Biology MCQs

Question #341

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Which of the following is a correct statement about the human skeleton?

A. The vertebral column is composed of 33 bones in adults.

B. The femur is the smallest bone in the body.

C. The skull consists of 22 bones, all fused into a single unit.

D. The rib cage has 10 pairs of ribs.

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Correct Answer: Option A

Explanation:
The adult vertebral column consists of 33 vertebrae (though some are fused: 5 sacral and 4 coccygeal). The femur (thigh bone) is the longest and strongest bone. The skull is composed of 22 bones (cranium and facial bones), some fused but the mandible is movable. The rib cage has 12 pairs of ribs. The stapes in the ear is the smallest bone.

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Question #342

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The bond that joins amino acids together in a protein is called a:

A. Peptide bond

B. Hydrogen bond

C. Glycosidic bond

D. Phosphodiester bond

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Correct Answer: Option A

Explanation:
A peptide bond is a covalent bond formed between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of another, releasing a water molecule (condensation reaction). Glycosidic bonds link monosaccharides, phosphodiester bonds link nucleotides in DNA/RNA, hydrogen bonds stabilize secondary structures. Peptide bonds create the polypeptide backbone.

This question belongs to: Science Biology

Question #343

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The process by which traits are transferred from parents to offspring is:

A. Heredity

B. Variation

C. Mutation

D. Evolution

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Correct Answer: Option A

Explanation:
Heredity (inheritance) is the transmission of genetic information and traits from parents to offspring through genes. Variation refers to differences among individuals, evolution is the change in heritable traits over generations, and mutation is a change in DNA sequence. Mendel's laws describe the patterns of heredity. Genes are the units of heredity.

This question belongs to: Science Biology

Question #344

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Which of the following is a defining feature of all chordates at some stage of their life?

A. Gills

B. Vertebral column

C. Scales

D. Notochord

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Correct Answer: Option D

Explanation:
All chordates possess a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some stage of development. The notochord may be replaced by the vertebral column in vertebrates. Gills and scales are not universal (e.g., mammals lack both). The notochord provides skeletal support and is the defining feature of the phylum Chordata.

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Question #345

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The accumulation of which chemical compound in the muscles leads to fatigue during strenuous exercise?

A. Acetic acid

B. Lactic acid

C. Glucose

D. Ethanol

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Correct Answer: Option B

Explanation:
During intense exercise, when oxygen supply is insufficient, muscle cells switch to anaerobic glycolysis, producing ATP and lactic acid from glucose. Lactic acid accumulation lowers pH, causing muscle fatigue, soreness, and cramps. It is later converted back to glucose in the liver (Cori cycle). Ethanol is produced by yeast fermentation.

This question belongs to: Science Biology

Question #346

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Which of the following blood cells is responsible for the immune response by producing antibodies?

A. Lymphocytes (B cells)

B. Monocytes

C. Erythrocytes

D. Platelets

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Correct Answer: Option A

Explanation:
B lymphocytes (B cells) differentiate into plasma cells that produce and secrete antibodies (immunoglobulins) specific to antigens, providing humoral immunity. T cells are involved in cell-mediated immunity. Erythrocytes carry oxygen, platelets clot blood, monocytes differentiate into macrophages that phagocytose pathogens. Lymphocytes are a type of white blood cell.

This question belongs to: Science Biology

Question #347

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The term 'test cross' in genetics refers to a cross between an individual with:

A. Two heterozygous individuals

B. Dominant phenotype and homozygous dominant

C. Recessive phenotype and heterozygous

D. Dominant phenotype and homozygous recessive

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Correct Answer: Option D

Explanation:
A test cross is used to determine the genotype of an individual expressing a dominant phenotype by crossing it with a homozygous recessive individual. The resulting phenotypic ratios reveal whether the dominant individual is homozygous (all offspring dominant) or heterozygous (1:1 ratio). It is a valuable tool in genetic analysis.

This question belongs to: Science Biology

Question #348

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The technique used to visualize and separate DNA fragments based on size is:

A. PCR

B. Centrifugation

C. Microscopy

D. Gel electrophoresis

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Correct Answer: Option D

Explanation:
Agarose gel electrophoresis separates DNA fragments by size as they move through the gel under an electric field; smaller fragments migrate faster. DNA is stained with ethidium bromide and visualized under UV light. PCR amplifies DNA, centrifugation separates by density, microscopy provides magnified images. Gel electrophoresis is essential in molecular biology and forensics.

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Question #349

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Which of the following is a correct match between the hormone and its function?

A. Adrenaline - Decreases heart rate

B. Insulin - Increases blood glucose

C. Thyroxine - Controls blood calcium level

D. Oxytocin - Stimulates uterine contractions

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Correct Answer: Option D

Explanation:
Oxytocin stimulates uterine smooth muscle contractions during childbirth and milk ejection during lactation. Thyroxine regulates metabolism; calcitonin and parathyroid hormone control blood calcium. Insulin lowers blood glucose. Adrenaline increases heart rate, not decreases. This question tests the core functions of major hormones.

This question belongs to: Science Biology

Question #350

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The disease 'pellagra' is caused by the deficiency of:

A. Vitamin B₃ (Niacin)

B. Vitamin B₂ (Riboflavin)

C. Vitamin B₁ (Thiamine)

D. Vitamin B₆ (Pyridoxine)

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Correct Answer: Option A

Explanation:
Pellagra, characterized by dermatitis, diarrhea, and dementia (3 Ds), is caused by a deficiency of niacin (vitamin B₃) or its precursor tryptophan. It is common in populations with corn-based diets lacking tryptophan. Beriberi is due to B₁ deficiency, cheilosis to B₂, peripheral neuropathy to B₆. Niacin is a component of coenzymes NAD and NADP.

This question belongs to: Science Biology

Question #351

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In C3 plants, the primary CO₂ acceptor is:

A. Ribulose-1,5-bisphosphate (RuBP)

B. Phosphoenolpyruvate (PEP)

C. Malate

D. Oxaloacetic acid (OAA)

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Correct Answer: Option A

Explanation:
In C3 plants (e.g., wheat, rice), CO₂ is fixed by the enzyme RuBisCO, which catalyzes the reaction between CO₂ and RuBP, producing two molecules of 3-phosphoglycerate (3-PGA), a three-carbon compound. In C4 plants, the primary acceptor is PEP, leading to four-carbon OAA. C3 plants are the most common, but are less efficient in hot, dry conditions due to photorespiration.

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Question #352

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The release of ovum from the ovary is called:

A. Menstruation

B. Implantation

C. Ovulation

D. Fertilization

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Correct Answer: Option C

Explanation:
Ovulation is the process where a mature ovum (secondary oocyte) is released from the Graafian follicle of the ovary, typically around day 14 of the menstrual cycle, triggered by the LH surge. The ovum is captured by the fimbriae of the fallopian tube. Fertilization is fusion with sperm, menstruation is shedding of the uterine lining, implantation is embedding of the blastocyst.

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Question #353

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Which of the following microorganisms is used for the production of citric acid in the industry?

A. Rhizobium leguminosarum

B. Aspergillus niger

C. Saccharomyces cerevisiae

D. Penicillium chrysogenum

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Correct Answer: Option B

Explanation:
Aspergillus niger is a fungus widely used for the industrial production of citric acid (a common food additive) through fermentation. Penicillium chrysogenum produces penicillin, Saccharomyces cerevisiae is used in baking and brewing, Rhizobium is a nitrogen-fixing bacterium. Citric acid is used as a preservative and flavor enhancer.

This question belongs to: Science Biology

Question #354

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The process by which plants synthesize food using light energy is:

A. Photosynthesis

B. Transpiration

C. Chemosynthesis

D. Respiration

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Correct Answer: Option A

Explanation:
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy (glucose) using carbon dioxide and water, releasing oxygen. It occurs in chloroplasts. Respiration releases energy from organic molecules. Transpiration is water loss. Chemosynthesis uses chemical energy (by some bacteria).

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Question #355

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The region of the root where root hairs are formed is the:

A. Meristematic zone

B. Zone of maturation

C. Zone of elongation

D. Root cap

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Correct Answer: Option B

Explanation:
Root hairs are unicellular extensions of epidermal cells found in the zone of maturation (differentiation) of the root, just behind the zone of elongation. They increase surface area for water and mineral absorption. The root cap protects the tip, the meristematic zone contains dividing cells, and the elongation zone causes root lengthening.

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Question #356

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The nitrogenous waste that requires the least amount of water for excretion is:

A. Urea

B. Guanine

C. Ammonia

D. Uric acid

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Correct Answer: Option D

Explanation:
Uric acid is the least toxic and most water-insoluble nitrogenous waste, excreted as a paste or solid pellet, requiring minimal water. It is produced by birds, reptiles, and insects (uricotelic organisms). Ammonia (ammonotelic) is highly toxic, requiring large water volumes (e.g., fish). Urea (ureotelic) is intermediate, excreted by mammals.

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Question #357

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The type of inheritance in which the phenotype of the offspring is intermediate between the two parents is called:

A. Polygenic inheritance

B. Complete dominance

C. Incomplete dominance

D. Codominance

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Correct Answer: Option C

Explanation:
Incomplete dominance occurs when neither allele is completely dominant, resulting in a heterozygous phenotype that is a blend (e.g., red × white snapdragons produce pink). Codominance shows both alleles fully expressed (e.g., AB blood type). Complete dominance shows one allele masking another. Polygenic inheritance involves multiple genes contributing to a continuous trait.

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Question #358

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The functional region of an antibody that binds to an antigen is called the:

A. Fc region

B. Disulfide bridge

C. Constant region

D. Variable region

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Correct Answer: Option D

Explanation:
The variable (V) region at the tips of the antibody Y-shape contains the antigen-binding site, which is specific to a particular antigen. The constant region determines the class (IgG, IgM, etc.) and effector functions. The Fc region binds to immune cell receptors. Variability in the V region is generated by gene rearrangement, allowing immense antibody diversity.

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Question #359

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In the human eye, the image is formed on the:

A. Lens

B. Optic nerve

C. Cornea

D. Retina

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Correct Answer: Option D

Explanation:
The retina is the light-sensitive inner layer of the eye containing photoreceptors (rods and cones) where an inverted real image is formed. The cornea and lens focus light onto the retina. The optic nerve transmits impulses from the retina to the brain for interpretation. The fovea centralis is the point of sharpest vision.

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Question #360

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The first successfully cloned mammal, Dolly the sheep, was produced using:

A. Artificial insemination

B. Somatic cell nuclear transfer

C. Recombinant DNA technology

D. Gene therapy

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Correct Answer: Option B

Explanation:
Dolly (1996) was created by somatic cell nuclear transfer (SCNT), where the nucleus from an adult somatic cell (udder) was transferred into an enucleated egg cell, which was then implanted in a surrogate. This proved that differentiated somatic cells can be reprogrammed to totipotency. She was the first mammal cloned from an adult cell.

This question belongs to: Science Biology

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