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Question

Which method(s) is(are) not used by bacteria to introduce genetic variation?

a. Transformation
b. Fertilization
c. Conjugation
d. Transduction

Answer 1

You are all wrong the answer is only b

Most bacteria reproduce by binary fission.

Transfer and recombination of Bacterial genes:

There are three natural processes of gene transfer in bacterium:
1. Transformation: Bacteria picks up DNA from its environment. Avery's experiment.
2. Transduction: Gene transfer from one bacterium to another using a bacteriophage.

a). General transduction: random pieces of host DNA are packaged in within a phage capsid during the lytic cycle.
b). Restricted transduction: when a temperate phage takes some of the host's DNA with it when it forms a new virus.

3. Conjugation: transfer of genetic material between 2 cells that are temporarily joined.

a). The cell donating the DNA extends an external appendage called a sex pili.
b). This pili attaches to the cell receiving the DNA.
c). A cytoplasmic bridge forms which the DNA is transferred.

The ability for the sex pili to form is conferred by genes in a plasmid called the F factor. (fertility factor). Cells with the F factor are designated F+ and cells without it are designated F-. During conjugation between an F+ and an F- bacterium both cells finish up as F+ forms. Sometime the the F factor inserts into the circular chromosome. Integrated F factor is still expressed. It is designated Hfr. (high frequency of recombination).

Transfer of genetic material by conjugation can help scientists map the chromosomes of bacteria.
1. Specific strains of Hfr bacteria always transfer genes in the same sequence.
2. The duration of conjugation determines the number of genes transferred.


Plasmids:
Episomes: plasmids that can integrate into the bacterial chromosome. ( F factor). Can exist independently of the circular chromosome or integrate and replicate with it. Some carry up to 7 genes for resistance for certain antibiotics.

Transposons: DNA sequences that can move from one chromosomal site to another. Serve as natural agents of genetic change. Occur in both prokaryotic and eukaryotic cells.

Answer 2

A and B

bacteria do not use both methods to introduce genetic variation.
transformation - artificial and not done by the bacteria
fertilisation - bacteria undergoes asexual reproduction so it doesn't and cannot be fertilised. the only form of 'fertilisation' the bacteria does is conjugation.

Answer 3

He's right, it's A and B....

(Transformation can also introduce genetic variation, but it's not done by the bacteria.)

Answer 4

a and b