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 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 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.

The correct answer is Euphorbiaceae

Concept:

• The Euphorbiaceae family, also known as the spurge family, is characterized by the presence of milky latex in their tissues. This latex is a white, sticky liquid that is exuded when the plant is damaged.
• This family includes a wide variety of plants ranging from small herbs to large trees, and many of these plants are used for medicinal, ornamental, and industrial purposes.
• Some well-known members of the Euphorbiaceae family are the poinsettia (Euphorbia pulcherrima), the rubber tree (Hevea brasiliensis), and the castor oil plant (Ricinus communis).

Explanation:

• Solanaceae: This family, also known as the nightshade family, includes plants such as tomatoes, potatoes, and bell peppers. They do not produce milky latex. The family is known for containing alkaloids, which can be toxic.
• Acanthaceae: This family includes mostly tropical plants such as the shrimp plant (Justicia brandegeeana) and the water willow (Justicia americana). These plants do not produce milky latex and are instead known for their colorful bracts and flowers.
• Capparidaceae: Also known as the caper family, this group includes plants like the caper bush (Capparis spinosa). These plants do not produce milky latex and are often recognized for their edible flower buds and fruits.

The correct option is: 4

Explanation:

• mRNA: Messenger RNA (mRNA) is transcribed in the nucleus and is exported to the cytoplasm, where it serves as a template for protein synthesis during translation.

• rRNA: Ribosomal RNA (rRNA) is also transcribed in the nucleus, specifically in the nucleolus. While rRNA itself is not exported as a complete molecule, it is a component of ribosomes, which are assembled in the nucleolus and then transported to the cytoplasm for protein synthesis. The ribosomal subunits contain rRNA and proteins that are necessary for translation.

• tRNA: Transfer RNA (tRNA) is transcribed in the nucleus and is exported to the cytoplasm. tRNA molecules are responsible for bringing the appropriate amino acids to the ribosome during translation, playing a critical role in protein synthesis.

• All of the above: This statement is correct. All three types of RNA—mRNA, rRNA, and tRNA—are exported from the nucleus to function in protein synthesis. Each type has a distinct role in the process: mRNA serves as the template, rRNA forms the structural and catalytic core of ribosomes, and tRNA brings amino acids to the ribosome.

• The export of these RNAs from the nucleus is a highly regulated process that ensures that the cell has the necessary components for protein synthesis in the cytoplasm. Proper functioning of mRNA, rRNA, and tRNA is essential for cellular activities and overall protein synthesis efficiency.

The correct option is: 2

Explanation:

• It is nonpolar and dissolves easily in lipids: This statement is incorrect. Water is a polar molecule, which means it does not dissolve easily in lipids. Its polarity allows it to dissolve many ionic and polar substances but makes it incompatible with nonpolar substances.

• It accounts for 70% or more of total cell mass and facilitates biochemical reactions: This statement is correct. Water typically makes up 70% or more of the mass of a cell and serves as a solvent for biochemical reactions, facilitating metabolic processes and transporting nutrients and waste products.

• It is used primarily for energy storage in cells: This statement is incorrect. While water is essential for various cellular functions, it is not primarily used for energy storage. Instead, cells store energy in the form of macromolecules like carbohydrates and fats.

• It acts as a structural component of membranes: This statement is incorrect. While water is critical for maintaining cell shape and turgor pressure in plant cells, it does not act as a structural component of membranes. Membranes are primarily composed of lipids and proteins.

• The unique properties of water, such as its high heat capacity, solvent capabilities, and ability to participate in hydrogen bonding, make it vital for sustaining life and enabling cellular functions. Its role in biochemical reactions is crucial for maintaining homeostasis within cells and organisms.

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: 2

Explanation:

• Membrane lipids are not uniformly distributed throughout the membrane. Lipids in the plasma membrane exhibit an asymmetric distribution, with certain types of lipids, like glycolipids, predominantly located on the outer leaflet, while others, such as phosphatidylserine and phosphatidylethanolamine, are mainly found on the inner leaflet.
• The other statements are true:
  • Lipids can flip-flop between the inner and outer leaflets of the bilayer, though this is a rare event as it requires energy due to the hydrophilic head passing through the hydrophobic core. Enzymes like flippases and scramblases facilitate this process.
  • Phospholipids form the bilayer structure of the membrane, with hydrophilic heads facing outward and hydrophobic tails facing inward, creating a semi-permeable barrier.
  • Glycolipids are found on the extracellular surface of the membrane, where they play roles in cell recognition and interaction with the environment.