Chapter 6 Conjugation

Question 1

Bacteria are useful genetic models because:
_______: fewer genes and fewer bases than other organisms
_______: mutations can be observed directly because there is one copy of each gene
_______: can be measured in minutes
_______: allow detection of rare events
_______: bacterial culture is easy and inexpensive and takes up very little space
_______: mutants are easily created, identified, isolated, and manipulated for study

Answer 1

1) genome simplicity
2) haploid genomes
3) short generation times
4) enormous # of progeny
5) ease of propagation
6) heritable differences

Question 2

Bacteria genomes are usually composed of a _______, which carries mostly essential genes

Answer 2

single chromosome

Question 3

The _______ is usually covalently closed, circular molecule of double-stranded DNA

Answer 3

Bacterial Chromosome

Question 4

_______: small double-stranded circular DNA molecules containing nonessential genes in bacteria

Answer 4

plasmids

Question 5

An _______ plasmid carries antibiotic resistance genes that can be transferred to recipient cells

Answer 5

R (resistance)

Question 6

The ________ plasmid contains genes that promote its own transfer from donors to recipients

Answer 6

F (fertility)

Question 7

_______ plasmids can replicate independently of the bacterial chromosome so that the number of plasmids per cell can increase rapidly

Answer 7

high-copy-number plasmids

Question 8

_______ plasmids are present in one or two copies per bacterial cell and usually cannot replicate independently of the bacterial chromosome

Answer 8

low-copy-number plasmids

Question 9

What are the 3 types of recombination in prokaryotes?
- Each method involves ________ transfer of genetic material from a donor cell to a recipient cell

Answer 9

1) conjugation
2) transformation
3) transduction
- One-way

Question 10

_______ is the transfer of replicated DNA from a donor to a recipient

Answer 10

conjugation

Question 11

_______ is the uptake of DNA from the environment

Answer 11

Transformation

Question 12

_______ is the transfer of DNA from one bacterium to another by a viral vector

Answer 12

transduction

Question 13

genetic information is transferred through a hollow tube, called a _______

Answer 13

conjugation pilus

Question 14

Donor cells possess an F factor and are called _______

Answer 14

F+ cells

Question 15

Recipients lack an F factor and are called _______

Answer 15

F- cells

Question 16

A bacterial strain containing ampR _______ grow on ampicilin

Answer 16

will

Question 17

A bacterial strain containing ampS _______ grow on ampicilin

Answer 17

won’t

Question 18

After conjugation, the recipient cell is called the _______ cell

Answer 18

exconjugate

Question 19

Describe the mechanism for Conjugation I (4)

Answer 19

1) Conjugation pilus forms
2) Gene expression produces relaxosome
3) Relaxosome cleaves 1 bond on the T strand
4) Relaxosome degrades leaving relaxase on 5’ end of T strand

Question 20

Describe the mechanism for Conjugation II (3)

Answer 20

1) relaxase facilitates T strand through conjugation pilus
2) rolling circle replication begins at Ori-T of donor cell
3) recipient cell uses transferred DNA as template for replication

Question 21

A large component of the F factor consists of 4 _______ elements

Answer 21

insertion sequence

Question 22

IS elements are mobile segments of bacterial DNA that can _______ themselves to new locations

Answer 22

transpose

Question 23

Circular elements, like the F factor, can integrate into the bacterial chromosome to form an _______

Answer 23

episome

Question 24

When the formation of an episome occurs with an F factor, the cell is called a _______ cell

Answer 24

Hfr (high frequency recombination)

Question 25

In Hfr gene transfer, the complete transfer of the bacterial chromosome is not accomplished leading to a _______ fragment

Answer 25

double-stranded LINEAR

Question 26

After conjugation of the partial T strand, homologous _______ occurs between transferred DNA and circular chromosome recipient
- then the transferred strand gets _______

Answer 26

recombination
degraded

Question 27

Donor cells carrying F’ factor are called

Answer 27

F’ cells

Question 28

An F’ donor bacterium contains a functional F factor derived from _______ excision of the F factor from an Hfr Chromosome

Answer 28

aberrant (imperfect)

Question 29

exconjugants that contain complete F’ factor are called _______ because they contain 2 copies of the bacterial chromosome genes found on the F’ factor

Answer 29

partial diploids

Question 30

_______ = a state when a partially diploid bacterial cell is produced

Answer 30

merozygote