Biochemical Techniques Practice Questions

Q: If a biochemical test gives the same reading for a sample on repeated testing, it is inferred that the measurement is -

Precise. ***Precise*** - **Precision** refers to the consistency or **reproducibility** of measurements. If repeated tests yield similar results, the measurement is considered precise. - A precise test may not necessarily be accurate, but it consistently gives the same value, highlighting its **reliability** in producing repeatable results. *Specific* - **Specificity** refers to a test's ability to correctly identify individuals who do **not** have a particular condition (i.e., true negatives). - It measures how well a test avoids **false positives**, indicating that a positive result is truly associated with the target analyte. *Accurate* - **Accuracy** refers to how close a measured value is to the true or **actual value**. - A test is accurate if it provides results that are close to the correct value, not simply if they are consistently the same. *Sensitive* - **Sensitivity** refers to a test's ability to correctly identify individuals who **do** have a particular condition (i.e., true positives). - It measures how well a test avoids **false negatives**, indicating that a negative result truly means the condition is absent.

Q: Isotopes of an element have the same:

Atomic number. ***Atomic number*** - Isotopes are defined as atoms of the same element, meaning they have the same number of **protons**, which determines the atomic number. - The atomic number is unique to each element and dictates its **chemical properties**. - This is the **defining characteristic** that makes isotopes belong to the same element (e.g., C-12, C-13, and C-14 all have 6 protons). *Neutron number* - Isotopes of an element differ in their number of **neutrons**, leading to variations in their mass. - This difference in neutron count is precisely what distinguishes one isotope from another. - For example, C-12 has 6 neutrons while C-14 has 8 neutrons. *Mass number* - The **mass number** is the sum of protons and neutrons in an atom's nucleus. - Since isotopes have different numbers of neutrons, they will also have different mass numbers. - This is why isotopes have different mass designations (C-12 vs C-14). *Electron number* - While neutral atoms of isotopes have the same electron number (equal to the atomic number), this is not always true for **ions**. - Isotopes can gain or lose electrons to form ions with different electron numbers. - The atomic number (protons) remains the **fundamental invariant property** that defines isotopes as belonging to the same element, regardless of ionization state.

Q: Which of the following techniques uses radioisotopes?

RIA. ***RIA*** - **Radioimmunoassay (RIA)** is a highly sensitive immunoassay that uses **radioisotopes** to label antigens or antibodies. - The detection of the labeled component allows for the quantification of substances in very low concentrations, often in biological fluids. *Sequencing of nucleic acid* - **Nucleic acid sequencing** determines the order of nucleotides in DNA or RNA, historically using methods like Sanger sequencing which employed **dideoxynucleotides** labeled with fluorescent dyes, not radioisotopes for routine detection. Modern methods often use next-generation sequencing technologies without radioisotopes. - While early methods for DNA sequencing, such as the original Maxam-Gilbert method, did utilize radioisotopes for labeling DNA fragments, this is not the technique primarily associated with general nucleic acid sequencing today, which has largely moved to fluorescent or semiconductor-based detection. *Mass spectroscopy* - **Mass spectroscopy** works by ionizing samples and measuring the **mass-to-charge ratio** of the ions to identify compounds, not by incorporating radioisotopes. - It is used for identifying unknown compounds, quantifying known compounds, and elucidating the structure and chemical properties of molecules. *ELISA* - **Enzyme-linked immunosorbent assay (ELISA)** uses an **enzyme** conjugated to an antibody or antigen, which then catalyzes a colorimetric or chemiluminescent reaction for detection. - It does not involve the use of radioisotopes for labeling or detection.

Q: Among the biochemical methods of genetic engineering, the Western Blot detects:

Protein. ***Protein*** - **Western blot** (also known as protein immunoblot) is a widely used analytical technique in molecular biology and immunogenetics to detect specific **proteins** in a sample. - It involves separating proteins by size using **gel electrophoresis**, transferring them to a membrane, and then detecting the protein of interest using specific antibodies. *DNA* - **DNA** is typically detected using techniques like **Southern blot** or **PCR (Polymerase Chain Reaction)**. - Western blot is not designed to recognize nucleic acids, but rather uses antibodies that bind to specific protein epitopes. *mRNA* - **mRNA** (messenger RNA) is analyzed using methods like **Northern blot** or **RT-PCR (Reverse Transcription PCR)**. - These techniques specifically target RNA sequences and involve RNA extraction, separation, and hybridization with complementary probes. *RNA* - The general term **RNA** encompasses various types including mRNA, tRNA, and rRNA; Northern blot is the most common method for detecting specific RNA molecules. - Western blot, being an antibody-based assay, is specific for the detection and quantification of **proteins**.

Q: Southern blotting is used for:

DNA. ***DNA*** - **Southern blotting** is a molecular biology technique used to detect specific **DNA sequences** in DNA samples. - It involves **electrophoresis** to separate DNA fragments by size, followed by transfer to a membrane and hybridization with a labeled **DNA probe**. *Protein* - The technique used to detect specific **proteins** is called **Western blotting**, not Southern blotting. - **Western blotting** involves protein separation by **gel electrophoresis**, transfer to a membrane, and detection using specific **antibodies**. *Antibody* - While antibodies are used as probes in techniques like Western blotting, antibodies themselves are not directly analyzed by Southern blotting. - Techniques like ELISA (Enzyme-Linked Immunosorbent Assay) are commonly used to detect and quantify **antibodies** in a sample. *RNA* - The technique used to detect specific **RNA sequences** is called **Northern blotting**. - **Northern blotting** follows a similar principle to Southern blotting but uses **RNA** as the target molecule instead of DNA.

Q: Northern blot is used for the detection of which of the following?

mRNA. ***mRNA*** - **Northern blot** is a laboratory technique used to detect specific **mRNA molecules** among a mixture of RNA. - It involves separating RNA samples by size via **gel electrophoresis**, then transferring them to a membrane and hybridizing with a labeled probe. *Protein DNA interaction* - Techniques like **Chromatin Immunoprecipitation (ChIP)** or **Electrophoretic Mobility Shift Assay (EMSA)** are used to study protein-DNA interactions. - Northern blot does not analyze the binding of proteins to DNA. *DNA* - **Southern blot** is the technique specifically designed for the detection and analysis of specific **DNA sequences**. - It involves electrophoresis of DNA, transfer to a membrane, and hybridization with a DNA probe. *Protein* - **Western blot** is the primary technique used for the detection and analysis of specific **proteins**. - It involves protein electrophoresis, transfer to a membrane, and detection using specific antibodies.

Q: Techniques used for protein expression proteomics study include:

All of the options. ***All of the options*** - All listed techniques—**Polyacrylamide Gel Electrophoresis (PAGE)**, **Gene Expression Analysis**, and **Mass Spectrometry**—are used in protein expression proteomics studies, either directly or indirectly, to analyze and quantify proteins. - The integration of these various techniques provides a comprehensive approach to understanding protein expression profiles. *PolyAcrylamide Gel Electrophoresis (PAGE)* - **PAGE** (including 1D and 2D-PAGE) is a fundamental technique for separating proteins based on their **molecular weight** and **isoelectric point**, which is crucial for visualizing and quantifying expressed proteins. - It often serves as an initial separation step before more detailed analysis, such as **mass spectrometry**. *Gene Expression Analysis (indirectly related to proteomics)* - Although **gene expression analysis** (e.g., using **RT-PCR** or **microarrays**) measures mRNA levels, it is indirectly related to proteomics because mRNA levels often **correlate with protein levels**. - It provides insights into the **transcriptional regulation** that influences protein expression, complementing direct protein analysis. *Mass Spectrometry* - **Mass spectrometry** is a powerful and widely used technique in proteomics for **identifying, quantifying, and characterizing proteins** and peptides by measuring their **mass-to-charge ratio**. - It can be used for both **discovery proteomics** (identifying novel proteins) and **targeted proteomics** (quantifying specific proteins).

Q: FeCl3 test is used in detection of:

Phenol. ***Phenol*** - The ferric chloride (FeCl3) test is used to detect the presence of **phenolic hydroxyl groups** in a compound. - Phenols react with iron(III) ions to form distinctive **colored complexes** (often violet, blue, or green), indicating their presence. *Alcohol* - Alcohols typically do not react with **ferric chloride** to produce a color change. - While some alcohols can be oxidized, the FeCl3 test is not a standard diagnostic tool for alcohols. *Acetic acid* - **Carboxylic acids** like acetic acid do not react with ferric chloride in a way that produces a characteristic color change for identification. - Other tests are used to identify carboxylic acids, such as their **acidity** or reaction with bicarbonates. *Hydrochloric acid* - Hydrochloric acid is a **strong inorganic acid** and does not contain phenolic groups. - It does not react with **ferric chloride** to give a color change that would be used for its diagnosis or identification in this context.

Q: Which of the following is a primarily RNA based technique?

Northern blotting. ***Northern blotting*** - **Northern blotting** is a molecular biology technique used to study **gene expression** by detecting specific **RNA molecules** (mRNA) in a sample. - It involves separating RNA fragments by **gel electrophoresis**, transferring them to a membrane, and then detecting specific sequences using **labeled probes**. *Western blotting* - **Western blotting** is a technique used to detect specific **proteins** in a sample. - It involves separating proteins by **gel electrophoresis**, transferring them to a membrane, and then detecting specific proteins using labeled **antibodies**. *Southern blotting* - **Southern blotting** is a molecular biology method used for the detection of **specific DNA sequences** in DNA samples. - It involves separating **DNA fragments** by **gel electrophoresis**, transferring them to a membrane, and then hybridizing with a labeled probe. *Sanger's technique* - **Sanger sequencing**, or the **dideoxy chain-termination method**, is a widely used method for **DNA sequencing**. - It uses **dideoxynucleotides** to terminate DNA synthesis at specific bases, allowing the determination of the **DNA sequence**.

Q: What is the primary enzyme commonly used in the polymerase chain reaction (PCR) process?

Taq polymerase. ***Taq polymerase*** - This **heat-stable DNA polymerase**, isolated from *Thermus aquaticus*, is the cornerstone of PCR due to its ability to withstand the high temperatures required for DNA denaturation without losing activity. - Its high processivity and thermal stability allow for multiple rounds of DNA amplification, making it ideal for the **thermostable cycles** of PCR. *RNA polymerase* - **RNA polymerase** is primarily involved in **transcription**, synthesizing RNA from a DNA template in gene expression, not DNA amplification. - It lacks the ability to synthesize DNA from a DNA template, which is the core function required for PCR. *Topoisomerase* - **Topoisomerase** enzymes are involved in managing **DNA supercoiling** during replication and transcription by cutting and rejoining DNA strands. - They do not possess the template-dependent DNA synthesis activity necessary for PCR. *DNA polymerase* - While **DNA polymerase** is responsible for DNA synthesis in general (e.g., in DNA replication), typical eukaryotic or prokaryotic DNA polymerases are **heat-labile** and would be denatured during the high-temperature steps of PCR. - The specific requirement for PCR is a **thermostable DNA polymerase**, which is why *Taq* polymerase (a type of DNA polymerase) is preferred.

Question 1

If a biochemical test gives the same reading for a sample on repeated testing, it is inferred that the measurement is -

Accepted Answer

Precise

Answer

Specific

Answer

Accurate

Answer

Sensitive

Question 2

Isotopes of an element have the same:

Accepted Answer

Atomic number

Answer

Neutron number

Answer

Mass number

Answer

Electron number

Question 3

Which of the following techniques uses radioisotopes?

Accepted Answer

RIA

Answer

Sequencing of nucleic acid

Answer

Mass spectroscopy

Answer

ELISA

Question 4

Among the biochemical methods of genetic engineering, the Western Blot detects:

Accepted Answer

Protein

Answer

DNA

Answer

mRNA

Answer

RNA

Question 5

Southern blotting is used for:

Accepted Answer

DNA

Answer

Protein

Answer

Antibody

Answer

RNA

Question 6

Northern blot is used for the detection of which of the following?

Accepted Answer

mRNA

Answer

Protein DNA interaction

Answer

DNA

Answer

Protein

Question 7

Techniques used for protein expression proteomics study include:

Accepted Answer

All of the options

Answer

PolyAcrylamide Gel Electrophoresis (PAGE)

Answer

Gene Expression Analysis (indirectly related to proteomics)

Answer

Mass Spectrometry

Question 8

FeCl3 test is used in detection of:

Accepted Answer

Phenol

Answer

Alcohol

Answer

Acetic acid

Answer

Hydrochloric acid

Question 9

Which of the following is a primarily RNA based technique?

Accepted Answer

Northern blotting

Answer

Western blotting

Answer

Southern blotting

Answer

Sanger's technique

Question 10

What is the primary enzyme commonly used in the polymerase chain reaction (PCR) process?

Accepted Answer

Taq polymerase

Answer

RNA polymerase

Answer

Topoisomerase

Answer

DNA polymerase

Biochemical Techniques — MCQs

Biochemical Techniques — MCQs

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