Biological Techniques MCQs ||| ZOO101 MCQs ||| Set 3

MCQs (Multiple Choice Questions )

1)   Sanger sequencing have ________ basic steps?

    a)        Two

    b)        Four

    c)        Three

    d)        Five

Correct Answer:

The correct answer is  'b'.

Explanation:

Sanger sequencing is a method of DNA sequencing that involves determining the order of nucleotides (adenine, thymine, cytosine, and guanine) in a DNA molecule. The sequencing process includes the following four basic steps:

1. Denaturation: The DNA double strand is heated to separate it into two single strands. This step breaks the hydrogen bonds between complementary nucleotides, resulting in two single-stranded DNA molecules.
2. Primer Annealing: Short DNA sequences called primers are added to the single-stranded DNA. These primers are complementary to regions on the DNA template and provide a starting point for DNA synthesis.
3. DNA Synthesis: DNA polymerase enzyme extends the primers by adding complementary nucleotides to the template DNA strand. Special chain-terminating nucleotides, labeled with fluorescent markers, are also included in the reaction mixture. As the DNA synthesis proceeds, these chain terminators are randomly incorporated, causing the synthesis to stop at different points along the DNA strands.
4. Electrophoresis and Detection: The newly synthesized DNA fragments, with varying lengths due to the incorporation of chain-terminating nucleotides, are separated by size using electrophoresis. The fragments are then detected based on the fluorescence of the chain terminators, and their sequence is determined by the order in which they migrate.

By analyzing the pattern of terminated fragments, scientists can determine the sequence of the original DNA template. This method played a crucial role in early DNA sequencing efforts and remains a valuable tool in molecular biology and genetic research.

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2) Sanger sequencing involves making many copies of a target DNA region by _______.

    a)        Polymerase

    b)        SNVs 

    c)        in vivo

    d)        in vitro

Correct Answer: 

The correct answer is  'a'.

Explanation:

Sanger sequencing involves making many copies of a target DNA region through a process known as DNA synthesis. In this context, DNA polymerase is the enzyme responsible for synthesizing the new DNA strand. During Sanger sequencing, a mixture of DNA polymerase, DNA template, primers, and chain-terminating nucleotides is used.

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3)  Sanger sequencing method first commercialized applied biosystem in _____.

    a)        1978

    b)        1986

    c)        1979

    d)        1981

Correct Answer:  

The correct answer is  'b'.

Explanation:

Applied Biosystems, now part of Thermo Fisher Scientific, introduced the first commercially available automated DNA sequencer, the Applied Biosystems 370A, in 1986. This automated sequencer was based on the Sanger sequencing method and represented a significant advancement in DNA sequencing technology.

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4) PCR was invented in  ________.

    a)        1992

    b)        1883

    c)        1893

    d)        1983

Correct Answer: 

The correct answer is  'd'.

Explanation:

Polymerase Chain Reaction (PCR) was invented by Kary Mullis in 1983. Mullis, an American biochemist, developed the PCR technique while working at Cetus Corporation, a biotechnology company. PCR has since become a fundamental and widely used method in molecular biology and genetics for the amplification of DNA, enabling researchers to make multiple copies of a specific DNA segment for various applications such as DNA sequencing, gene cloning, and diagnostics. The invention of PCR has had a profound impact on the field of molecular biology and has revolutionized many aspects of scientific research and medical diagnostics.

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5)  Denaturation of two strands of DNA occurs at ________

    a)        `92-98^o`C

    b)        `94-97^o`C

    c)        `94-98^o`C

    d)        `94-95^o`C

Correct Answer: 

The correct answer is  'c'.

Explanation:

The temperature range for denaturation is typically 94-98°C. Within this temperature range, the hydrogen bonds between the complementary base pairs (adenine with thymine, and guanine with cytosine) are disrupted, causing the DNA double helix to unwind and the two strands to separate.

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6)  Who invented the PCR?

    a)        Kary Mullis

    b)        Gregor Mendel

    c)        Wilhelm Johannsen

    d)        Theodor Schwann

Correct Answer: 

The correct answer is  'a'.

Explanation:

Kary Mullis is credited with inventing the Polymerase Chain Reaction (PCR). He developed this revolutionary technique in 1983 while working at Cetus Corporation, a biotechnology company. PCR is a method used to amplify and make multiple copies of a specific DNA sequence. Mullis's invention of PCR had a profound impact on molecular biology and genetics, providing a powerful tool for various applications such as DNA sequencing, genetic testing, and molecular diagnostics.

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7)   Taq polymerase, an enzyme oriiginally isolated from_____________

    a)        Campylobacter coli

    b)        Thermus aquaticus

    c)        Borrelia afzelii

    d)        Campylobacter jejuni

Correct Answer: 

The correct answer is  'b'.

Explanation:

Taq polymerase is an enzyme that was originally isolated from the bacterium Thermus aquaticus. The bacterium Thermus aquaticus is a thermophilic bacterium, meaning it thrives in high-temperature environments, such as hot springs. The enzyme Taq polymerase is known for its ability to withstand the high temperatures required for DNA denaturation during the polymerase chain reaction (PCR).

PCR is a widely used molecular biology technique for amplifying DNA. During PCR, the DNA strands need to be denatured, a process that involves heating the reaction mixture to a high temperature. Taq polymerase, being derived from a thermophilic bacterium, remains stable and active at these elevated temperatures. This property makes Taq polymerase especially valuable for PCR applications, as it eliminates the need to add new enzyme after each round of denaturation.

The discovery and use of Taq polymerase have been instrumental in the widespread adoption of PCR technology in various fields, including genetics, forensics, and medical diagnostics.

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8)   Sanger sequencing, also known as the __________________.

    a)        Sequence deletion method

    b)        Chain termination method

    c)        Chain deletion method

    d)        Sequence termination method

Correct Answer: 

The correct answer is  'b'.

Explanation:

Sanger sequencing, also known as the chain termination method, was developed by Frederick Sanger and his colleagues in the late 1970s. The key principle behind Sanger sequencing involves the use of chain-terminating dideoxynucleotides (ddNTPs) along with regular deoxynucleotides (dNTPs) in the DNA synthesis reaction.

In the Sanger sequencing reaction:

1. DNA synthesis occurs in the presence of both normal deoxynucleotides (dNTPs) and chain-terminating dideoxynucleotides (ddNTPs).
2. The chain-terminating ddNTPs lack the 3' hydroxyl group necessary for the formation of a phosphodiester bond with the next nucleotide in the sequence.
3. As a result, when a ddNTP is incorporated into the growing DNA strand, it terminates further elongation.

The reaction produces a set of DNA fragments, each terminating at a specific nucleotide in the sequence. These fragments are then separated by size using gel electrophoresis, and the sequence is determined based on the order of terminated fragments.

Sanger sequencing played a crucial role in the early days of DNA sequencing and was used for the Human Genome Project. While newer sequencing technologies have since been developed, Sanger sequencing remains valuable for certain applications, and its historical significance in DNA sequencing is well-established.

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9)  If we convert `100^o`F into Ceksius scale of temperature, we get _________

    a)        `55.7^o`C

    b)        `40^o`C

    c)        `43.3^o`C

    d)        `60.5^o`C

Correct Answer: 

The correct answer is  'c'.

Explanation:

To convert Fahrenheit to Celsius, you can use the following formula:

Celsius(°C)=(Fahrenheit(°F)−32)× `5/9` 

Now, let's calculate the conversion for 

Celsius=(100−32)× `5/9`​ ≈`37.78^∘`C

So, the correct answer is not among the provided options. The closest option is:

c)  `43.3^∘`C

However, the accurate conversion is approximately `37.78^∘`C.

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10)   PCR methods amplify DNA fragments of _________.

    a)        20 to 30 kilobases

    b)        0.1 to 10 kilobases

    c)        10 to 20 kilobases

    d)        30 to 40 kilobases

Correct Answer: 

The correct answer is  'b'.

Explanation:

The range of DNA fragment sizes that PCR methods can efficiently amplify is largely determined by the choice of DNA polymerase and reaction conditions. The most commonly used DNA polymerase in PCR is Taq polymerase, which is known for its stability at high temperatures. However, it has limitations on the length of DNA fragments it can effectively amplify.

Taq polymerase is most efficient in amplifying DNA fragments up to around 5 kilobases. Beyond this size, the enzyme's processivity and fidelity decrease, making it less suitable for longer fragments. For longer fragments, other DNA polymerases with enhanced processivity and fidelity, such as those derived from thermophilic bacteria or engineered enzymes, may be used.

While the optimal range for Taq polymerase is typically up to 5 kilobases, the inclusion of specific additives, such as certain co-solvents or co-surfactants, may extend the range to approximately 10 kilobases in some cases. However, the efficiency and success of PCR decrease as the fragment size increases.

Therefore, the range mentioned in option b) "0.1 to 10 kilobases" is a generally accepted and practical estimate for the efficient amplification of DNA fragments using standard PCR methods with Taq polymerase.

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