Life Sciences MCQ Quiz - Objective Question with Answer for Life Sciences - Download Free PDF

Key Points

• Statement I: Diffusion does not require any energy expenditure because it is a passive process where molecules move from a region of higher concentration to a region of lower concentration due to the concentration gradient.
• Statement III: In plants, the transport of materials over longer distances occurs through vascular tissues (xylem and phloem), which is referred to as translocation. This process is essential for the distribution of water, nutrients, and food throughout the plant.
• Both statements I and III are correct, making Option 3 the correct choice.

Additional Information

• Statement II: Facilitated diffusion involves the movement of substances across a membrane with the help of specific transport proteins, but it does not require ATP. It is still a passive process, as substances move along the concentration gradient.
• Statement IV: Facilitated diffusion is highly specific to the molecules being transported. The transport proteins involved are designed to recognize specific molecules or ions, ensuring selective transport.
• Diffusion: Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration without the involvement of energy or specific transport proteins.
• Translocation: The process of translocation in plants involves the movement of food (sugars), minerals, and water through xylem and phloem tissues. This is an active process that can occur over long distances.
• Facilitated Diffusion: Facilitated diffusion is a passive transport mechanism that uses transport proteins to move molecules across the cell membrane. It does not require energy expenditure (ATP) and is specific to certain molecules.

The correct answer is option 2.

In News

• The Sample Registration System (SRS) 2021 Report released by the Registrar-General of India provided key demographic insights on fertility rates and the aging population across Indian States.

Key Points

• Statement 1: The Total Fertility Rate (TFR) is defined as the average number of children born to a woman over her reproductive lifespan. Hence, Statement 1 is correct.
• Statement 2: The SRS 2021 Report states that India’s TFR stands at 2.0, which is below the replacement level fertility rate of 2.1. Hence, Statement 2 is correct.
• Statement 3: Kerala (14.4%), Tamil Nadu (12.9%), and Himachal Pradesh (12.3%) are reported to have the highest percentage of population aged 60 and above. Hence, Statement 3 is correct.
• Statement 4: Bihar (6.9%), Assam (7%), and Delhi (7.1%) are reported to have the lowest, not the highest, percentage of elderly population. Hence, Statement 4 is incorrect.

Additional Information

• Bihar has the highest TFR at 3.0, while Delhi and West Bengal have the lowest at 1.4.
• The report notes a demographic shift with a rising working-age population (15-59 years).
• The mean age at marriage for females has increased from 19.3 years in 1990 to 22.5 years in 2021.
• A high-powered committee was announced in the Union Budget 2024 to address demographic challenges.

The correct answer is Mutualism.

Key Points

• Lichens represent a symbiotic relationship between a fungus and a photosynthetic partner (algae or cyanobacteria).
• In this relationship, both the fungus and the photosynthetic partner benefit mutually.
• The fungus provides a protective structure and absorbs water and nutrients, while the algae or cyanobacteria produce food through photosynthesis.
• Lichens are a classic example of mutualism, where both organisms depend on each other for survival.
• This relationship allows lichens to thrive in extreme environments like deserts, tundras, and even bare rocks.

Additional Information

• Mutualism: A type of symbiotic interaction where both species involved derive benefits, such as the relationship between pollinators and flowering plants.
• Other types of symbiosis:
  • Commensalism: One organism benefits, while the other is neither helped nor harmed (e.g., barnacles on whales).
  • Parasitism: One organism benefits at the expense of the other (e.g., ticks feeding on animals).
  • Amensalism: One species is inhibited or destroyed, while the other remains unaffected (e.g., penicillin killing bacteria).
  • Predation: One organism (predator) kills and eats another organism (prey).
• Lichens are bioindicators of air quality, as they are sensitive to air pollution, especially sulfur dioxide.
• The fungal component of lichens is mostly from the phylum Ascomycota, while the photosynthetic partner is either green algae or cyanobacteria.
• Lichens play an important ecological role by contributing to soil formation and providing food and shelter to various organisms in ecosystems.

The correct answer is Richard Evans Schultes

Explanation: 

• Richard Evans Schultes (1915-2001) is known as the "father of ethnobotany".
• He was an American biologist who studied how indigenous peoples use plants, particularly in the Americas. 

Other Options:

• George Bentham: George Bentham (1800-1884) was a prominent English botanist known for his significant contributions to plant classification and taxonomy. Alongside Sir Joseph Dalton Hooker, he co-authored the influential work "Genera Plantarum," which cataloged numerous plant species and laid the groundwork for modern botanical classifications
• Carolus Linnaeus: Carolus Linnaeus (1707-1778), also known as Carl von Linné, was a Swedish botanist, physician, and zoologist. He is best known for developing the binomial nomenclature system, which is the formal system of naming species of living things. 
• William Withering:  William Withering (1741-1799) was an English botanist, geologist, chemist, and physician. He is best known for his discovery of the medical use of Digitalis purpurea (foxglove) in treating heart conditions. 

The correct answer is Trifolium repens.

Key Points

• Trifolium repens, commonly known as white clover, is a perennial herbaceous plant in the Fabaceae family.
• It is widely used as fodder for livestock due to its high protein content and palatability.
• White clover is also used as a leafy vegetable in some cultures and is rich in nutrients.
• It plays a significant role in nitrogen fixation, enhancing soil fertility through symbiotic relationships with Rhizobium bacteria.

Additional Information

• Crotalaria juncea
  • Also known as sunn hemp, it is mainly used as a green manure and cover crop.
  • It is not commonly used as fodder or a leafy vegetable for human consumption.
• Gloriosa superba
  • Known as flame lily, it is a highly toxic plant and is primarily used for medicinal purposes in traditional medicine.
  • It is not used as fodder or a leafy vegetable.
• Asparagus officinalis
  • ​Commonly known as asparagus, it is a perennial flowering plant species used as a vegetable.
  • However, it does not belong to the Fabaceae family.

The correct answer is Option 4 i.e.Nus A is necessary for intrinsic transcription termination.

Concept:

• Bacterial transcription termination serves two important purposes:
  • regulation of gene expression
  • recycling of RNA polymerase (RNAP)
• Bacteria have 2 major modes of termination of bacterial RNA polymerase (RNAP):
  • Intrinsic (Rho-independent)
  • Rho-dependent

Intrinsic Termination - 

• Intrinsic termination occurs by the specific sequences present in the mRNA sequence itself. 
• These RNA sequences form a stable secondary hairpin loop-type structure signaling for termination. 
• The base-paired region called the stable 'stem' consists of 8-9 'G' and 'C' rich sequences.
• The stem is followed by 6-8 ‘U’ rich sequences.
• Intrinsic transcription terminators consist of an RNA hairpin followed by Uridine-rich nucleotide sequences.
• Intrinsic termination needs two major interactions: 1) nucleic acid elements with 2) RNAP.
• Additional interacting factors like Nus A, could enhance the efficiency of termination but not necessary for intrinsic termination.

Rho-dependent Termination - 

• Rho-dependent termination on the other hand requires Rho protein which is an ATP-dependent RNA hexamer translocase (or helicase). 
• Rho protein binds with ribosome-free mRNA and 'C' rich sites on the mRNA (Rut site).

Explanation:

Option 1: Some terminator sequences require Rho protein for termination

• Since Rho protein is required for termination this option is correct. 

Option 2: Inverted repeat and ‘T’ rich non‐ template strand define intrinsic terminators.

• The image given below represents a pre-requisite template for the intrinsic terminator.
• We can find a T-rich sequence on the non-template DNA strand.
• The inverted repeat sequence is also present and helps in the formation of the hairpin loop (as shown in the image).
• Hence, the statement is correct.

Option 3: Rho-dependent terminators may possess inverted repeat elements.

• In some cases, Rho-dependent terminators could possess inverted repeat elements, but Rho proteins do not rely on these inverted repeat elements for their action.
• Hence the statement is correct.

Option 4: Nus A is necessary for intrinsic transcription termination.

• NusA is not a necessary element for intrinsic transcription termination.
• It might enhance transcription termination in some cases but only as an accessory element.
• Hence, this option is incorrect.

Additional Information

Other mode of termination -

• It is reported in bacteria and is Mfd dependent.
• Mfd-dependent termination occurs with the help of Mfd protein which is a type of DNA translocase and requires ATP for its action just like Rho.

Hence, the correct answer is option 4.

The correct answer is Option 3 i.e.Cdc45

Concept:

• DNA replication in eukaryotes could be divided into three major parts:
  • Initiation
  • Elongation
  • Termination.
• DNA replication initiation could be divided into:
  •  pre-replicative complex
  •  initiation complex.
• Pre-replicative complex majorly consists of
  • ORC (origin recognition complex)+ Cdc6 + Cdt + MCM complex (mini-chromosome maintenance complex)
• Initiation complex consists of 
  • Cdc45 + MCM 10 + GINS + DDK and CDK kinase + Dpb11, Sld3, Sld2 protein complex.

Explanation:

• All the proteins given in the options belong to eukaryotic cells and so we must consider only eukaryotic DNA replication here.

Option 1: ORC - INCORRECT

• DNA replication is initiated from the origin of replication, having specific sequences to initiate replication.
• The ORC is a hexameric DNA binding complex that binds with the origin of replication followed by the recruitment of Cdc6 protein followed by Cdt1.
• ORC dephosphorylates and becomes inactivated before the elongation process.
• Hence, this option is incorrect. 

Option 2: Geminin - INCORRECT

• It binds to cdt1 to prevent the re-initiation of DNA replication and hence it works as a regulator/inhibitor rather than an initiator of DNA replication.
• It is an inhibitor of Cdt1.

Option 3: Cdc45 - CORRECT

• Cdc refers to the cell division control proteins that are involved in various steps of DNA replication process.
• Cdc45 remains with MCM complex and GINS to work as a helicase.
• Thus, it helps in the initiation of DNA replication as well as advancement of the replication fork.

​Option 4: Cdc6 - INCORRECT

• It helps in the assembling of the pre-replicative complexes and interacts with the ORC.
• Cdc6 degrades before initiation of the replication fork.
• The concentration of both cdc6 and cdt1 declines before DNA elongation starts.

​Hence, the correct option is option 3.

Concept:

• Chromatin condensation is a process by which chromatin gets densely packaged and reduced in volume for the broader purpose of gene regulation.
• Subsets of chromatins are:
  1. Heterochromatin - transcriptionally inactive part due to dense chromatin condensation.
  2. Euchromatin - transcriptionally active part due to comparatively loose chromatin condensation or presence of expanded DNA regions for transcription.

Explanation:

HP1 - 

• HP1 is a family of non-histone chromosomal proteins found in mammals.
• HP1 has three paralogs: HP1alpha, HP1 beta and HP1 gamma.
• HP1 belongs to the heterochromatin protein 1 family, which binds to methylated histone H3 at the lysine 9 position and represses DNA transcription of the region.

SIR Complex- 

• SIR (silent information regulator) proteins are nuclear proteins found in budding yeast (Saccharomyces cerevisiae).
• These proteins form specialized chromatin structures that resemble heterochromatin of higher eukaryotes.
• SIR-3 is known to be the primary structural component of SIR proteins of heterochromatin condensation.
• SIR 2-4 complex helps in the recruitment of other SIR proteins.

Su(var) - 

• The role of Su(var) heterochromatin protein is seen in Drosophila only.
• It controls position effect variegation in Drosophila by methylation at H3-K9 position.

Hence, the correct option is option 2.

The correct answer is  Pseudopodia.

Key Points

• The change in shape in amoeba which facilitates movement is due to Pseudopodia.
• The pseudopodia extends from the two sides of the food molecule and surrounds it and finally engulfs the food.
• Pseudopodia is used in movement and as a tool to capture prey or obtain required nutrition.

Structure of Amoeba:

Additional Information 

The correct answer is Option 4 i.e.Brugiya malayi

Concept:

• Filariasis is a parasitic disease caused by the spread of roundworms belonging to the Filarioidea type.
• These parasites are spread via mosquitoes or other blood-feeding insects.
• This disease is found in subtropical regions (hot, humid, and damp regions) such as South Asia, South Africa, the South Pacific, and parts of South America.
• Humans are their definitive hosts.

• Depending on the major affected areas of the human body, this disease is categorized into:
  • Lymphatic filariasis
  • Subcutaneous filariasis
  • Serous cavity filariasis

Explanation:

Option 1: Listeria monocytogenes

• It is a pathogenic bacteria that causes listeriosis.
• It is usually transmitted by contaminated food.
• It causes serious infection and severely affects pregnant women and older people.
• Hence, this option is incorrect.

Option 2: Cryptococcus neoformans

• This is an encapsulated yeast-like fungus that causes cryptococcal meningitis.
• It is life-threatening only in immunocompromised patients like AIDS patients.
• Hence, this option is incorrect.

Option 3: Francisella tularensis

• It is a gram-negative bacteria that causes tularemia.
• It is a zoonotic pathogen that causes febrile conditions in affected person.
• In this disease, the affected person suffers from respiratory troubles like cough and breathing problems.
• Hence, this option is incorrect.

Option 4: Brugiya malayi

• It is one of the filarial nematodes that causes lymphatic filariasis in humans.
• The Mansonia and Aedes mosquitoes are the known vectors for this nematode species.
• They are exclusively found in south-east Asia.
• Hence, this option is correct.

Hence, the correct answer is Brugiya malayi.

The correct answer is Option 4 i.e.Opines are a source of nitrogen for Agrobacterium cells.

Concept:

• Agrobacterium tumefaciens and A. rhizogenes are two species of Agrobacterium that are gram-negative soil bacteria.
• Ti plasmid is a plasmid that is present in the A. tumefaciens.
• Agrobacterium are also called natural genetic engineers because of their ability to naturally transformed plants.
• A. tumefaciens causes crown gall disease in some plants.

Ti plasmid - 

• It is a large-sized tumour-inducing plasmid. 
• A. tumifaciens infect wounded or damaged plant tissue and cause the formation of Crown gall disease. 
• Following are three important regions present in Ti-plasmid.

1. T-DNA region - 
   • This region has genes for the synthesis of auxin, cytokinins, and opine. It is flanked by the left and right borders of the T-DNA region.
   • It contains a set of 24-kb sequences that is flanked on either side of the T-DNA region. 
   • Right border is more critical in transfer of Ti plasmid in plant.  
2. Virulence region - 
   • The genes that help in the transfer of the T-DNA in the plant is located outside T-DNA. 
   • At least, 9 different vir genes are identify in the plant. 
3. Opine catabolism region - 
   • This region contains genes that are involved in uptake and metabolism of opine.

Important Points

Option 1: INCORRECT

• The virulence region of the Ti plasmid contains 9 vir genes.
• Out of 9 vir genes, vir A and vir G are the only two vir genes that are constitutively expressed. 

Option 2: INCORRECT

• The integration of T-DNA into the plant genome is based on the specific DNA sequence that is present at the right border of T-DNA.
• If any gene or DNA sequence is present in this T-DNA region then it is also transferred and gets integrated into the nuclear genome of the plant. 
• The integration of the T-DNA region in the nuclear genome of a plant occurs at an approximate random location through non-homologous recombination. 

Option 3: INCORRECT

• Host plants encode proteins that play any role in the Agrobacterium-mediated transfer of T-DNA into plant cells and integration of T-DNA region in the plant genome.

Option 4: CORRECT

• Ti plasmid contains the different types of opine genes i.e., nopaline, octopine, and atropine. 
• These opines are condensation products of either amino acids or keto acids or amino acids and sugar. 
• These opines are used as a source of nitrogen and carbon for Agrobacterium.

Hence, the correct answer is Option 4.

The correct answer is Option 4 i.e. Asialoglycoprotein

Concept:

Cytoplasmic domains of any receptor bind with different proteins and signals cell for specific functions accordingly.

A cell has two types of receptors:

1. Cytoplasmic receptors -
   • These are found in the cytoplasm of a cell and respond to hydrophobic ligands.
   • They are also known as internal or intracellular receptors.
2. Transmembrane receptors -
   • These are membrane-anchored receptors that are also known as integral membrane proteins.
   • Transmembrane receptors bind to extracellular signals and transmit them into the intracellular environment.

Tyrosine kinase receptors (RTK) - 

• They belong to the high-affinity cell surface receptor category and aid in the binding of many growth factors, cytokines and hormones.
• RTKs possess intrinsic cytoplasmic enzymatic activity which catalyzes the transfer of phosphate from ATP to a tyrosine residue in protein substrates.
• Epidermal growth factor, platelet-derived growth factor, and insulin function as a protein that binds to tyrosine kinase receptors.

Explanation:

Option 1: Epidermal growth factor (EGF)

• EGF receptor (EGFR) is a transmembrane protein that binds to EGF.
• EGFR contains a cytoplasmic tyrosine kinase active site.
• It is expressed in the human body at multiple locations like gums, placenta, vulva, superficial temporal artery, human penis, urethra, mouth cavity, etc.
• Hence, this option is incorrect.

Option 2: Platelet-derived growth factor (PDGF)

• The receptors of PDGF belongs to family of cell surface tyrosine kinase receptors.
• These function for cell proliferation, cellular growth and differentiation.
• Hence, this option is incorrect.

Option 3: Insulin

• The insulin receptors are heterotetrameric transmembrane glycoproteins.
• It contains 2 α-subunits and 2 β-subunits.
• They have one transmembrane domain and one tyrosine-kinase cytoplasmic domain.
• Hence, this option is incorrect.

Option 4: Asialoglycoprotein

• Asialogycoprotein and glycoprotein binds to asialoglycoprotein receptors (ASGPR).
• ASGPR are transmembrane receptors which are specifically present on hepatocytes (liver cells) and thus also called as hepatic lectin.
• The human ASGPR has 4 functional domains:
  • Cytoplasmic domain
  • Transmembrane domain
  • Stalk
  • Carbohydrate recognition domain (CRD)
• The cytoplasmic or cytosolic domain does not act as a tyrosine kinase here.
• Hence, this option is correct. 

Thus, the correct answer is Asialoglycoprotein.

The correct answer is Protoderm.

Key Points

• Protoderm is the outermost primary meristem in plants.
• In roots, it differentiates to form the epidermis.
• Produces epidermal cells, including root hairs.
• Root hairs play a crucial role in water and nutrient absorption.
• Acts as a protective barrier.
• Facilitates root-soil interactions.

Additional Information

• Axillary buds, located at leaf-stem junctions, can grow into branches or flowers, influenced by hormonal signals and environmental factors. 
• A leaf primordium is the initial embryonic tissue from which a leaf develops, found at the shoot apex or growing tip.
• Vascular tissue in plants consists of xylem and phloem.
• Xylem transports water and minerals from roots, providing structural support with tracheids, vessels, and fibers. 
• Phloem transports sugars and nutrients throughout the plant.   

The correct answer is Cdk2/Cyclin E

Concept:

• Cell cycle is a highly regulated and ordered series of events. The engines that derive the progression from one step of the cell cycle to the next are cyclin-CDK complexes.
• These complexes are composed of two subunits- cyclin and cyclin-dependent protein kinase. Cyclin is a regulatory protein whereas CDK is a catalytic protein and acts as serine/threonine protein kinase.
• Cyclins are so named as they undergo a cycle of synthesis and degradation in each cycle.   
• Humans contain four cyclins- G1 cyclins, G1/S cyclins, S cyclins, and M cyclins.

Explanation:

• Cyclin-CDK complexes trigger the transition from G1 to the S phase and from G2 to the M phase by phosphorylating a distinct set of substrates.
• According to the classical model of cell cycle control, D cyclins and CDK4/CDK6 regulate events in the early G1 phase. Cyclin E-CDK2 regulates the completion of the S-phase.
• The transition from G2 to M is driven by sequential activity of cyclin A-CDK1 and cyclin B-CDK1 complexes.

So, the correct answer is Option 2.