Question

Microbiology!

1. If allolactose is not present, the lac repressor will stay bound to the operator, and the lac operon will not be transcribed. TRUE OR FALSE

2. The transfer of a plasmid from one cell to another through direct cell-to-cell contact is called _____________.

-Transformation

-Mutation

-Transduction

-Conjugation

3. Bacteria that can naturally take up free DNA and recombine it into their chromosome are called ______________.

- F+ cells

-transformed

-competent

-transduced

Answer 1

1. If allolactose is not present, the lac repressor will stay bound to the operator, and the lac operon will not be transcribed.

Answer:TRUE

Explanation;

lacI gene is regulator gene of lac operon , It has it’s own promoter Plac I when when RNA polymerase bind to promoter region and lead transcription of lac I and after translation lac repressor protein will synthesized .Four monomer together form active tetramer lac repressor, that can tightly bind to the operon site(Olac) and prevent transcription of lac operon.

When lactose is present in the cell some amount of it is converted into allolactose by enzyme bita –galactosidase .Allolactose bind to the active lac repressor tetramer and then the repressor cannot bind to the operator region(Olac) and transcription occur by bining of RNA polymerse in this Olac region.So the stament is true.

2. The transfer of a plasmid from one cell to another through direct cell-to-cell contact is called _____________.

Answer:Conjugation

Explanation:

Conjugation is one the process of genetic recombination by which genetic material exchange between two cells of bacteria through a conjugation tube.To make conjugation tube donor bacteria and recipient bacteria must be in cell to cell contact.Which donate DNA called donor bacteria orF+ and which one taking DNA called DNA called recipient or F-.

In transformation the exchanging of genetic material pass through liquid medium from donor cell to recipient cell.

In transduction genetic recombination takes place by exchanging genetic material through a bacteriophage virus from donor cell to recipient cell.

So conjugation is the right answer.

3. Bacteria that can naturally take up free DNA and recombine it into their chromosome are called ______________.

Answe:transformed

Explanation:

In transformation more specifically in natural transformation recipient bacteria taking up naked DNA from environment and then incorporate it into their chromosome.Naked DNA come in environment from donor bacteria .The bacteria involved in transformation called transformed.