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Frequently asked questions in bacterial genetics |
1. What is mutation?
- Sudden heritable change in a nucleotide sequence. They are
classified as base substitution, frame shift mutation and
insertional inactivation.
2. What is base substitution mutation?
- When one base is inserted in place of another, it is base
substitution, when this results in a codon that causes a wrong
amino acid to be inserted, it is missense mutation and when a base
substitution results in the generation of a termination codon, it
is nonsense mutation.
3. What are the methods of gene transfer between bacteria?
- Transformation, conjugation and transduction.
4. What are the transposons or “jumping genes”?
- These are pieces of DNA that move from one site to the
another, either within or between the DNA of bacteria, plasmids
and bacteriophage.
5. What is the significance of Transposons?
- They can code for drug resistance, enzymes and toxins.
- They can cause mutation in genes, where they insert. Such
mutations are called insertional mutagenesis.
6. What is transduction?
- It is the transfer of DNA from one bacterium to the another
by a bacteriophage.
7. What is conjugation?
- It is the process of genetic transfer where a bacterium with
F plasmid (F+) mates with another bacterium (F-) and sends a
strand of F plasmid DNA into the recipient cell through sex pili.
8. What is F factor?
- The transfer factor, also called fertility factor is a
plasmid that codes for the synthesis of sex pili and self
transfer.
9. What is R factor?
- It is a plasmid that codes for drug resistance. Its transfer
to other bacteria is independent of F factor.
10. What is an episome?
- It is a plasmid, which is known to integrate itself with the
bacterial chromosome.
11. What is the significance of plasmids?
- They code for the following properties:
• Antibiotic resistance.
• Resistance to heavy metals, such as Hg, Ag.
• Resistance to UV light, which is mediated by DNA repair enzymes.
• Pili, exotoxins and bacteriocines.
12. What is sexduction?
- The F factor is usually an episome that integrates itself
into the bacterial chromosome. When such episome is transferred to
F- cells during conjugation, some of the host chromosomal genes
are also transferred.
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