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NEET MDS Quiz - Practice Test
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Practice Test

General Microbiology - 3 Questions

1
General Microbiology

What is the role of Gene Transfer Agents (GTAs) in horizontal gene transfer?
1) They are viral-like particles that package random pieces of host DNA for transfer between bacteria
2) They facilitate plasmid exchange between bacterial cells
3) They enable DNA uptake from the environment via transformation
4) They allow bacteria to integrate viral DNA into their genome

📝 Explanation:

Correct answer: 2) They facilitate plasmid exchange between bacterial cells

2
General Microbiology

What causes chain termination during Sanger sequencing?
1) Incorporation of dideoxynucleotides (ddNTPs) lacking a 3'-OH group
2) The addition of regular deoxynucleotides (dNTPs) during DNA polymerization
3) A lack of nucleotide triphosphates in the reaction
4) The accumulation of pyrophosphate during elongation

📝 Explanation:

Chain termination in Sanger sequencing is caused by the incorporation of dideoxynucleotides (ddNTPs) lacking a 3'-OH group.

Why ddNTPs Cause Termination

Regular deoxynucleotides (dNTPs) have a 3'-hydroxyl group on the sugar ring.

This 3'-OH group is required to form a bond with the next incoming nucleotide.Dideoxynucleotides (ddNTPs) lack this 3'-OH group and have a 3'-hydrogen instead.

The DNA polymerase adds a ddNTP to the growing chain.

No further nucleotides can attach after a ddNTP is added.

The DNA chain stops growing right there.

3
General Microbiology

Which organism is most commonly used as an indicator of fecal contamination in water?
1) Salmonella
2) Escherichia coli
3) Vibrio cholerae
4) Giardia lamblia

📝 Explanation:

This Gram-negative, rod-shaped bacterium is found abundantly in the intestines of humans and other warm-blooded animals. It is universally accepted by regulatory agencies like the EPA and WHO as the premier fecal indicator bacterium (FIB).

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