GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Prokaryotic Genome
Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology
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Example Questions
Example Question #1 : Prokaryotic Genome
Which comparisons between eukaryotic and prokaryotic genomes are true?
Prokaryotic genomes frequently have many transposable elements
Both genomes are replicated in the nucleus
All of these
Eukaryotic genes are often single and not in operons like prokaryotic genes
Both types of genomes have large spacer regions between genes
Eukaryotic genes are often single and not in operons like prokaryotic genes
The only true comparison of those listed is that eukaryotic genes are not often present in operons, like prokaryotes often have (think the frequently studied lac operon). Eukaryotes, not prokaryotes, have many transposable elements (a contributing factor to why our genomes are so large). Prokaryotes do not have large spacer regions between their genes, their genomes are often extremely compact. Prokaryotic cells lack nuclei, thus, DNA replication occurs in the cytosol.
Example Question #1 : Prokaryotic Genome
The Frederick Griffith experiment showed that previously safe pneumococcus can become lethal when it incorporates DNA from the surroundings into its genome.
What type of genetic transfer was displayed in the Frederick Griffiith experiment?
Conjugation
Transformation
Transduction
Binary fission
Transformation
When a bacterium has incorporated DNA from the outside environment into its own genome, the process of transformation has occurred.
Example Question #2 : Prokaryotic Genome
Which type of bacterial genetic recombination involves the use of a viral vector?
Assimilation
Conjugation
Transduction
Transformation
Transduction
Sometimes a bacteriophage can encapsulate host bacterial DNA instead of viral DNA. When this virus infects another bacterium, it will inject the previous bacterium's DNA into the new bacterium. This process is referred to as transduction.
Example Question #1 : Help With Transduction, Conjugation, And Transformation
What plasmid, usually in multiple copies in a prokaryote, is responsible for production of proteins to attack susceptible organisms?
Col plasmids
F plasmids
Virulence plasmids
R plasmids
Degradative plasmids
Col plasmids
The correct answer is the Col plasmid, which produce attack proteins called colicins. These are generally small and in many copies in a prokaryote for efficiency. F plasmids are involved in conjugation, R plasmids in resistance, degradative plasmids in digestion of unusual substances, and virulence plasmids in the conversion of certain bacteria into pathogens.
Example Question #1 : Prokaryotic Genome
What type of phages facilitate specialized transduction?
Lytic phages
Lysogenic phages
Animal viruses
Retroviruses
None of these
Lysogenic phages
Specialized transduction occurs when a prophages excises from the host bacterial genome incorrectly and brings some of the bacterial chromosome with it. This DNA then gets packaged into viral particles along with the viral genome and gets inserted into the next bacterium that virus infects. Since only lysogenic phage can become prophage, specialized transduction can only be mediated by lysogenic phage. Retroviruses are enveloped and thus infect animal cells, not bacterial cells.
Example Question #1 : Help With Transduction, Conjugation, And Transformation
Bacteria are capable of "sharing" genetic material that can be advantageous in certain environments. This type of gene transmission is an example of which of the following?
Fission
Transformation
Transduction
Conjugation
Conjugation
In this example, note that the new genes are being received from a donor bacterium. This is only seen in conjugation events.
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