OAT (Optometry Admission Test) Biology Syllabus

What are the three stages of transcription and the enzyme involved?

Initiation, elongation, and termination, carried out by RNA polymerase, which synthesizes mRNA 5' to 3' from a DNA template.

Describe the roles of mRNA, tRNA, and rRNA in translation.

mRNA carries the codon sequence; tRNA brings amino acids matching codons via its anticodon; rRNA forms the ribosome and catalyzes peptide bond formation.

What is the central dogma of molecular biology?

Genetic information flows DNA -> RNA -> protein, via transcription (DNA to RNA) and translation (RNA to protein). Reverse transcription (RNA to DNA) is an exception.

State Mendel's Law of Segregation and Law of Independent Assortment.

Segregation: the two alleles for a trait separate during gamete formation. Independent Assortment: alleles of different genes assort independently (for unlinked genes).

In a monohybrid cross of two heterozygotes (Aa x Aa), what are the genotypic and phenotypic ratios?

Genotypic ratio 1 AA : 2 Aa : 1 aa; phenotypic ratio 3 dominant : 1 recessive.

What phenotypic ratio results from a dihybrid cross of two double heterozygotes (AaBb x AaBb)?

9:3:3:1 phenotypic ratio for two independently assorting traits.

Differentiate incomplete dominance from codominance.

Incomplete dominance: heterozygote shows a blended intermediate phenotype (e.g., pink). Codominance: both alleles fully and simultaneously expressed (e.g., AB blood type).

How does ABO blood type illustrate multiple alleles and codominance?

Three alleles (IA, IB, i): IA and IB are codominant and both dominant over i. Genotype IAIB gives type AB; ii gives type O.

What is sex-linked (X-linked recessive) inheritance and why are males more often affected?

Genes on the X chromosome; males (XY) are hemizygous, so a single recessive allele is expressed, while females need two copies. Examples: hemophilia, color blindness.

Define genetic linkage and how recombination frequency relates to gene distance.

Linked genes are on the same chromosome and tend to be inherited together. Recombination frequency increases with distance; 1% recombination = 1 map unit (centimorgan).

What is the difference between an operon's inducible and repressible regulation (lac vs trp)?

lac operon is inducible: normally off, turned on by lactose. trp operon is repressible: normally on, turned off when tryptophan (corepressor) is abundant.

Distinguish a point mutation's silent, missense, and nonsense types.

Silent: codon change with same amino acid. Missense: codon change giving a different amino acid. Nonsense: codon changed to a stop codon, truncating the protein.

State the Hardy-Weinberg equations and what they predict.

p + q = 1 and p^2 + 2pq + q^2 = 1, where p^2 = homozygous dominant, 2pq = heterozygous, q^2 = homozygous recessive. They predict allele/genotype frequencies in a non-evolving population.

List the five conditions required for Hardy-Weinberg equilibrium.

No mutation, no gene flow (migration), no genetic drift (large population), random mating, and no natural selection.

Differentiate genetic drift, gene flow, and the bottleneck/founder effects.

Drift: random allele frequency change (strong in small populations). Gene flow: allele movement between populations. Bottleneck: drastic size reduction; founder effect: new population from few individuals.

List the phases of mitosis in order and the key event of each.

Prophase (chromosomes condense), Metaphase (align at metaphase plate), Anaphase (sister chromatids separate), Telophase (nuclei reform); then cytokinesis divides the cytoplasm.

What is the outcome of mitosis in terms of cell number and ploidy?

Mitosis produces 2 genetically identical diploid daughter cells from one parent cell, maintaining the original chromosome number.

How does meiosis differ from mitosis in outcome?

Meiosis has two divisions producing 4 genetically distinct haploid gametes; mitosis has one division producing 2 identical diploid cells.

What are crossing over and the key event of meiosis I?

Crossing over is the exchange of genetic material between homologous chromosomes during prophase I, increasing variation. Meiosis I separates homologous chromosomes (reductional division).

Distinguish meiosis I from meiosis II.

Meiosis I (reductional) separates homologous chromosomes, halving ploidy; meiosis II (equational) separates sister chromatids, like mitosis.

Name the phases of the cell cycle and what occurs in S phase.

G1 (growth), S (DNA synthesis/replication), G2 (growth, prep for division), and M (mitosis). DNA is replicated during S phase.

What are the main cell cycle checkpoints and their roles?

G1/S checkpoint (checks size, nutrients, DNA damage before replication), G2/M checkpoint (checks DNA replication completeness), and the M (spindle) checkpoint (checks chromosome attachment).

What roles do cyclins, CDKs, and p53 play in cell cycle regulation?

Cyclins activate cyclin-dependent kinases (CDKs) to drive cycle progression; p53 is a tumor suppressor that halts the cycle or triggers apoptosis upon DNA damage.

Compare proto-oncogenes and tumor suppressor genes.

Proto-oncogenes promote cell division; mutated, they become oncogenes (gain of function). Tumor suppressors (e.g., p53, Rb) inhibit division; their loss of function promotes cancer.

Distinguish the three main types of cell signaling: autocrine, paracrine, and endocrine.

Autocrine: cell signals itself. Paracrine: signals nearby cells. Endocrine: hormones travel via the bloodstream to distant target cells.

How do steroid hormones differ from peptide hormones in their signaling mechanism?

Steroid (lipid-soluble) hormones cross the membrane and bind intracellular receptors to alter transcription; peptide hormones bind surface receptors and act via second messengers (e.g., cAMP).

What is a G protein-coupled receptor (GPCR) signaling cascade?

A ligand binds the GPCR, activating a G protein that triggers an effector (e.g., adenylyl cyclase), producing second messengers like cAMP that activate protein kinases.

Describe the sequence of an action potential in a neuron.

Resting potential (-70 mV); depolarization as Na+ channels open and Na+ rushes in; repolarization as K+ channels open and K+ exits; hyperpolarization, then return to rest. All-or-none.

What is the role of the myelin sheath and nodes of Ranvier?

Myelin insulates axons, enabling saltatory conduction where the action potential jumps node to node, greatly increasing conduction speed.

How is a chemical synapse transmitted?

An action potential triggers Ca2+ influx at the axon terminal, causing synaptic vesicles to release neurotransmitter, which binds receptors on the postsynaptic membrane.

Trace the path of blood through the heart starting from the vena cava.

Vena cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary valve -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium -> mitral valve -> left ventricle -> aorta.

Compare arteries, veins, and capillaries.

Arteries carry blood away from the heart under high pressure (thick walls); veins return blood (thin walls, valves); capillaries are single-cell-thick sites of gas/nutrient exchange.

How is oxygen transported in blood and what is the Bohr effect?

Oxygen binds hemoglobin in red blood cells. The Bohr effect: increased CO2/H+ (lower pH) decreases hemoglobin's O2 affinity, releasing O2 to active tissues.

What is the functional unit of the kidney and its main processes?

The nephron. It performs filtration (glomerulus), reabsorption, and secretion to form urine, regulating water, electrolytes, and waste (urea).

Outline the role of major digestive enzymes: amylase, pepsin, and lipase.

Amylase digests carbohydrates (starch); pepsin (stomach, acidic) digests proteins; lipase digests fats (lipids) into fatty acids and glycerol.

Compare the actions of insulin and glucagon on blood glucose.

Insulin lowers blood glucose (promotes uptake and glycogen storage); glucagon raises blood glucose (promotes glycogen breakdown and gluconeogenesis). Both from the pancreas.

What hormones do the anterior pituitary and the thyroid produce, and a key function?

Anterior pituitary: TSH, ACTH, FSH, LH, GH, prolactin (controls other glands/growth). Thyroid: T3/T4 (raise metabolic rate) and calcitonin (lowers blood calcium).

Compare the female menstrual cycle hormones FSH, LH, estrogen, and progesterone roles.

FSH stimulates follicle growth; LH surge triggers ovulation; estrogen builds the endometrium; progesterone (from corpus luteum) maintains it for potential pregnancy.

Describe the sliding filament model of muscle contraction.

Actin filaments slide over myosin filaments; myosin heads bind actin, pull (power stroke) using ATP, and Ca2+ regulates by exposing actin binding sites via troponin/tropomyosin.

Differentiate innate (nonspecific) from adaptive (specific) immunity.

Innate immunity is rapid and nonspecific (skin, phagocytes, inflammation); adaptive immunity is slower, specific, and has memory (B cells/antibodies and T cells).

Contrast humoral and cell-mediated immunity.

Humoral immunity: B cells produce antibodies against extracellular pathogens. Cell-mediated immunity: cytotoxic T cells destroy infected/abnormal cells; helper T cells coordinate the response.

List the taxonomic hierarchy from broadest to most specific.

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species (mnemonic: Dear King Philip Came Over For Good Soup).

Name the three domains of life and a defining feature of each.

Bacteria (prokaryotes, peptidoglycan walls), Archaea (prokaryotes, extreme environments, distinct membranes), and Eukarya (membrane-bound nucleus and organelles).

How is a species named under binomial nomenclature?

By Genus + species, both italicized, with the genus capitalized and species lowercase (e.g., Homo sapiens).

Compare Gram-positive and Gram-negative bacteria.

Gram-positive: thick peptidoglycan wall, stains purple. Gram-negative: thin peptidoglycan with an outer lipopolysaccharide membrane, stains pink.

How do bacteria achieve genetic variation without sexual reproduction?

Through transformation (uptake of free DNA), transduction (DNA transfer via bacteriophage), and conjugation (DNA transfer via pilus between cells).

Why are viruses considered acellular and what are the two main replication cycles?

Viruses lack cells/metabolism, needing a host to replicate. Lytic cycle: rapid replication and host lysis. Lysogenic cycle: viral DNA integrates and replicates with the host dormantly.

State Darwin's theory of evolution by natural selection.

Heritable variation exists; individuals with traits better suited to the environment survive and reproduce more (differential reproductive success), so advantageous alleles increase over generations.

Differentiate the main types of natural selection: directional, stabilizing, and disruptive.

Directional: favors one extreme. Stabilizing: favors intermediate, against extremes. Disruptive: favors both extremes against the intermediate.

Compare allopatric and sympatric speciation.

Allopatric speciation occurs with geographic isolation of populations; sympatric speciation occurs without geographic separation (e.g., via polyploidy or niche differentiation).

Contrast convergent and divergent evolution (analogous vs homologous structures).

Convergent evolution: unrelated species evolve similar traits (analogous structures) due to similar environments. Divergent evolution: related species diverge (homologous structures from common ancestry).

Define the ecological terms population, community, and ecosystem.

Population: members of one species in an area. Community: all interacting populations in an area. Ecosystem: the community plus its abiotic (physical/chemical) environment.

Compare the symbiotic relationships mutualism, commensalism, and parasitism.

Mutualism: both benefit (+/+). Commensalism: one benefits, the other unaffected (+/0). Parasitism: one benefits at the other's expense (+/-).

How does energy flow through trophic levels, and what is the 10% rule?

Energy flows from producers to consumers to decomposers; only about 10% of energy transfers to the next trophic level, the rest lost mainly as heat.

Distinguish r-selected from K-selected species.

r-selected: many offspring, little parental care, fast growth, unstable environments. K-selected: few offspring, much care, slower growth, near carrying capacity in stable environments.

What is the difference between primary and secondary ecological succession?

Primary succession begins on bare lifeless substrate with no soil (e.g., after lava); secondary succession occurs where soil remains after a disturbance (e.g., after a fire).

Compare determinate and indeterminate cleavage in early development.

Determinate cleavage: cell fate is fixed early (protostomes). Indeterminate cleavage: each early cell can form a complete organism, allowing identical twins (deuterostomes).

What are the three primary germ layers and the tissues each forms?

Ectoderm (skin, nervous system), mesoderm (muscle, bone, blood, kidneys), and endoderm (gut lining, liver, lungs).

Define induction and differentiation in developmental biology.

Induction: one group of cells influences the developmental fate of neighboring cells via signals. Differentiation: cells become specialized in structure and function through selective gene expression.