Genetics PPT 3

Question 1

Two events occur in gene exchange

Answer 1

1. Donor DNA is transferred and accepted by the
   recipient cell
2. Donor DNA is integrated on to the recipient cell’s
   chromosome or plasmid is retained

Question 2

what are the mechanisms of gene transfer

Answer 2

DNA-mediated transformation
Transduction
Conjugation

Question 3

Involves the transfer of naked DNA from the environment to the recipient cell
Cells rupture during the stationary and death phase
Recipient cell picks up a piece of the naked DNA
The naked DNA is integrated onto the recipient
chromosome

Answer 3

DNA mediated transformation

Question 4

Natural transformation occurs when bacterial cells are

Answer 4

competent

Question 5

Not all bacteria become naturally competent

Answer 5

artificial competence

Question 6

Bacterial DNA that is transferred from donor to recipient via a bacterial virus

Answer 6

transduction

Question 7

what are the two types of transduction

Answer 7

generalized and specialized

Question 8

Any part of bacterial genome can be transferred
Occurs during lytic cycle of virus replication
During viral assembly, fragments of host DNA are
mistakenly packaged into phage head forming
generalized transducing particle

Answer 8

generalized transduction

Question 9

Also called restricted transduction
Carried out only by temperate phages that have
established lysogeny
Only specific portion of bacterial genome is
transferred
Occurs when prophage is incorrectly excised

Answer 9

specialized transduction

Question 10

Only form of gene exchange in which donor survives
Is mediated by a plasmid
Requires direct contact between cells
Cells must be of opposite mating types

Answer 10

conjugation

Question 11

small, double-stranded, usually circular DNA molecules

Answer 11

plasmids

Question 12

are replicons - have their own origin of replication

vary in the number of copies present in a cell.

Answer 12

plasmids

Question 13

Confer resistance to many different widely used
antimicrobial medications and heavy metals, such as
mercury and arsenic.

Answer 13

resistance plasmids

Question 14

The movement of pieces of DNA around the genome

Answer 14

transposition

Question 15

Segments of DNA that carry genes for transposition

Answer 15

transposons

Question 16

Contain only genes encoding enzymes required for

transposition

Answer 16

insertion sequences

Question 17

• Carry genes in addition to those needed for transposition

* If one inserts on conjugative plasmid it can be transferred to another cell

Answer 17

composite transposons

Question 18

what are the effects of transposition

Answer 18

mutation in coding region, Arrest of translation or
transcription, Activation of genes, Generation of new
plasmids