Week 9 - Bacterial Genetics

Question 1

What is the basic structure of the bacterial chromosome?

Answer 1

Single circular molecule of double stranded DNA (dsDNA)

The chromosome is localized in the cytoplasm and anchored to the cytoplasmic membrane.

Question 2

What does the term ‘genome’ refer to in bacteria?

Answer 2

The entire genetic content of an organism, including extrachromosomal elements like plasmids.

Question 3

What are plasmids?

Answer 3

Small, circular extrachromosomal DNA that provides additional advantages such as antibiotic resistance

Question 4

What is bacterial conjugation?

Answer 4

The process where plasmid exchange occurs between two competent bacterial cells.

Question 5

What is the F plasmid?

Answer 5

A fertility factor which directs dna transfer to another bacteria via conjugation

Question 6

What is rolling circle replication?

Answer 6

A process where the F plasmid makes a single-stranded copy of itself that passes into the recipient cell.

Question 7

What are Hfr strains?

Answer 7

Formed when f plasmid integrates into the chromosome, enabling high-frequency recombination

Question 8

What is homologous recombination?

Answer 8

The exchange of DNA sequences between different DNA molecules through highly similar sequences.

Question 9

What role does RecA play in bacterial genetics?

Answer 9

Helps exchange genetic material between homologous DNA sequences and helps repair DNA

Question 10

What are Holliday junctions?

Answer 10

Structures formed during homologous recombination where sequences on donor and recipient DNA are aligned and swapped.

Question 11

What are R plasmids?

Answer 11

Vectors capable of carrying multiple antibiotic resistance genes.

Question 12

What is transformation in bacteria?

Answer 12

The process where bacteria uptake fragments of DNA from the environment and incorporate it into their genome.

Question 13

Who first observed transformation, and in what organism?

Answer 13

Prof Frederick Griffith observed transformation in Streptococcus pneumoniae.

Question 14

What are bacteriophages?

Answer 14

Viruses that infect bacteria, consisting of nucleic acid surrounded by a coat of protein.

Question 15

What is transduction?

Answer 15

DNA transfer mediated by bacteriophages

Question 16

What are the two types of phage life cycles?

Answer 16

• Virulent phages
• Temperate (lysogenic) phages

Question 17

What is generalized transduction?

Answer 17

Any bacterial gene can be transferred

Question 18

What is specialized transduction?

Answer 18

A process where phages can only carry specific parts of the bacterial genome.

Question 19

What is the purpose of mobile genetic elements?

Answer 19

To introduce new genes into a bacterial genome and mediate horizontal gene transfer.

Question 20

What is the difference between vertical and horizontal gene transfer?

Answer 20

Vertical gene transfer occurs through reproduction, while horizontal gene transfer involves the exchange of genetic material between organisms.

Question 21

What is the significance of mosaic structures in bacterial genomes?

Answer 21

Bacterial genomes evolve rapidly by integrating new genetic material from different sources.

Question 22

What are mobile genetic elements?

Answer 22

Mobile genetic elements move genetic material between cells and mediate Horizontal Gene Transfer

Examples include plasmids and bacteriophages.

Question 23

What is the difference between vertical and horizontal gene transfer?

Answer 23

Vertical gene transfer is the transmission of genetic material from parent to offspring, while horizontal gene transfer is the transfer of genetic material between organisms of the same generation.

Question 24

How do bacterial genomes evolve?

Answer 24

Bacterial genomes evolve rapidly, with many species readily taking up and integrating new sections of genetic material into their chromosomes.

Question 25

What is the structure of many bacterial genomes?

Answer 25

Many bacterial genomes are mosaic in structure, consisting of a mix of DNA segments acquired from different sources at various times.

Question 26

Which bacterial species are highly clonal with limited DNA exchange?

Answer 26

Staphylococcus aureus and Mycobacterium tuberculosis are examples of species that are highly clonal.

Question 27

What are genomic islands?

Answer 27

Genomic islands are newly acquired regions of DNA in bacterial genomes that often encode new traits providing a fitness advantage.

Question 28

How is G+C content defined?

Answer 28

G+C content is the ratio of GC bases to AT bases in the genome.

Question 29

What is the G+C content of Mycobacterium tuberculosis and Escherichia coli?

Answer 29

Mycobacterium tuberculosis has a G+C content of 66%, while Escherichia coli has a G+C content of 51%.

Question 30

What are pathogenicity islands?

Answer 30

Pathogenicity islands are genomic islands involved in pathogenicity.

Question 31

What distinguishes commensal E. coli K12 from pathogenic E. coli O157?

Answer 31

E. coli O157 has acquired a virulent phenotype through genomic islands compared to E. coli K12.

Question 32

What does the outer circle in the genome comparison of E. coli K12 and E. coli O157 represent?

Answer 32

The outer circle shows areas of difference and similarity between the genomes of the two strains.

Question 33

What does a G+C content of 50% indicate?

Answer 33

A G+C content of 50% indicates equal proportions of AT and GC bases.

Question 34

What are the three processes by which bacteria can acquire new DNA?

Answer 34

The three processes are recombination, transformation, and transduction.

Question 35

What is transformation in bacteria?

Answer 35

Transformation is the direct uptake of ‘free’ DNA from the external environment.

Question 36

What is transduction in bacteria?

Answer 36

Transduction is the transference of DNA molecules via bacteriophages.

Question 37

What is conjugation in bacterial genetics?

Answer 37

Conjugation involves close contact between bacterial cells, often mediated by F plasmids.

Question 38

What role do mobile genetic elements play in bacterial evolution?

Answer 38

Mobile genetic elements can transfer genes between bacterial species by horizontal gene transfer events.