Unified Exam — Biology (Armenia)

Which cell organelle is surrounded by a double membrane and possesses its own circular DNA and 70S ribosomes, supporting the endosymbiotic theory?

• AMitochondria (and Chloroplasts)
• BEndoplasmic reticulum
• CGolgi apparatus
• DLysosomes

In which phase of the eukaryotic cell cycle does DNA replication (synthesis) take place?

• AS phase of Interphase (Synthesis phase)
• BG1 phase of Interphase
• CG2 phase of Interphase
• DM phase (Mitosis / Prophase)

If a segment of a template DNA strand has the sequence 3'-TAC GGA CTT GAT-5', what is the complementary mRNA sequence synthesized during transcription?

• A5'-AUG CCU GAA CUA-3'
• B5'-UAC GGA CUU GAU-3'
• C5'-ATG CCT GAA CTA-3'
• D3'-AUG CCU GAA CUA-5'

How many molecules of ATP are generated per molecule of glucose during aerobic cellular respiration in eukaryotic cells (glycolysis, pyruvate oxidation, Krebs cycle, and oxidative phosphorylation)?

• A36 to 38 ATP molecules (or ~30–32 ATP in modern biochemical models)
• B2 ATP molecules
• C4 ATP molecules
• D100 ATP molecules

During which phase of meiosis do homologous chromosome pairs undergo synapsis and crossing over (recombination)?

• AProphase I
• BMetaphase I
• CAnaphase I
• DProphase II

What is the primary function of lysosomes in animal cells?

• AIntracellular digestion and autophagy of cellular waste via acid hydrolases
• BSynthesis of ribosomal RNA and ribosomal subunits
• CLipid and steroid hormone biosynthesis
• DGeneration of cellular ATP via oxidative phosphorylation

What is the phenotypic ratio in the F2 generation of a classic Mendelian monohybrid cross between two heterozygous individuals (Aa x Aa) with complete dominance?

• A3 : 1 (Dominant to Recessive phenotype)
• B1 : 2 : 1 (Genotypic ratio: 1 AA : 2 Aa : 1 aa)
• C9 : 3 : 3 : 1 (Dihybrid F2 ratio)
• D1 : 1

A woman with normal vision whose father was color-blind (carrier: X^D X^d) marries a man with normal vision (X^D Y). What is the probability that their first son will be red-green color-blind?

• A50% (1/2 of sons will inherit the X^d allele)
• B25% (of all children, but 50% of sons)
• C100%
• D0%

In a population in Hardy-Weinberg equilibrium, the frequency of homozygous recessive individuals (aa) is q² = 0.04 (4%). What is the frequency of heterozygous carriers (2pq) in this population?

• A0.32 (32%)
• B0.20 (20%)
• C0.64 (64%)
• D0.16 (16%)

Which of the following structures represents homologous organs sharing a common evolutionary origin despite performing different functions?

• AThe human arm, bat wing, whale flipper, and horse foreleg (divergent evolution)
• BThe bird wing and insect wing (analogous organs / convergent evolution)
• CThe eye of an octopus and human eye
• DThe shark fin and dolphin flipper

Which chamber of the human heart has the thickest muscular wall (myocardium) because it must pump oxygenated blood into the high-pressure systemic aorta?

• ALeft ventricle (Ձախ փորոք)
• BRight ventricle (Աջ փորոք)
• CLeft atrium (Ձախ նախասիրտ)
• DRight atrium (Աջ նախասիրտ)

What is the structural and functional filtration unit of the human kidney?

• ANephron (composed of glomerulus, Bowman's capsule, and renal tubules)
• BNeuron
• CAlveolus
• DOsteon

Which hormone secreted by the beta cells of the Islets of Langerhans in the pancreas lowers blood glucose concentration by stimulating cellular uptake and glycogenesis?

• AInsulin (Ինսուլին)
• BGlucagon (produced by alpha cells)
• CAdrenaline (Epinephrine)
• DCortisol

What is the primary site of nutrient digestion and absorption in the human digestive tract, equipped with circular folds, villi, and microvilli?

• ASmall intestine (specifically the duodenum, jejunum, and ileum)
• BStomach
• CLarge intestine (Colon)
• DEsophagus

Which part of the human brain coordinates voluntary motor movement, fine balance, posture, and muscle tone?

• ACerebellum (Ուղեղիկ)
• BMedulla oblongata (Երկարավուն ուղեղ)
• CHypothalamus (Ենթատեսաթումբ)
• DCorpus callosum

Which blood group in the ABO system is considered the universal red blood cell donor because its erythrocytes lack both A and B surface agglutinogens (antigens)?

• AGroup O (I) Rh-negative
• BGroup AB (IV) Rh-positive (Universal recipient)
• CGroup A (II)
• DGroup B (III)

Which plant tissue (vascular element) is composed of living sieve tube elements and companion cells responsible for transporting organic nutrients (sucrose) from photosynthetic leaves to sink organs?

• APhloem (Մաղանոթներ / Լուբ)
• BXylem (Tracheids and vessels - transports water and minerals)
• CSclerenchyma
• DCollenchyma

What is the unique reproductive process in flowering plants (angiosperms) where one sperm nucleus fertilizes the egg cell (forming a 2n zygote) and a second sperm nucleus fuses with the central binucleate cell (forming 3n triploid endosperm)?

• ADouble fertilization (Կրկնակի բեղմնավորում - discovered by S. Nawaschin)
• BParthenogenesis
• CVegetative propagation
• DSelf-pollination

Which phylum of invertebrate animals is characterized by bilateral symmetry, a segmented body (metamerism), a closed circulatory system with hemoglobin-like pigment, and nephridial excretory organs?

• AAnnelida (Segmented worms / e.g., Earthworm, Leech)
• BNematoda (Roundworms / pseudocoelomate)
• CPlatyhelminthes (Flatworms / acoelomate)
• DArthropoda

What is the 10% ecological rule (Lindeman's rule of trophic efficiency) regarding energy transfer across trophic levels in an ecosystem?

• AOnly approximately 10% of the energy stored as biomass in one trophic level is incorporat…
• B10% of solar radiation is captured by plants during photosynthesis
• C90% of energy is stored at the top carnivore level
• DEcosystem biomass increases by 10% every year

What is the start codon in the standard mRNA genetic code, and which amino acid does it specify in eukaryotes?

• AAUG, encoding Methionine (Met)
• BUAA, encoding Stop
• CUGA, encoding Tryptophan
• DGUG, encoding Valine

Which enzyme unzips and unwinds the DNA double helix at the replication fork during DNA replication by breaking hydrogen bonds between complementary bases?

• ADNA Helicase
• BDNA Polymerase III
• CDNA Ligase
• DRNA Primase

What is the primary biological function of the light-dependent reactions of photosynthesis occurring on thylakoid membranes?

• APhotolysis of water, evolving O2 gas, and generating ATP and NADPH to power the Calvin cy…
• BFixation of CO2 into glucose via RuBisCO
• COxidation of glucose to pyruvate
• DSynthesis of cellulose cell walls

Which of the following genetic diseases in humans is caused by chromosomal non-disjunction resulting in trisomy of chromosome 21 (47, XX,+21 or 47, XY,+21)?

• ADown syndrome (Դաունի համախտանիշ)
• BTurner syndrome (45, X0)
• CKlinefelter syndrome (47, XXY)
• DHuntington's chorea

What is the primary mechanism of evolutionary change proposed by Charles Darwin in 1859?

• ANatural selection acting upon heritable phenotypic variation within a population
• BInheritance of acquired characteristics (Lamarckism)
• CSpontaneous macromutational speciation (Saltation)
• DGeomagnetic field shifts

In a dihybrid cross between two heterozygous pea plants with yellow round seeds (YyRr x YyRr), what proportion of the F2 offspring is expected to have green wrinkled seeds (yyrr)?

• A1/16 (approx 6.25%)
• B9/16
• C3/16
• D1/4

Which of the following blood vessels carries deoxygenated blood from the right ventricle of the heart to the lungs for gas exchange?

• APulmonary artery (Թոքային զարկերակ)
• BPulmonary vein (Թոքային երակ - carries oxygenated blood)
• CAorta (Աորտա)
• DSuperior vena cava (Վերին սիներակ)

What gas exchange process occurs in the pulmonary alveoli between alveolar air and capillary blood?

• APassive diffusion along concentration/partial pressure gradients (O2 into blood, CO2 into…
• BPrimary active transport via ATP pumps
• CPinocytosis
• DFacilitated osmosis

Which component of gastric juice activates the inactive proenzyme pepsinogen into active pepsin and maintains a strongly acidic environment (pH 1.5–2.0)?

• AHydrochloric acid (HCl, secreted by parietal cells)
• BSodium bicarbonate (NaHCO3)
• CBile salts
• DTrypsin

What is the primary target organ of thyroid-stimulating hormone (TSH), secreted by the anterior pituitary gland (adenohypophysis)?

• AThyroid gland (stimulating production of thyroxine T4 and triiodothyronine T3)
• BAdrenal cortex
• CPancreatic islets
• DMammary glands

Which cellular component of blood lacks a nucleus and organelles at maturity in mammals, maximizing space for hemoglobin to transport oxygen?

• AErythrocytes (Red blood cells / Էրիթրոցիտներ)
• BLeukocytes (White blood cells)
• CPlatelets (Thrombocytes)
• DLymphocytes

What type of immunity is established when a person receives a vaccination containing attenuated or inactivated pathogens?

• AArtificially acquired active immunity
• BArtificially acquired passive immunity (receiving ready-made antiserum antibodies)
• CNaturally acquired active immunity (recovering from actual clinical infection)
• DInnate non-specific immunity

Which sensory receptor cells located in the human retina are responsible for photopic color vision and high visual acuity in bright light?

• ACones (Սրվակիկներ)
• BRods (Ցուպիկներ - scotopic black-and-white night vision)
• CBipolar cells
• DGanglion cells

What is the function of the myelin sheath produced by Schwann cells (in the PNS) and oligodendrocytes (in the CNS) around axons?

• AElectrically insulates axons and dramatically accelerates action potential propagation vi…
• BStores glycogen for neuronal metabolism
• CSynthesizes neurotransmitters like acetylcholine
• DGenerates cerebrospinal fluid

What is the primary nitrogenous waste product excreted by the human kidneys in urine, formed in the liver via the ornithine urea cycle from toxic ammonia?

• AUrea (Միզանյութ / (NH2)2CO)
• BUric acid (Միզաթթու - birds and reptiles)
• CAmmonia (NH3 - aquatic fish)
• DCreatinine

Which of the following plants belongs to the division Bryophyta (mosses), characterized by the dominance of the haploid gametophyte in its life cycle and absence of true vascular tissues?

• APolytrichum (Hair cap moss)
• BDryopteris (Shield fern)
• CPinus (Pine tree - Gymnosperm)
• DEquisetum (Horsetail)

Which class of vertebrates is characterized by homeothermy (warm-bloodedness), a four-chambered heart with a left aortic arch, mammary glands, hair/fur, and three middle ear ossicles (malleus, incus, stapes)?

• AMammalia (Mammals / Կաթնասուններ)
• BAves (Birds - right aortic arch)
• CReptilia (Reptiles)
• DAmphibia (Amphibians)

What is the symbiotic ecological relationship called where one species benefits while the other species is neither harmed nor helped (e.g., epiphytic orchids growing on tree branches)?

• ACommensalism (Կոմենսալիզմ)
• BMutualism (both benefit)
• CParasitism (one benefits at the expense of the host)
• DAmensalism (one is inhibited while the other is unaffected)

What is the name of the biogeochemical process in which specialized soil bacteria (such as Rhizobium, Azotobacter, and cyanobacteria) convert inert atmospheric dinitrogen gas (N2) into biological ammonia (NH3/NH4⁺)?

• ANitrogen fixation (Ազոտֆիքսացիա)
• BNitrification (conversion of ammonia to nitrite and nitrate)
• CDenitrification (reduction of nitrate back to N2 gas)
• DAmmonification (decomposition of organic nitrogen)

Which of the following organic compounds is a structural polysaccharide that forms the rigid cell wall in plants and consists of beta-1,4-glycosidic linked D-glucose chains?

• ACellulose (Թաղանթանյութ / Ցելյուլոզ)
• BStarch (Alpha-1,4 and alpha-1,6 linked storage polymer)
• CGlycogen (Animal starch)
• DChitin (N-acetylglucosamine polymer in fungi and arthropods)

What is the primary role of tRNA (transfer RNA) molecules during the translation stage of protein synthesis?

• ADelivering specific amino acids to the ribosome by matching its anticodon with the comple…
• BForming the catalytic peptide transferase center of the ribosome
• CCarrying genetic code from the nucleus to the cytoplasm
• DSplicing introns out of pre-mRNA

What is the term for a point mutation in DNA where a single nucleotide substitution replaces one amino acid codon with a premature STOP codon (UAA, UAG, or UGA)?

• ANonsense mutation (Անիմաստ մուտացիա)
• BMissense mutation (replacing one amino acid with another)
• CSilent mutation (synonymous codon coding for the same amino acid)
• DFrameshift mutation

What evolutionary speciation mechanism occurs when a single biological population is geographically partitioned by a physical barrier (mountain range, canyon, river) into isolated gene pools?

• AAllopatric speciation (Ալոպատրիկ / Աշխարհագրական տեսակառաջացում)
• BSympatric speciation (within the same geographic area)
• CPolyploidy speciation
• DArtificial selection

Which of the following blood vessels carries nutrient-rich venous blood directly from the digestive organs (stomach, intestines, pancreas, spleen) to the liver for metabolic processing and detoxification?

• AHepatic portal vein (Դռներակ / Լյարդի դռներակային համակարգ)
• BHepatic vein (Լյարդային երակ - carries blood from liver to inferior vena cava)
• CHepatic artery (Լյարդային զարկերակ)
• DRenal vein

What is the primary role of bile (secreted by the liver and stored in the gallbladder) during lipid digestion in the small intestine?

• AEmulsifying dietary fat globules into microscopic micelles to increase surface area for p…
• BChemically hydrolyzing peptide bonds in proteins
• CBreaking starch down into maltose
• DNeutralizing pancreatic enzymes

Which hormone produced by the posterior pituitary (neurohypophysis) increases water reabsorption in the collecting ducts of the nephron, concentrating the urine and reducing water loss?

• AAntidiuretic hormone (ADH / Vasopressin / Վազոպրեսին)
• BOxytocin
• CAldosterone
• DAtrial natriuretic peptide (ANP)

What is the primary excitatory neurotransmitter responsible for transmitting impulses across the neuromuscular junction to stimulate skeletal muscle contraction?

• AAcetylcholine (ACh / Ացետիլխոլին)
• BGABA (Gamma-aminobutyric acid - inhibitory neurotransmitter)
• CDopamine
• DSerotonin

In the human respiratory cycle, what muscular movements bring about normal quiet inspiration (inhalation)?

• AContraction and flattening of the diaphragm and contraction of external intercostal muscl…
• BRelaxation of the diaphragm and internal intercostals
• CContraction of abdominal wall muscles
• DPassive recoil of lung elastic fibers