Lecture 35: Microbial Genetics

Question 1

If there is moisture there’ll be…

Answer 1

• Microorganisms

- They’re evolving all the time

Question 2

The properties of a bacterial genome:

Answer 2

• Mutation
• Transformation
• Transduction
• Conjugation

Question 3

What is Mutation (in terms of bacterial genomes) important for?

Answer 3

• Generating Microbial diversity

Question 4

What occurs during Transformation (in terms of bacterial genomes)?

Answer 4

• Selective uptake of DNA by some bacteria

Question 5

What occurs during Transduction (in terms of bacterial genomes)?

Answer 5

• Exchange of Bacterial DNA by viruses

Question 6

What is a genome?

Answer 6

• The total complement of genetic information of a cell or a virus
• Blend of gene and chromosome

Question 7

What is genomics?

Answer 7

• Study of all the genes of a cell, or tissue, at the DNA (genotype), RNA (transcriptome), or protein (proteome)

Question 8

Was the man-made chromosome made using completely artificial materials?

Answer 8

• No, still needed a living cell

- Artificial template

Question 9

Spores:

Answer 9

• Natures way to preserve genomes

- Lets organisms survive in extreme conditions

Question 10

As you increase the gene complement you increase…

Answer 10

• The chances of growth

Question 11

What occurs during mutation in a bacterial genome?

Answer 11

• Change in single nucleotide (substitution, deletion, addition)
• Occur spontaneously and randomly
• Can be induced (UV, chemicals, etc.)
• DNA –> RNA : low fidelity reaction, viruses have a high chance of mutation
• Tons of strains

Question 12

What occurs during transformation?

Answer 12

• Transfer of genetic information between one organism and another
• Involves the exchange of naked DNA with recipient cells / uptake of DNA
• Horizontal Gene Transfer = not related organisms exchanging genetic info
• Used in Biotechnology: select genes and put them into other organisms (GMO)

Question 13

Griffith’s Transformation Experiment:

Answer 13

• Live cells = dead mouse
• Heat treated dead S strain cells = alive mouse
• Strain R cells (no capsule) = alive mouse
• Living strain R + Heat treated dead cells = dead mouse (there was a capsule)
• Some cells take up DNA from environment and incorporate it into their chromosomes (dead cells)

Question 14

What occurs during transduction?

Answer 14

• (Lytic Cycle)
• Most sophisticated of all virus
• Phage injects its DNA
• Phage enzymes degrade host DNA
• Cell synthesizes new phages that incorporate phage DNA and, mistakenly, some host DNA.
• Transducing phage injects donor DNA
• Donor DNA is incorporated into recipient’s chromosome by recombination
• (Defective Phage)

Question 15

Generalised Transduction:

Answer 15

• Transducting a whole bunch of genes from one cell to another

Question 16

Prophage:

Answer 16

• Lysogenic cycle
• Now hybrid bacteria + viral genes
• Keep replicating itself as long as host cell survives

Question 17

What are plasmids?

Answer 17

• Fertility factors in bacteria for genetic exchange
• Can transfer multiple drug resistance genes (first transport found)
• Influence virulence of bacteria
• Used in biotechnology to replicate and transfer specific genes

Question 18

What is conjugation?

Answer 18

• One pilus attaches to similar organisms
• Two cells are now together
• And now transfer of fertility plasmids

Question 19

High frequency recombinant Cells (Hfr) :

Answer 19

• Transfer multiple bacterial genes
• A fragment of the fertility factor and a little bit of chromosomal DNA transfers across
• Doesn’t make the cell F+
• Recipient cell remains F-