bacterial genetics

Question 1

list qualities of the bacterial genome

Answer 1

• haploid
• circular chromosome
• dsDNA
• some episomal elements (plasmids)
• transferable DNA
• they have viruses

Question 2

are DNA CpG dinucleotides methylated

Answer 2

no - unmethylated

Question 3

what is a plasmid

Answer 3

• typically circular (few linear)
• dsDNA
• serparate from the chromosomal DNA
• some have a suicide gene to ensure maintenance
• some are transmissible by conjugation
• variable in sizes and copy number

Question 4

how do bacteria vary their genome to evolve

Answer 4

• mutation of genes
• transfer of genes
• rearrange their DNA
• delete genes
• new genes inserted

Question 5

what effects can mutations have on bacteria

Answer 5

• none
• be lethal
• alter fucntion/properties

Question 6

outline the process of transcription and translation and postranslational events of proteins in bacteria

Answer 6

transcription = DNA –> RNA
translation = RNA –> proteins

Question 7

through which methods does introduction of new DNA into and between bacteria occur

Answer 7

• transformation
• conjugation
• transduction recombination

Question 8

DNA already in the bacteria move about via which methods

Answer 8

• transposition
• recombination

Question 9

what is transformation

Answer 9

• the uptake of naked DNA
• DNA contacts the bacteria and is taken up
• some bacterial are naturally competent and can take up DNA without treatment which others require lab assistance
• once naked DNA is take into cell there are 2 options: degredation by nucleases or recombination into the genome

Question 10

what is conjugation

Answer 10

• the transfer of genetic material between bacteria through direct cell-to-cell contact
• conjugation is horizontal gene transfer
• it if the transfer of genetic information from a donor cell to a recipient
• for conjugation the donor must host a conjugative or mobilisable genetic element (plasmid or transposon)
• most conjugative plasmids have systems ensuring that the recipient cell does not already contain a similar element

Question 11

what is the clinical relevence of conjugation

Answer 11

the transfer of plasmids can move whole blocks of properties
- antibiotic resistance
- toxins
- virulence properties

Question 12

what is transduction

Answer 12

injection of genome into bacteria by bacteriophage

Question 13

explain the process of generalised transduction by lytic bacteriophage

Answer 13

1. attachment
2. infection/injection of nucleic acid
3. lag phase as things replicate
4. lysis

Question 14

outline the process of specialised transduction

Answer 14

1. lysogen formed
2. bacterial replication with integrated phase
3. induction
4. transducrion. infection with a phage with bacterial DNA, integration of new DNA

Question 15

what is homologous recombination

Answer 15

where 2 DNA sequences are the same they can intercalate their strands. during replication these can get spliced

Question 16

what is non-homologous recombination

Answer 16

less efficient NA does not match but can be in random positions

Question 17

what is directed recombination

Answer 17

insertion elements have repeats which lead to homologous/directed insertions in specific sotes or enzymes that direct integration at set sites.

Question 18

what is DNA restriction

Answer 18

• it is not good for bacteria to constantly take up DNA so they have a restriction system
• they have restriction endonuclease
• which degrade DNA not made in their own cell
• these restriction nucleases do not degrade self-DNA as they act on specific sites
• a bacteria methylates its own DNA where its own restriction nuclease cut so blocking the enzyme
• works on any DNA including non-self plasmids

Question 19

what is transposition

Answer 19

• transposons are sequences of DNA that can move around to different positions within the genome
• transposons encode their own transposases
• the transposae cut and re-insert the DNA flanked by inverted repeats
• the process directed by these enzymes is transposition
• they pop into and out of DNA
• if they insert into a gene they will disrupt it
• they can carry other genes