MIMG 158 Final Exam Questions &
Answers (Grade A+)
Where was it found that tropism switching occurs in the BPP, BIP,
and BMP phage variants? How does this occur? What is the
significance of this for phage-bacterial interactions? -
correct answer ✅Tropism switching occurs in the 3' end of the
major tropism determinant (mtd) gene in all phage variants
Nucleotide substitutions took place within this gene, resulting in
variation in the mtd protein and in its ligand specificity
Occurs through a DGR-mediated mechanism --> specifically
switches nucleotides from the terminal repeat region to the
variable repeat region of the gene
Indicates a mechanism by which the phage is able to adjust its
receptor specificity to adapt to the bacteria's ligand diversification,
allowing the phage to continue to infect the target bacteria
Why is it important that the binding between BPP-1 phage and
associated bacterial receptors is multivalent? -
correct answer ✅Multivalent interactions amplify the overall
binding affinity of two protein groups
,MIMG 158 Final Exam Questions &
Answers (Grade A+)
Provides a wide breadth of binding possibilities
Variations in BPP-1 phage mtd trimers influenced by DGRs often
results in very low-affinity interactions with receptors --> variations
exhibit low specificity
-->Phage requires multivalent interactions between mtd surface
protein and bacterial surface receptor to bind to the cell with
sufficient affinity
How was self-splicing used to determine that DGR homing occurs
through an RNA intermediate? -
correct answer ✅HYPOTHESIS: since RTs and the role of Brt in
tropism is conserved, mutagenic homing must occur through an
RNA intermediate
-->a self-splicing intron from phage T4 was tagged into BPP-1 TR
Intron excisions take place only at the RNA level --> if exon ligation
was detected, then RNA must have been present
,MIMG 158 Final Exam Questions &
Answers (Grade A+)
PCR assays used to detect VR sequences derived from td intron-
tagged TRs
RESULTS: products containing VR sequences and ligated to td exons
--> excision occurred and DGR homing proceeds through an RNA
intermediate
Why were researchers inclined to hypothesize that organisms of the
CPR and DPANN phyla might utilize the DGR mechanism to create
more protein diversification? -
correct answer ✅Previously known:
Organisms within the CPR and DPANN phyla have minimal genomes
along with a lack of complete biosynthetic pathways encoded
within their genomes
By using DGRs, organisms would be able to generate a high level of
genetic diversification, potentially allowing organisms to obtain
some of the genes do not encode for without genetic variation
--> Organisms are able to achieve a level of protein diversification
necessary for survival
, MIMG 158 Final Exam Questions &
Answers (Grade A+)
What were the findings regarding the genes located in close
proximity to the DGR genes, and what do these findings implicate? -
correct answer ✅DGRs in CPR and DPANN organisms were all
within close proximity in the genome to at least one transposase
gene
Transposase gene: encodes a protein necessary for genomic
transpositions --> DGRs potentially undergoing HGT in these phyla
as they are found to be encoded next to genes utilized in HGT
HGT would allow for DGRs to be passed between organisms to
provide selective survival advantages to these organisms.
PHYLOGENETIC ANALYSIS:
DGRs offer advantages and are retained cross a large evolutionary
range
IMPLICATIONS: DGRs are a mechanism by which organisms obtain
survival advantages and are transferred via HGT
T1D and T2D -
correct answer ✅DIABETES
Answers (Grade A+)
Where was it found that tropism switching occurs in the BPP, BIP,
and BMP phage variants? How does this occur? What is the
significance of this for phage-bacterial interactions? -
correct answer ✅Tropism switching occurs in the 3' end of the
major tropism determinant (mtd) gene in all phage variants
Nucleotide substitutions took place within this gene, resulting in
variation in the mtd protein and in its ligand specificity
Occurs through a DGR-mediated mechanism --> specifically
switches nucleotides from the terminal repeat region to the
variable repeat region of the gene
Indicates a mechanism by which the phage is able to adjust its
receptor specificity to adapt to the bacteria's ligand diversification,
allowing the phage to continue to infect the target bacteria
Why is it important that the binding between BPP-1 phage and
associated bacterial receptors is multivalent? -
correct answer ✅Multivalent interactions amplify the overall
binding affinity of two protein groups
,MIMG 158 Final Exam Questions &
Answers (Grade A+)
Provides a wide breadth of binding possibilities
Variations in BPP-1 phage mtd trimers influenced by DGRs often
results in very low-affinity interactions with receptors --> variations
exhibit low specificity
-->Phage requires multivalent interactions between mtd surface
protein and bacterial surface receptor to bind to the cell with
sufficient affinity
How was self-splicing used to determine that DGR homing occurs
through an RNA intermediate? -
correct answer ✅HYPOTHESIS: since RTs and the role of Brt in
tropism is conserved, mutagenic homing must occur through an
RNA intermediate
-->a self-splicing intron from phage T4 was tagged into BPP-1 TR
Intron excisions take place only at the RNA level --> if exon ligation
was detected, then RNA must have been present
,MIMG 158 Final Exam Questions &
Answers (Grade A+)
PCR assays used to detect VR sequences derived from td intron-
tagged TRs
RESULTS: products containing VR sequences and ligated to td exons
--> excision occurred and DGR homing proceeds through an RNA
intermediate
Why were researchers inclined to hypothesize that organisms of the
CPR and DPANN phyla might utilize the DGR mechanism to create
more protein diversification? -
correct answer ✅Previously known:
Organisms within the CPR and DPANN phyla have minimal genomes
along with a lack of complete biosynthetic pathways encoded
within their genomes
By using DGRs, organisms would be able to generate a high level of
genetic diversification, potentially allowing organisms to obtain
some of the genes do not encode for without genetic variation
--> Organisms are able to achieve a level of protein diversification
necessary for survival
, MIMG 158 Final Exam Questions &
Answers (Grade A+)
What were the findings regarding the genes located in close
proximity to the DGR genes, and what do these findings implicate? -
correct answer ✅DGRs in CPR and DPANN organisms were all
within close proximity in the genome to at least one transposase
gene
Transposase gene: encodes a protein necessary for genomic
transpositions --> DGRs potentially undergoing HGT in these phyla
as they are found to be encoded next to genes utilized in HGT
HGT would allow for DGRs to be passed between organisms to
provide selective survival advantages to these organisms.
PHYLOGENETIC ANALYSIS:
DGRs offer advantages and are retained cross a large evolutionary
range
IMPLICATIONS: DGRs are a mechanism by which organisms obtain
survival advantages and are transferred via HGT
T1D and T2D -
correct answer ✅DIABETES
