Horizontal gene transfer and mobile elements Flashcards
In addition to acquiring genes via conjugation, transduction, and transformation, natural selection may also favor loss of genes from an organism’s genome. In which of the following bacteria would you most likely expect to find evidence of beneficial genome reduction?
A. aquatic stalked bacterium
B. free-living soil bacterium
C. harmless gut commensal
D. obligate intracellular pathogen
E. opportunistic pathogen
D. obligate intracellular pathogen (has loss the genes that allow it to live outside of a host but this was most likely favoured and evolved from selection)
Which type of DNA uptake is dependent on viruses?
Transduction
Which of the following is not a mechanism by which plasmids ensure their inheritance and maintenance during cell division?
A. low-copy-number plasmids
B. carrying antibiotic resistance genes
C. carrying partitioning system genes, parC, parM, and parR
D. carrying self-preservation genes, known as addiction modules
E. high-copy-number plasmids
low copy number plasmids
While horizontal gene transfer can be beneficial, there are also risks. Bacteria protect themselves from foreign DNA through
restriction endonucleases that cleave unmethylated DNA at specific sites.
Most bacteria contain ________ enzymes that protect the cell from foreign DNA.
restriction
CRISPR uses pieces of phage DNA incorporated into the genome
as the source of an RNA that will guide Cas proteins to cleave the foreign DNA
Many Japanese people consume a diet rich in seaweed, including the edible red alga Porphyra, which is used for preparing sushi. Although humans cannot digest the seaweed polysaccharides (porphyran and agarose), certain marine Bacteroidetes do possess the necessary CAZymes. Curiously, Japanese individuals frequently harbor seaweed-digesting Bacteroides plebeius in their gut microbiomes, while individuals from North America do not. Bacteroides plebeius is not a marine bacterium, and its close relatives cannot digest seaweed. What is the mostly likely explanation for how B. plebeius acquired functional porphyranase and agarase genes?
horizontal transfer of genes from a marine bacterium
Further analyses revealed that a region downstream of the seaweed-digesting genes in Bacteroides plebeius contained sequences homologous to conserved relaxase/mobilization proteins. These data provide additional evidence that the genes were acquired by ________
conjugation
What can function to reshape an organism’s genome
acquisition of genes from other organisms
spontaneous DNA mutations
gene loss by deletion events
gene rearrangement
Which type of DNA uptake is dependent on transferable plasmids?
Conjuguation
Select the true statement regarding the relationship between genotype and phenotype.
A. Only genes that produce proteins are considered part of an organism’s genotype.
B. The phenotype represents the entire genome of an organism.
C. The phenotype reflects only the portion of the genotype that is expressed.
D. Any change in the genotype will be reflected in the phenotype.
E. Some mutations will cause a change in the genotype, while others will not.
The phenotype reflects only the portion of the genotype that is expressed
What event must precede transfer of chromosomal genes by specialized transduction?
site-specific recombination
Over time the genome of a species,
may change due to mutation or gene exchange
What are the 3 mechanisms of horizontal gene transfer in bacteria
conjugation, transduction, transformation
Transposable elements differ from plasmids in that only plasmids
may exist autonomously, not integrated into host DNA
