Ch 7 Bacterial and Viral Genetic Systems

Question 1

minimal medium

Answer 1

medium that contains only the nutrients required by prototrophic bacteria

Question 2

complete medium

Answer 2

contains all the substances, such as the amino acid leucine, required by bacteria for growth and reproduction

Question 3

colony

Answer 3

as each bacterium grows and divides, it gives rise to a visible clump of genetically identical cells

Question 4

plasmids

Answer 4

small, usually circular DNA molecules

each possesses an origin of replication, a specific DNA sequence where DNA replication is initiated

Question 5

episomes

Answer 5

plasmids that are capable of replicating freely and are able to integrate into the bacterial chromosomes

Question 6

F (fertility) factor

Answer 6

an episome that controls mating and gene exchange between E. coli cells

Question 7

Three mechanisms bacteria exchange genetic material

Answer 7

conjugation, transformation, transduction

Question 8

conjugation

Answer 8

takes place when genetic material passes directly from one bacterium to another
DNA is transferred only from donor to recipient, with no reciprocal exchange of genetic material

Question 9

transformation

Answer 9

takes place when a bacterium takes up DNA from the medium in which it is growing

Question 10

transduction

Answer 10

takes place when bacterial viruses (bacteriophages, or phages) carry DNA from one bacterium to another

Question 11

pili

Answer 11

slender extensions of the cell membrane

Question 12

competent

Answer 12

cells that take up DNA through their cell membrane

Question 13

transformants

Answer 13

cells that receive genetic material through transformation

Question 14

cotransformed

Answer 14

genes can be mapped by observing the rate at which two or more genes are transferred together

Question 15

virus

Answer 15

a simple replicating structure made up of nucleic acid surrounded by a protein coat

Question 16

bacteriophages or phages

Answer 16

viruses that infect bacteria

have two alternative life cycles: the lytic and the lysogenic cycles

Question 17

virulent phages

Answer 17

reproduce strictly through the lytic cycle and kill their host cells

Question 18

temperate phages

Answer 18

can undergo either the lytic or the lysogenic cycle

Question 19

prophage

Answer 19

inside the cell, the phage DNA integrates into the bacterial chromosome where it remains inactive

Question 20

transductants

Answer 20

bacterial genes can be moved from one bacterial strain to another, producing recombinant bacteria

Question 21

cotransduced

Answer 21

only genes located close together on the bacterial chromosome will be transferred together

Question 22

Auxotroph

Answer 22

Bacterium or fungus that possesses a nutritional mutation that disrupts its ability to synthesize an essential biological molecule; cannot grow on minimal medium, but can grow on minimal medium to which has been added the biological molecule that it cannot synthesize

Question 23

Hfr (high frequency recombination) cells

Answer 23

F factor is integrated into the bacterial chromosome
How much of the bacterial chromosome is transferred depends on the length of time that the two cells remain in conjugation

Question 24

F’ cells

Answer 24

Cells containing an F plasmid with some bacterial genes

Question 24

Merozygote

Answer 24

Partial diploid

Cells with two copies of some genes, one on the bacterial chromosome and one on the newly introduced F plasmid