MICROBES BIOL371 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS GRADED A++
Ecosystems are based on _ interactions: evolution of eukaryotes and oxygen in
the atmosphere
microbes
- A lot of underlying ecology is carried out by microbes
- Microorganisms connect macroscopic ecosystems to the physical world
Describe homologous reciprocal recombination
Homologous chromosomes exchange equal segments of genetic material, leading to
genetic variation in the resulting gametes.
Can be in:
- patches
- splices
Three tree-like patterns
1. Charles Darwin's sketch
2. Ribosome rRNA tree: eukaryotes are only the green part of the top fan, bacteria and
archaea are all the rest
3. Artist interpretation of the tree of life
Describe snow-ball earth theory
A theory that the earth has been almost fully frozen at least twice in the history of earth.
- Promoting extinction and then diversity of species
,State the three mechanisms of HGT
1. Conjugation: exchange of genetic material via a pili
2. Transduction: phage mediated genetic exchange
3. Transformation: genetic material is taken up from the environment
Other mechanisms of HGT
- Self-fusion: in response to stress two species fuse and combine their genomes
- Gene transfer agents: uncommon units that transfer genes but are not viruses
Describe a prion
A prion is an infectious misfolded protein, they do not contain genetic information, the
structure alone makes them infectious
- Human brain prion: stick to neurons causing conformational changed in other cells
Describe a plasmid
Self-contained DNA that puts itself into another cell that makes the infected cell capable
of conjugation
Required structures for conjugation
- Donor with conjugation material
- Recipient cell
- A mechanism of cells to join; pili
- Proteins on cell membranes
Mechanisms of HGT:
Conjugation process - image
Mechanisms of HGT:
Conjugation process
,Conjugation tends to be between closely/distantly related species
closely
Conjugation:
Describe transfer proteins
Transfer proteins help formation the pili and guide the plasmid (and other DNA) into the
new cell
Describe recombination
Genetic material that has been transferred to a foreign cell is incorporated into the
genome
Conjugation:
Specific (transfer) proteins required to
- Unravel the plasmid
- Membrane proteins: Copy the plasmid through the pilus
- Inject the plasmid into their recipient cell
Describe conjugated plasmids
Plasmids which carry genes that typically facilitate their own transfer
Conjugated plasmids can/can't integrate into the chromosome
can
When a conjugated plasmid is integrated into the chromosome by
recombination ...
... other genes are often moved with them making it another form of HGT
Mechanisms of HGT:
Describe transduction
, Phages usually infect cells with their own DNA, but they are not selective about what
DNA they pick up. Sometimes they accidentally pick up the victim cells DNA and is form
of HGT
Mechanisms of HGT:
Describe transformation
When DNA from the environment is taken up, the recipient has to have DNA binding
proteins (species specific) on the surface to facilitate this
Transformation:
What are the issues?
Size: DNA is a large molecule so the individual needs to have specific machinery for
this
- Often happens in species that used DNA as food
Time: genetic machinery needs to pick it up before enzymes can break it down
State the facilitators of HGT
1. Plasmids
2. Insertion sequences
3. Transposons
Facilitators of HGT:
Describe plasmids warfare
Plasmids have defenses that protect against other plasmids entering cells and genomes
Facilitators of HGT:
Describe insertion sequences
COMPLETE SOLUTIONS GRADED A++
Ecosystems are based on _ interactions: evolution of eukaryotes and oxygen in
the atmosphere
microbes
- A lot of underlying ecology is carried out by microbes
- Microorganisms connect macroscopic ecosystems to the physical world
Describe homologous reciprocal recombination
Homologous chromosomes exchange equal segments of genetic material, leading to
genetic variation in the resulting gametes.
Can be in:
- patches
- splices
Three tree-like patterns
1. Charles Darwin's sketch
2. Ribosome rRNA tree: eukaryotes are only the green part of the top fan, bacteria and
archaea are all the rest
3. Artist interpretation of the tree of life
Describe snow-ball earth theory
A theory that the earth has been almost fully frozen at least twice in the history of earth.
- Promoting extinction and then diversity of species
,State the three mechanisms of HGT
1. Conjugation: exchange of genetic material via a pili
2. Transduction: phage mediated genetic exchange
3. Transformation: genetic material is taken up from the environment
Other mechanisms of HGT
- Self-fusion: in response to stress two species fuse and combine their genomes
- Gene transfer agents: uncommon units that transfer genes but are not viruses
Describe a prion
A prion is an infectious misfolded protein, they do not contain genetic information, the
structure alone makes them infectious
- Human brain prion: stick to neurons causing conformational changed in other cells
Describe a plasmid
Self-contained DNA that puts itself into another cell that makes the infected cell capable
of conjugation
Required structures for conjugation
- Donor with conjugation material
- Recipient cell
- A mechanism of cells to join; pili
- Proteins on cell membranes
Mechanisms of HGT:
Conjugation process - image
Mechanisms of HGT:
Conjugation process
,Conjugation tends to be between closely/distantly related species
closely
Conjugation:
Describe transfer proteins
Transfer proteins help formation the pili and guide the plasmid (and other DNA) into the
new cell
Describe recombination
Genetic material that has been transferred to a foreign cell is incorporated into the
genome
Conjugation:
Specific (transfer) proteins required to
- Unravel the plasmid
- Membrane proteins: Copy the plasmid through the pilus
- Inject the plasmid into their recipient cell
Describe conjugated plasmids
Plasmids which carry genes that typically facilitate their own transfer
Conjugated plasmids can/can't integrate into the chromosome
can
When a conjugated plasmid is integrated into the chromosome by
recombination ...
... other genes are often moved with them making it another form of HGT
Mechanisms of HGT:
Describe transduction
, Phages usually infect cells with their own DNA, but they are not selective about what
DNA they pick up. Sometimes they accidentally pick up the victim cells DNA and is form
of HGT
Mechanisms of HGT:
Describe transformation
When DNA from the environment is taken up, the recipient has to have DNA binding
proteins (species specific) on the surface to facilitate this
Transformation:
What are the issues?
Size: DNA is a large molecule so the individual needs to have specific machinery for
this
- Often happens in species that used DNA as food
Time: genetic machinery needs to pick it up before enzymes can break it down
State the facilitators of HGT
1. Plasmids
2. Insertion sequences
3. Transposons
Facilitators of HGT:
Describe plasmids warfare
Plasmids have defenses that protect against other plasmids entering cells and genomes
Facilitators of HGT:
Describe insertion sequences
