Biotechnology MCQ Quiz - Objective Question with Answer for Biotechnology - Download Free PDF

The correct answer is Nucleus.

Key Points

• The nucleus is a membrane-bound organelle found in eukaryotic cells.
• It is considered the control center of the cell, as it regulates gene expression and mediates the replication of DNA during the cell cycle.
• The nucleus contains the cell's genetic material (DNA), which is organized into chromosomes.
• It is surrounded by a double membrane called the nuclear envelope, which contains pores for the exchange of substances with the cytoplasm.
• The nucleolus, found within the nucleus, is responsible for ribosome synthesis.

Additional Information

• Cell Membrane:
  • The cell membrane is a semipermeable structure that encloses the cell, protecting it from its external environment.
  • It is composed of a phospholipid bilayer and proteins, which facilitate transport and communication.
• Cytoplasm:
  • The cytoplasm is the gel-like substance found inside the cell membrane but outside the nucleus.
  • It houses organelles and is the site for many biochemical processes.
• Stomata:
  • Stomata are pores found on the surface of leaves and stems, not related to the cell nucleus.
  • They regulate gas exchange and water evaporation in plants.
• Prokaryotic vs. Eukaryotic Cells:
  • Prokaryotic cells lack a nucleus; their genetic material is found in the cytoplasm.
  • Eukaryotic cells have a well-defined nucleus enclosed by a nuclear membrane.

The correct answer is: (A)-(III), (B)-(II), (C)-(IV), (D)-(I).

Explanation:

• (A) Negatively charged amino acid - (III) Aspartate: Aspartate (also known as aspartic acid) has a negatively charged side chain at physiological pH due to the carboxyl group.

• (B) Polar uncharged amino acid - (II) Cysteine: Cysteine has a polar, uncharged side chain due to the thiol (-SH) group. While it can form disulfide bonds, which are important for protein structure, the free thiol group itself is polar and uncharged.

• (C) Aromatic amino acid - (IV) Phenylalanine: Phenylalanine has a large, hydrophobic aromatic ring in its side chain.

• (D) Positively charged amino acid - (I) Histidine: Histidine has a positively charged side chain at physiological pH due to the imidazole group.

NOTE: As the exam question lacked a correct option, we provided the correct solution.

The Correct Answer is : Both (A) and (R) are true and (R) is the correct explanation of (A) 

Explanation:

• Assertion (A): Site-directed mutagenesis is a technique used to alter specific amino acids in a protein by changing the DNA sequence of a cloned gene. This allows researchers to study the structure and function of proteins by introducing specific mutations. ✅ True

• Reason (R): If restriction sites required for traditional mutagenesis are absent, oligonucleotide-directed mutagenesis is used. This method employs synthetic oligonucleotides with the desired mutation to introduce a precise change in the DNA sequence. ✅ True

Since oligonucleotide-directed mutagenesis is a technique that facilitates site-directed mutagenesis when restriction sites are unavailable, (R) correctly explains (A).

The correct answer is: Statement I is false but Statement II is true.

Explanation:

• Statement I is false: While auxins are used to prevent fruit and leaf drop (abscission), that is not their only commercial use. They are used for a variety of other purposes, including:

  • Promoting rooting in cuttings
  • Controlling weed growth (as in some herbicides)
  • Inducing flowering in some plants
  • Fruit thinning

• Statement II is true: Auxins can induce parthenocarpy, which is the development of fruit without fertilization. This results in seedless fruit. This is commercially valuable in crops like grapes, tomatoes, and some citrus fruits.

The correct answer is Nucleus.

Key Points

• The nucleus is a membrane-bound organelle found in eukaryotic cells.
• It is considered the control center of the cell, as it regulates gene expression and mediates the replication of DNA during the cell cycle.
• The nucleus contains the cell's genetic material (DNA), which is organized into chromosomes.
• It is surrounded by a double membrane called the nuclear envelope, which contains pores for the exchange of substances with the cytoplasm.
• The nucleolus, found within the nucleus, is responsible for ribosome synthesis.

Additional Information

• Cell Membrane:
  • The cell membrane is a semipermeable structure that encloses the cell, protecting it from its external environment.
  • It is composed of a phospholipid bilayer and proteins, which facilitate transport and communication.
• Cytoplasm:
  • The cytoplasm is the gel-like substance found inside the cell membrane but outside the nucleus.
  • It houses organelles and is the site for many biochemical processes.
• Stomata:
  • Stomata are pores found on the surface of leaves and stems, not related to the cell nucleus.
  • They regulate gas exchange and water evaporation in plants.
• Prokaryotic vs. Eukaryotic Cells:
  • Prokaryotic cells lack a nucleus; their genetic material is found in the cytoplasm.
  • Eukaryotic cells have a well-defined nucleus enclosed by a nuclear membrane.

The correct option is: 1 

Explanation:

• Circular DNA is characteristic of prokaryotic cells, such as bacteria and archaea, and it exists as a single, circular chromosome located in the nucleoid region. Unlike eukaryotes, prokaryotic DNA is not enclosed within a membrane-bound nucleus and lacks the complex structure of chromatin.
• In contrast, eukaryotic cells have linear DNA contained within a membrane-bound nucleus, organized with histones into chromatin, and usually possess multiple chromosomes.
• Nucleus: A defining feature of eukaryotic cells, the nucleus is a membrane-bound organelle that houses the cell’s genetic material (DNA). Prokaryotic cells lack a true nucleus; instead, their DNA resides in a nucleoid region without a surrounding membrane.
• Membrane-bound organelles: Eukaryotic cells contain various membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum, Golgi apparatus) that perform specialized functions. Prokaryotic cells lack these organelles, with all cellular processes occurring within the cytoplasm or at the cell membrane.
• Histones: Histones are proteins found in eukaryotic cells that package and organize DNA into chromatin. Prokaryotic cells generally lack histones, though some archaea contain histone-like proteins for DNA organization.

The correct answer is Quinine

Concept:

• Medicines derived from plant sources have been used for centuries in traditional and modern medical practices.
• The bark of certain plants contains potent compounds that can be used to treat various illnesses.
• One of the most notable examples is the bark of the Cinchona tree, which is the source of quinine, a medication used to treat malaria.

Explanation:

• Cinchona: The bark of the Cinchona tree contains quinine, an alkaloid used to treat malaria. Quinine has been used for centuries and was one of the first effective treatments for malaria. The Cinchona tree is native to the Andean forests of South America.
• Ephedrine: This is an alkaloid derived from the Ephedra plant, not from the bark but typically from the stems and branches. It is used as a medication and stimulant, often in treating asthma and nasal congestion.
• Alloy: This is not a medicine but a mixture of metals or a mixture of a metal and another element. It is used in various industrial and technological applications.
• Gold: While gold has some medical applications, such as in dentistry and certain treatments for arthritis, it is not derived from plant bark. Gold is a chemical element and a precious metal.

The correct answer is: Gold

Explanation:

• Gold is commonly used in the gene gun method for DNA delivery. The gold microparticles are coated with DNA and then shot into cells at high velocity, typically using helium pressure. Gold is favored because it is biologically inert, non-toxic, and has excellent properties for carrying DNA into cells without causing significant damage.
• Silver:
  • Silver is also a metal, but it is not typically used in gene gun technology. While silver nanoparticles have applications in medicine and antimicrobial treatments, they are not as commonly used for DNA delivery as gold due to potential toxicity issues and less optimal properties for gene gun applications.
• Copper:
  • Copper is another metal, but it is not used for microparticle creation in gene gun methods. Copper tends to be more reactive compared to gold and could potentially interact with biological molecules in a harmful way. This makes it less suitable for applications involving gene delivery.
• Titanium:
  • Titanium is a strong, lightweight metal often used in medical implants and other structural applications due to its biocompatibility. However, it is not typically used for DNA delivery in gene gun methods. Titanium’s properties make it less ideal for creating the fine microparticles needed for efficient DNA transfer compared to gold.

The correct option is: 2

Explanation:

• Unsaturated fatty acids are more abundant in the cell membranes of plants living in colder environments. These fatty acids have one or more double bonds, which create kinks in their structure and prevent the fatty acid chains from packing tightly together. This loose packing maintains membrane fluidity even at lower temperatures, allowing essential cellular processes to continue efficiently. Plants adapt to cold by increasing unsaturated fatty acid content, which helps the membrane remain flexible rather than becoming rigid or brittle.
• Saturated fatty acids: Saturated fatty acids lack double bonds, allowing them to pack closely together, which makes membranes more rigid. High concentrations of these fatty acids are more common in organisms or tissues that do not require high membrane fluidity.
• Long-chain fatty acids: Long-chain fatty acids can reduce membrane fluidity due to their extended structure, which favors close packing. These are typically found in warmer environments where membrane rigidity is beneficial.
• Trans fatty acids: Trans fatty acids, with their trans configuration, also allow tighter packing and can reduce membrane fluidity. They are generally not produced in significant amounts in natural plant membranes.

The correct option is: 4 

Explanation:

• Presence of plasmids: Plasmids are small, circular, extrachromosomal DNA molecules most commonly found in prokaryotic cells. While plasmids are rare in eukaryotes, they are not a defining feature of eukaryotic cells and thus do not align with their typical characteristics.
• The other options correctly describe eukaryotic cell characteristics:
  • Membrane-bound organelles: Eukaryotic cells contain specialized structures called organelles, each enclosed by a membrane and performing distinct functions. Examples include mitochondria (for ATP production), the endoplasmic reticulum (for protein and lipid synthesis), and lysosomes (for intracellular digestion). These organelles are essential for compartmentalizing cellular processes, a feature absent in prokaryotic cells.
  • Linear DNA: Eukaryotes have linear DNA molecules organized into chromosomes within the nucleus. This DNA is associated with histone proteins, forming chromatin, which helps in efficiently packaging DNA and regulating gene expression. This complex structure is essential for eukaryotic cell division and gene regulation.
  • Nucleus: A defining feature of eukaryotic cells, the nucleus is a membrane-bound structure that protects and organizes the cell’s genetic material. The nuclear membrane encloses the DNA, separating it from the cytoplasm and allowing for controlled gene expression and DNA replication.

The correct option is: 2

Explanation:

• Ribosomes are primarily involved in protein synthesis, not lipid synthesis. Ribosomes facilitate the translation of mRNA into polypeptide chains, which then fold to form functional proteins.
• Lipid synthesis occurs in the smooth endoplasmic reticulum (ER), particularly in eukaryotic cells, where lipids and steroids are produced and modified.
• The remaining options accurately match each organelle with its function:
  • Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or use within the cell.
  • Lysosomes contain enzymes that break down macromolecules, aiding in intracellular digestion and recycling of cellular components.
  • Mitochondria are responsible for ATP production through cellular respiration, providing energy for the cell’s metabolic activities.

• Alanine aminotransferase (ALT) is an enzyme found primarily in the liver. When liver cells are damaged, ALT is released into the bloodstream. Hence, elevated levels of ALT are a strong indicator of liver cell damage.
• ALT is more specific to the liver compared to other enzymes, meaning that it is primarily found in the liver and its elevation is more directly related to liver damage or liver disease.
• Monitoring ALT levels is crucial in diagnosing liver conditions such as hepatitis, cirrhosis, and liver toxicity due to medications or other harmful substances.

• Rationale: ALP is an enzyme found in many tissues throughout the body, including the liver, bones, kidneys, and bile ducts. Elevated ALP levels can indicate liver disease, but they are not as specific to liver cell damage as ALT because they can also be elevated in bone disorders and other conditions.

• Rationale: GGT is an enzyme found in the liver, bile ducts, and pancreas. While elevated GGT levels can indicate liver disease, it is not as specific as ALT. GGT can also be elevated in cases of alcohol consumption, pancreatic disease, and other conditions.

• Rationale: AST is an enzyme found in the liver, heart, muscles, and other tissues. Elevated AST levels can indicate liver damage, but since AST is also found in other tissues, it is not as specific as ALT for liver-related issues. Elevated AST can also be seen in muscle injuries and heart attacks.

• Among the given options, Alanine aminotransferase (ALT) is the enzyme most specific to liver cell damage. It is primarily located in the liver and its elevation is a strong indicator of liver health issues, making it a critical marker for diagnosing liver diseases.

The Correct Answer is: 2

Explanation:

• Lymphoid stem cells in the bone marrow are a part of the hematopoietic stem cell lineage, which gives rise specifically to cells of the lymphoid lineage, including:

  • Natural killer cells (NK cells): A type of innate immune cell that kills virus-infected and tumor cells.
  • B lymphocytes (B cells): Adaptive immune cells responsible for producing antibodies.

• Other cells such as platelets and neutrophils arise from myeloid stem cells, not lymphoid stem cells:

  • Platelets: Formed from megakaryocytes, derived from the myeloid lineage.
  • Neutrophils: A type of granulocyte also derived from the myeloid lineage.
• Lymphoid stem cells also differentiate into T lymphocytes (T cells), which mature in the thymus.
• Myeloid stem cells give rise to red blood cells, granulocytes (neutrophils, eosinophils, basophils), monocytes/macrophages, and platelets.

Key Points

• Lymphoid Lineage:

  • Lymphoid stem cells differentiate into three main types of cells:
    • B cells: Responsible for humoral immunity by producing antibodies.
    • T cells: Involved in cell-mediated immunity.
    • Natural Killer (NK) cells: Play a role in innate immunity, attacking virus-infected or tumor cells without prior sensitization.

• Bone Marrow and Lymphoid Organs:

  • Lymphoid stem cells originate in the bone marrow, but further differentiation and maturation of some lymphocytes occur in primary lymphoid organs like the thymus (for T cells).

• Secondary Lymphoid Organs:

  • After maturation, lymphocytes migrate to secondary lymphoid organs such as the spleen, lymph nodes, and MALT (Mucosa-Associated Lymphoid Tissue), where they become activated upon encountering antigens.

• Role in Immunity:

  • B cells: After activation, differentiate into plasma cells that secrete antibodies.
  • T cells: Subtypes include Helper T cells (CD4+) and Cytotoxic T cells (CD8+), which coordinate immune responses or kill infected cells, respectively.

• Difference from Myeloid Stem Cells:

  • Lymphoid stem cells form cells primarily for adaptive immunity (except NK cells).
  • Myeloid stem cells contribute to innate immunity (e.g., neutrophils, macrophages) and other physiological functions like blood clotting (platelets).

The correct answer is: 4

Explanation:

• (A) Yellow fever: Caused by the Yellow fever virus, which is transmitted by mosquitoes (primarily Aedes aegypti).
• (B) Hepatitis B: Caused by the Hepatitis B virus (HBV), which affects the liver.
• (C) Chickenpox: Caused by the Varicella-zoster virus (VZV), which is highly contagious.
• (D) Rabies: Caused by the Rabies virus, which is typically transmitted through bites or scratches from infected animals.