GRE Subject Test: Biology : Understanding Bacteria

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Bacteria

Which bacterial reproductive process does not involve any genetic recombination?

Possible Answers:

Conjugation

Transduction

Transformation

Binary fission

Correct answer:

Binary fission

Explanation:

Bacteria are capable of reproducing in a variety of ways. Binary fission is most similar to mitosis in animals, and does not involve any genetic recombination. DNA is replicated and passed to identical daughter cells.

In contrast, the other listed methods involve the incorporation of foreign DNA into the bacteria genome. In conjugation, plasmids are exchanged between bacteria via a sex pilus. In transformation the bacterium is capable of incorporating DNA directly from its surrounding environment. In transduction, a bacteriophage vector is used to introduce foreign DNA into the bacterial cell.

Example Question #2 : Understanding Bacteria

Penicillin is a drug that inhibits the formation of peptidoglycan. Based on this mechanism, which infection could be treated using penicillin?

Possible Answers:

Allergic reactions

Fungal infection

Bacterial infection

Viral infection

Correct answer:

Bacterial infection

Explanation:

Peptidoglycan is most well-known for its role in the formation of bacterial cell walls. By inhibiting the production of peptidoglycan, penicillin prevents bacteria from fully developing and is very effective at treating bacterial infections.

Anti-histamines an anti-inflammatory medications can be used to help prevent the autoimmune response that triggers allergic reactions. Fungicides are used to kill fungal infections. Viruses are harder to treat, as they are not technically alive and cannot be "killed."

Example Question #3 : Understanding Bacteria

Which of the following microorganisms are single-celled and reproduce by binary fission?

Possible Answers:

Bacteria

Protozoa

Fungi

Helminths

Viruses

Correct answer:

Bacteria

Explanation:

Bacteria are single-celled organisms that reproduce by binary fission, in which identical copies of the original cell are produced.

Viruses require living cells in order to multiply. The viruses invade cells and redirect the host organelles from their normal functions to instead replicate the virus. Fungi are very different from bactria in that their structure is more complex (eukaryotic) and they reproduce by budding (among other mechanisms). Protozoa include unicellular animal-like microorganisms. Common protozoan infections include malaria and sleeping sickness. Helminths are worm-like animals, including pinworms and tapeworms. 

Example Question #1 : Understanding Bacteria

What is the significance of endospores?

Possible Answers:

They allow fungi to store nutrients that can survive extreme conditions

They are produced by gram-positive bacteria which can survive extreme conditions

They allow fungi to survive in extreme climates

They allow gram-negative bacteria to reproduce

Correct answer:

They are produced by gram-positive bacteria which can survive extreme conditions

Explanation:

Endospores are produced by gram-positive bacteria and can lie dormant for years. Endospores are crucial to growth of gram-positive bacteria because they resist harsh conditions such as extreme temperatures, ultraviolet radiation, and many chemicals. Endospores are not used by fungi by any means. They are also uninvolved in the reproductive processes of bacteria. 

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