevant in what 3 ways?

Answer 15

• often carry antibiotic resistance
• move between species and genera
• cause mutation if inserted into gene

Question 16

What is transposition?

Answer 16

It is a site specific recombination using a recombinase called a transposes. You can have a piece of DNA insertion, or a piece of circular DNA insert to get site specific recombination.

Question 17

What does tranposase allow?

Answer 17

Entry into target cells

Question 18

What does resolvase do?

Answer 18

homologous recombination

Question 19

What is selection?

Answer 19

Drug resistance allows you to find the rare spontaneous mutation. It does not effect the rate at which it occurs. It can happen when someone doesn’t use their antibiotic correctly.

Question 20

What are the steps in genetic mutation causing drug resistance?

Answer 20

• non-resistant bacteria exist
• bacteria multiply by the billions
• some mutations make the bacterium drug resistant
• drug resistance bacteria multiply and thrive

Question 21

What are the steps in bacterial transformation?

Answer 21

• donor bacterium
• cell lysis
• binding to recipient
• DNA uptake
• recombination

Question 22

What is lysis?

Answer 22

Strands of DNA are loose and bind to the bacterium and become part of the nucleoid region.

Question 23

What are plasmids?

Answer 23

• transposons can be located in the extrachromosomal DNA
• circular, supercoiled
• one or more different plasmids per cell
• one or more copies of the same plasmids per cell

Question 24

How are plasmids mobile?

Answer 24

They can be transferred between different bacteria species. Bacteria can obtain DNA from other bacteria.

Question 25

What do plasmids encode?

Answer 25

They encode antibiotic resistance genes (problem for multiple antibiotic resistance) *also encode virulence factors (adhesions, toxins)

Question 26

What is bacterial conjugation?

Answer 26

Bacteria interact or adhere to surfaces and each other through filaments on the surface called pili (fimbrae).

Question 27

How can genetic material be transferred in bacteria?

Answer 27

By bacterial conjugation, but it must have direct contact to occur.

Question 28

How can you tell the gender of bacteria?

Answer 28

* Male is F +, carries F plasmid, makes sex pilus | * Female is F -, no F plasmid, no sex pilus

Question 29

What is F in bacterial genetics/gender and sexduction?

Answer 29

F is fertility. Direct contact of an F + donor male with an F - recipient female via the sex pilus results in transfer or conjugation of the F plasmid.

Question 30

What is the net result of F (fertility)?

Answer 30

The net result is conversion of the F - female recipient to an F + male.

Question 31

What is required for conjugation to happen?

Answer 31

* donor cell must have a F plasmid (compatible sex pilus) * requires direct contact between two bacterial cells via a pilus structure * DNA in the donor cell is transferred through the pilus and into the recipient cell

Question 32

What does bacterial transduction require?

Answer 32

viruses

Question 33

What is the process of phage infection?

Answer 33

* virus makes contact * virus introduces its DNA into the bacteria * bacteria can use enzymes that digest foreign DNA not self DNA

Question 34

What is required for transduction to happen?

Answer 34

* donor cell must carry a temperate bacteriophage (virus) * requires a specific lysogenic bacteriophage to transfer host genes from a donor bacterial strain to a recipient bacterial strain * new genes are integrated at the site of phage integration

Question 35

What are the steps of transduction?

Answer 35

* donor is infected with phage * cell lysis by phage donor DNA in phage particle * injection of donor DNA into recipient cell (recombination) * recipient transductant with donor DNA

Question 36

Spontaneous mutations can result from imperfect replication of DNA or by the insertion of moveable genetic elements called ____?

Answer 36

Transposons

Question 37

What is the order for the selection of antimicrobial resistance?

Answer 37

1. Non-resistant bacteria exist 2. Bacteria multiply by billions 3. Mutations make organisms drug resistant 4. Drug resistant organisms multiply and thrive.

Question 38

What are some true statements about transduction?

Answer 38

* transduction requires viruses * transduction requires a specific lysogenic bacteriophage * transduction mainly occurs via injection * does not occur with animal viruses