AKU MBBS Admission Test Biology Syllabus

What is the approximate net ATP yield from aerobic versus anaerobic respiration of one glucose molecule?

Aerobic respiration yields about 36-38 ATP; anaerobic respiration yields only 2 ATP.

State Mendel's Law of Segregation.

The two alleles of a gene separate (segregate) during gamete formation so that each gamete carries only one allele of each gene.

State Mendel's Law of Independent Assortment.

Alleles of different genes assort independently of one another during gamete formation (applies to genes on different chromosomes).

In a monohybrid cross between 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.

Define the terms genotype and phenotype.

Genotype is the genetic (allelic) makeup of an organism; phenotype is the observable physical/biochemical characteristics resulting from genotype and environment.

Describe the semi-conservative model of DNA replication.

The two strands of the parent DNA separate, and each acts as a template for a new complementary strand, so each daughter molecule has one old and one new strand.

Name the two main stages of gene expression (protein synthesis) and where each occurs.

Transcription (DNA to mRNA, in the nucleus) and translation (mRNA to polypeptide, at the ribosomes in the cytoplasm).

What is a codon and how many codons specify start and stop signals?

A codon is a sequence of three mRNA bases coding for one amino acid; AUG is the start codon (also methionine) and there are three stop codons (UAA, UAG, UGA).

State the base-pairing rules in DNA and the difference in RNA.

In DNA: adenine pairs with thymine, cytosine pairs with guanine. In RNA, thymine is replaced by uracil (adenine pairs with uracil).

What is the difference between a gene mutation and a chromosomal mutation?

A gene (point) mutation is a change in the base sequence of a single gene (e.g. substitution, insertion, deletion); a chromosomal mutation is a change in chromosome number or structure.

Name the three types of point mutation by their effect on the protein.

Silent (no change in amino acid), missense (different amino acid), and nonsense (premature stop codon). Frameshifts arise from insertions/deletions.

How many pairs of chromosomes do humans have, and how are they classified?

23 pairs (46 total): 22 pairs of autosomes and 1 pair of sex chromosomes (XX in females, XY in males).

What chromosomal abnormality causes Down syndrome?

Trisomy 21 — an extra copy of chromosome 21 (47 chromosomes), usually due to non-disjunction during meiosis.

Distinguish between continuous and discontinuous variation.

Continuous variation shows a range of values with no distinct categories (e.g. height), often polygenic; discontinuous variation shows distinct categories with no intermediates (e.g. blood group).

What is the genetic basis and inheritance pattern of sickle cell anaemia?

It is an autosomal recessive disorder caused by a single base substitution in the haemoglobin gene (glutamic acid replaced by valine), producing abnormal HbS and sickle-shaped red cells.

Why is haemophilia more common in males than females?

It is an X-linked recessive disorder; males have only one X chromosome, so a single recessive allele causes the disease, whereas females need two copies.

List the stages of mitosis in order.

Prophase, metaphase, anaphase, and telophase (PMAT), followed by cytokinesis.

State three key differences between mitosis and meiosis.

Mitosis produces 2 genetically identical diploid cells in one division; meiosis produces 4 genetically varied haploid cells in two divisions and includes crossing over and independent assortment.

What two events in meiosis create genetic variation?

Crossing over (exchange of segments between homologous chromosomes in prophase I) and independent assortment of homologous chromosomes in metaphase I.

Name the male and female gametes and where each is produced.

The male gamete is the sperm, produced in the testes (seminiferous tubules); the female gamete is the ovum (egg), produced in the ovaries.

List, in order, the path of sperm from production to release.

Seminiferous tubules (testis) -> epididymis -> vas deferens -> ejaculatory duct -> urethra -> out of the penis.

Name the four hormones of the menstrual cycle and one role of each.

FSH stimulates follicle development; LH triggers ovulation; oestrogen rebuilds the uterine lining and triggers an LH surge; progesterone maintains the uterine lining.

What is cell differentiation and how is it possible if all cells have the same DNA?

Differentiation is the process by which unspecialised cells become specialised for a function; it occurs through differential gene expression — different genes are switched on/off in different cell types.

List the main regions of the digestive tract in order from mouth to anus.

Mouth -> oesophagus -> stomach -> small intestine (duodenum, jejunum, ileum) -> large intestine (colon) -> rectum -> anus.

Match each digestive enzyme to its substrate: amylase, protease, lipase.

Amylase digests starch (to maltose), protease digests proteins (to amino acids), and lipase digests lipids (to fatty acids and glycerol).

What is the function of villi in the small intestine?

Villi increase the surface area for absorption of digested nutrients; they have a thin wall, rich blood supply, and a lacteal for absorbing fats.

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

Vena cava -> right atrium -> right ventricle -> pulmonary artery -> lungs -> pulmonary vein -> left atrium -> left ventricle -> aorta -> body.

Compare arteries, veins, and capillaries by wall structure and function.

Arteries have thick muscular/elastic walls carrying blood away from the heart at high pressure; veins have thinner walls with valves returning blood to the heart; capillaries are one cell thick for exchange of materials.

What is the role of haemoglobin and where is it found?

Haemoglobin, found in red blood cells, binds oxygen (forming oxyhaemoglobin) in the lungs and releases it to respiring tissues; it also helps transport some carbon dioxide.

Describe gas exchange in the alveoli.

Oxygen diffuses from the alveolar air into the blood capillaries, and carbon dioxide diffuses from the blood into the alveoli, down their concentration gradients across the thin moist alveolar wall.

What are the functional unit of the kidney and the three stages of urine formation?

The nephron; urine forms by ultrafiltration (in the glomerulus/Bowman's capsule), selective reabsorption (in the tubules), and secretion, followed by water reabsorption.

What is osmoregulation and which hormone controls water reabsorption in the kidney?

Osmoregulation is the control of water and solute balance in the body; ADH (antidiuretic hormone) increases water reabsorption in the collecting ducts, producing more concentrated urine.

Name the three main parts of a neuron and the direction of impulse flow.

Dendrites (receive impulses), cell body, and axon (carries impulse away); impulses travel dendrite -> cell body -> axon -> synapse.

What is a reflex arc and list its components in order?

A rapid involuntary response pathway: receptor -> sensory neuron -> relay (interneuron) in spinal cord -> motor neuron -> effector (muscle/gland).

Name the five types of sensory receptors by the stimulus they detect.

Photoreceptors (light), chemoreceptors (chemicals/taste/smell), mechanoreceptors (pressure/touch/sound), thermoreceptors (temperature), and nociceptors (pain).

Contrast the nervous and endocrine systems as control systems.

The nervous system uses electrical impulses, acts rapidly, and has short-lived, localised effects; the endocrine system uses hormones in the blood, acts more slowly, and has longer-lasting, widespread effects.

Which hormones from the pancreas control blood glucose, and what does each do?

Insulin (from beta cells) lowers blood glucose by promoting glucose uptake and glycogen storage; glucagon (from alpha cells) raises blood glucose by stimulating glycogen breakdown.

Define homeostasis and give two examples of variables it regulates.

Homeostasis is the maintenance of a stable internal environment within narrow limits; examples include body temperature, blood glucose, blood pH, and water/osmotic balance.

Explain the principle of negative feedback in homeostasis.

A change in a variable is detected by receptors, triggering a corrective response by effectors that returns the variable toward the set point, thereby reversing the original change.