In a standard diagram of a nephron, identify the structure corresponding to the region containing the glomerulus and Bowman’s capsule, where podocytes are found lining the capsule inner layer.

• Loop of Henle
• Renal corpuscle (Bowman’s capsule enclosing glomerulus)
• Vasa recta
• Proximal convoluted tubule
• Collecting duct

In a standard diagram of a nephron, identify the tubule segment that descends into the medulla and then ascends back towards the cortex.

• Collecting duct
• Proximal convoluted tubule
• Loop of Henle
• Distal convoluted tubule
• Glomerulus

In a standard diagram of a nephron, identify the final tube segment that passes through the medulla and carries urine towards the renal pelvis.

• Proximal convoluted tubule
• Loop of Henle
• Distal convoluted tubule
• Collecting duct
• Afferent arteriole

In a standard diagram of a nephron, identify the blood vessel that carries blood towards the glomerulus.

• Collecting duct
• Afferent arteriole
• Efferent arteriole
• Peritubular capillaries
• Loop of Henle

Describe and explain how cells of the proximal convoluted tubule (PCT) are adapted for selective reabsorption. Which of the following statements is NOT a correct adaptation or explanation for PCT cells?

• They possess microvilli on their apical surface, creating a large surface area.
• They contain many mitochondria to provide ATP for active transport (e.g., Na+/K+ pump).
• They lack specific transporter proteins, allowing bulk flow of solutes back into the blood.
• Tight junctions between cells prevent paracellular movement, forcing transcellular transport.
• The basal membrane is highly folded, increasing surface area for pumps moving substances towards blood.
• Numerous cotransporter proteins facilitate reabsorption of substances like glucose with sodium ions.

Describe a cross and analysis to determine if a tall pea plant (where tall ‘Le’ is dominant to dwarf ‘le’) is homozygous dominant (LeLe) or heterozygous (Lele). Which statement describes a necessary part of this test cross?

• Cross the tall pea plant with another tall pea plant known to be heterozygous (Lele).
• Cross the tall pea plant with a dwarf pea plant (genotype lele).
• Observe the F1 offspring; if any are tall, the parent was homozygous (LeLe).
• Self-pollinate the tall pea plant and observe the offspring ratio.
• Observe the F1 offspring; if the ratio is 3 tall : 1 dwarf, the parent was heterozygous (Lele).

Gibberellin is a plant growth regulator involved in stem elongation. What is the general term for a molecule, like gibberellin, that binds to specific cellular receptors to trigger a response?

• Enzyme
• Neurotransmitter
• Signalling molecule (or hormone, ligand, plant growth regulator)
• Antibody
• Substrate

Gibberellin affects stem length in pea plants by influencing internode cells. Suggest the cellular response of internode cells to gibberellin and the resulting effect on the plant’s height (the trait Mendel investigated).

• Response: Gibberellin causes cell shrinkage, leading to shorter stems.
• Response: Gibberellin stimulates cell elongation and/or cell division (mitosis) in internodes.
• Effect: Increased internode cell elongation/division leads to taller stems/plants. (Combines Response #2 with Effect)
• Effect: Gibberellin primarily increases root growth, indirectly affecting height.

Cystic fibrosis is an autosomal recessive disease. Explain the meaning of ‘homozygous’ and ‘recessive’. Which statement correctly defines one or both of these terms?

• Homozygous means having two different alleles; Recessive means the allele is expressed when heterozygous.
• Homozygous means having identical alleles for a gene; Recessive means the allele’s effect is masked by a dominant allele if heterozygous.
• Homozygous means identical phenotype; Recessive means stronger allele.
• Homozygous means having one dominant and one recessive allele; Recessive means determines phenotype.

In the UK 2020 population (67,100,000), 10,800 people had cystic fibrosis (autosomal recessive, genotype aa). Use the Hardy-Weinberg principle (p + q = 1; p² + 2pq + q² = 1) to estimate the frequency of the recessive allele (q) and the frequency of heterozygous carriers (2pq).

• q ≈ 0.0127; 2pq ≈ 0.0251
• q² ≈ 0.000161; p ≈ 0.0127
• q ≈ 0.000161; 2pq ≈ 0.9749
• q² ≈ 1.61 x 10⁻⁴; q ≈ 0.9873
• q ≈ 0.0127; p ≈ 0.0251

The Hardy-Weinberg calculation often estimates carrier frequency based on the prevalence of the disease in the current population. Explain how the difference in life expectancy (individuals with CF ≈ 50 years, general population ≈ 80 years) might affect the accuracy of this estimate for CF carriers.

• The calculation accurately reflects the current gene pool frequency regardless of life expectancy.
• Natural selection against the CF phenotype means affected individuals have lower survival/reproduction rates, potentially making the calculated allele frequency (q) based on living individuals slightly lower than the true frequency in the total gene pool (including past generations), thus underestimating carriers (2pq).
• Shorter life expectancy means affected individuals reproduce more quickly, increasing the allele frequency.
• The Hardy-Weinberg principle only applies if life expectancy is equal for all genotypes.
• Longer life expectancy of carriers increases the accuracy of the calculation.

Data shows the median predicted life expectancy for people born with CF in the UK increased from 38.8 years (born 2008) to 50.6 years (born 2020). National newborn screening for CF was introduced in 2007. Which statement best describes this trend and the likely contribution of screening?

• Life expectancy decreased, likely due to side effects of screening.
• Life expectancy increased significantly, partly because early screening allows for earlier diagnosis and initiation of treatments (like physiotherapy, nutritional support, antibiotics), improving long-term outcomes.
• Life expectancy remained constant, indicating screening had no effect.
• Life expectancy increased, primarily due to general improvements in healthcare unrelated to CF-specific screening or treatment.
• Life expectancy increased, because screening itself cures the disease.

Discuss the ethical and social considerations of offering genetic testing for CF carrier status (heterozygosity) to adults with a family history of the condition. Which point represents a potential disadvantage or negative consideration?

• Allows individuals to make informed reproductive choices (e.g., regarding partner screening, use of prenatal diagnosis or preimplantation genetic diagnosis).
• May cause psychological distress, anxiety, or feelings of guilt if an individual is found to be a carrier, especially concerning potential risks to offspring.
• Can reduce anxiety and provide relief for individuals if the test result is negative (confirming they are not a carrier).
• Allows for better financial planning regarding potential future healthcare costs associated with having an affected child, although this is complex.
• Enables other potentially at-risk family members (e.g., siblings) to better understand their own carrier risk and consider testing.

Data shows that from April to August, mean daily air temperature generally increases (e.g., from ~10°C to ~18°C), while mean monthly milk yield per cow in Holstein Friesians generally decreases (e.g., from ~795 kg to ~714 kg). What type of correlation does this suggest between air temperature and milk yield in this period?

• Positive correlation (higher temperature leads to higher yield)
• No correlation
• Negative correlation (higher temperature leads to lower yield)
• Curvilinear correlation
• Perfect correlation

Milk yield in cattle shows a range of values with intermediate phenotypes, is affected by environmental factors like temperature, and is influenced by multiple genes. What type of phenotypic variation is milk yield, and what are the main contributing factors?

• Type: Discontinuous variation; Factors: Genetics only.
• Type: Continuous variation; Factors: Environment only.
• Type: Discontinuous variation; Factors: Environment only.
• Type: Continuous variation; Factors: Genetics (polygenic) and Environment.
• Type: Continuous variation; Factors: Genetics (single gene) only.

In Holstein Friesian cattle, a specific ‘SLICK’ allele helps with heat tolerance. Comparing cattle with and without this allele: In March (5°C), milk yield was similar (~782 kg with SLICK vs ~798 kg without). In September (14°C), yield was significantly higher in SLICK cattle (~775 kg) compared to normal cattle (~695 kg), whose yield dropped considerably from March. What does this suggest about the effect of the SLICK allele?

• The SLICK allele significantly reduces milk yield at all temperatures.
• The SLICK allele has no effect on milk yield.
• The SLICK allele primarily increases milk yield at lower temperatures.
• The SLICK allele helps maintain high milk yield, especially at higher temperatures where normal cattle show a decline.
• The SLICK allele causes milk yield to decrease proportionally with increasing temperature.

Compare gene editing and selective breeding as methods for introducing a desirable allele (like SLICK for heat tolerance) into a cattle population (like Holstein Friesians). Which statement accurately describes a difference between these methods?

• Selective breeding targets only the specific gene of interest, while gene editing affects many genes.
• Both methods guarantee that all offspring will inherit the desired allele in the first generation.
• Gene editing directly modifies the gene in cells/embryos in a lab, while selective breeding relies on choosing parents with desired traits for mating over generations.
• Selective breeding is much faster, achieving the desired outcome in one generation, unlike gene editing.
• Gene editing inevitably reduces overall genetic variation more than selective breeding.

Complete the sentence about evolutionary relationships: Closely related species tend to share more ______ in their DNA nucleotide sequences compared to more distantly related species.

• introns
• mutations (or similarities/identities)
• stop codons
• differences
• telomeres

Which type of nucleic acid is particularly useful for tracing maternal lineage because it is inherited maternally and is generally unaffected by recombination during meiosis?

• Ribosomal RNA (rRNA)
• Nuclear DNA (autosomes)
• Transfer RNA (tRNA)
• Mitochondrial DNA (mtDNA)
• Y chromosome DNA

What bioinformatics tool allows researchers to predict the amino acid sequences of proteins?

• Microarray analysis
• DNA sequencing databases combined with knowledge of the genetic code
• Karyotyping
• Polymerase Chain Reaction (PCR)
• Gel electrophoresis

What technology can be used to simultaneously detect the presence and relative abundance of many different mRNA molecules in a sample, providing a snapshot of gene expression?

• Electron microscopy
• DNA fingerprinting
• Microarray analysis
• Amino acid sequencing
• Northern blotting

In a respirometer experiment measuring oxygen consumption by germinating peas, what is the function of including potassium hydroxide (KOH) solution?

• To provide oxygen for respiration.
• To absorb the carbon dioxide produced during respiration.
• To maintain a constant temperature.
• To absorb excess water vapour.
• To act as a catalyst for respiration.

When setting up a respirometer experiment to investigate the effect of temperature, why is it important to include a control respirometer (e.g., containing dead peas or glass beads)?

• To measure the rate of photosynthesis.
• To ensure the equipment is properly sealed.
• To account for any changes in gas volume due to temperature or atmospheric pressure fluctuations not caused by respiration.
• To provide a baseline for oxygen production.
• To absorb the carbon dioxide produced by the apparatus itself.

Why should a respirometer apparatus be left in the water bath for a period (e.g., five minutes) before starting measurements?

• To allow the peas to start respiring aerobically.
• To ensure the potassium hydroxide solution is fully saturated.
• To allow the temperature of the apparatus and its contents to equilibrate with the water bath temperature.
• To remove all oxygen from the apparatus before starting.
• To check for leaks in the system by observing initial pressure changes.

A graph of respiration rate (measured by O₂ consumption) versus temperature for germinating peas typically shows an increase from 10°C to an optimum around 30°C… Explain the initial increase in rate.

• More ATP is available at higher temperatures.
• Enzymes involved in respiration gain kinetic energy, leading to more frequent successful collisions with substrates.
• The cell membrane becomes more permeable to oxygen at higher temperatures.
• The peas switch from anaerobic to aerobic respiration.
• Carbon dioxide concentration inside the peas increases.

Explain the decrease in respiration rate observed at temperatures significantly above the optimum (e.g., >30-40°C).

• Substrate concentration becomes limiting at high temperatures.
• Oxygen availability decreases sharply above the optimum temperature.
• Enzymes involved in respiration begin to denature, losing their specific 3D structure and active site shape.
• The peas enter a state of dormancy to conserve energy.
• The potassium hydroxide solution stops absorbing carbon dioxide effectively.

In an experiment investigating photosynthesis using isolated chloroplasts and DCPIP (an electron acceptor that changes colour when reduced), why are the chloroplast suspensions kept in the dark before the experiment starts?

• To allow chloroplasts to accumulate CO₂ needed for the experiment.
• To activate the enzymes of the Calvin cycle.
• To prevent the light-dependent reactions from starting and reducing the DCPIP prematurely.
• To allow the thylakoid membranes to become fully permeable.
• To synchronize the chloroplasts’ internal clocks.

In the chloroplast/DCPIP experiment, absorbance decreased over time when illuminated… The rate of decrease was fastest with red light, intermediate with blue, and slowest with green. Explain the difference between red and green light results.

• Green light has higher energy per photon than red light, causing faster reduction.
• Chlorophyll absorbs red light effectively but reflects/transmits most green light; therefore, more photoactivation and electron release occur under red light, reducing DCPIP faster.
• DCPIP absorbs green light more strongly, interfering with the measurement.
• Chlorophyll absorbs green light effectively but red light poorly; therefore, photosynthesis is faster under green light.
• Red light denatures the electron transport chain proteins, while green light does not.

Indicate whether CO₂ concentration, light intensity, and temperature primarily directly affect the Calvin cycle (light-independent reactions) and/or photophosphorylation (part of light-dependent reactions). Which statement is correct regarding direct effects?

• CO₂ concentration directly affects both the Calvin cycle and photophosphorylation.
• Light intensity directly affects the Calvin cycle but not photophosphorylation.
• Temperature directly affects the Calvin cycle and photophosphorylation.
• CO₂ concentration directly affects photophosphorylation but not the Calvin cycle.
• Light intensity directly affects both the Calvin cycle and photophosphorylation.

African giant pouched rats can be trained to detect Mycobacterium tuberculosis by smell. What type of receptor cell allows rats (and humans) to detect chemicals associated with smell and taste?

• Mechanoreceptor
• Photoreceptor
• Thermoreceptor
• Chemoreceptor
• Nociceptor

Rats trained to detect M. tuberculosis might also respond to samples containing other Mycobacterium species. Suggest a reason for this lack of perfect specificity.

• The rats’ sense of smell is generally poor and unreliable.
• Different Mycobacterium species are unrelated and produce entirely different chemicals.
• Closely related species like those within the Mycobacterium genus likely produce some similar volatile organic compounds due to shared metabolic pathways, which stimulate the same olfactory receptors in the rat.
• The training process inadvertently teaches rats to respond to any bacterial sample.
• The other Mycobacterium species mimic the smell of the reward given during training.

Complete the missing taxonomic ranks for the African giant pouched rat, Cricetomys gambianus: Kingdom: Animalia; Phylum: Chordata; Class: Mammalia; Order: ______; Family: ______; Genus: Cricetomys; Species: gambianus.

• Order: Carnivora; Family: Felidae
• Order: Rodentia; Family: Nesomyidae
• Order: Primates; Family: Hominidae
• Order: Rodentia; Family: Muridae
• Order: Artiodactyla; Family: Bovidae

Outline differences (other than membrane-bound organelles) between typical cells of Eukarya and Bacteria. Which comparison is INCORRECT?

• DNA Structure: Eukarya = linear DNA associated with histone proteins; Bacteria = typically circular DNA lacking histones.
• Ribosomes: Eukarya = larger 80S ribosomes in cytoplasm/RER; Bacteria = smaller 70S ribosomes.
• Cell Walls: Eukarya = Present in plants (cellulose) & fungi (chitin), absent in animals; Bacteria = Usually present, contain peptidoglycan.
• Cell Division: Eukarya = Mitosis (nuclear division) and cytokinesis; Bacteria = Binary fission.
• Cell Size: Eukarya = typically 1-5 µm in diameter; Bacteria = typically >10 µm in diameter.

Describe how viruses are classified based on their structure. Which feature is LEAST commonly used for primary classification across all viruses?

• Type of nucleic acid (DNA or RNA).
• Presence or absence of a phospholipid envelope.
• Shape of the protein capsid (e.g., icosahedral, helical).
• Whether the nucleic acid is single-stranded or double-stranded.
• Presence or absence of tail fibres (relevant for bacteriophages but not a universal feature).

In barley seeds, experiments showed blue light inhibits germination compared to darkness. Blue light exposure also increased abscisic acid (ABA) concentration, while ABA levels remained low in the dark. ABA is known to inhibit germination. What is the likely explanation for blue light’s effect?

• Blue light directly destroys the seed embryo.
• Blue light stimulates gibberellin production, which overrides ABA’s effect.
• Blue light increases ABA levels, and this higher ABA concentration inhibits the germination process (possibly by interfering with gibberellin action).
• ABA levels are irrelevant; blue light inhibits germination by damaging photosynthetic pigments.
• Blue light causes dehydration, preventing germination.

Describe and explain the role of auxin in cell elongation. Which step is NOT part of the acid growth hypothesis?

• Auxin binds to specific receptor proteins, often located on the cell surface membrane.
• This binding triggers signalling that activates proton pumps (H+-ATPases) in the plasma membrane, which actively transport H+ ions out of the cytoplasm into the cell wall space.
• The resulting decrease in pH (acidification) in the cell wall activates pH-dependent enzymes called expansins.
• Expansins disrupt hydrogen bonds between cellulose microfibrils and other cell wall polymers, loosening the wall structure.
• Auxin directly enters the nucleus and acts as a catalyst for the synthesis of new cellulose microfibrils.
• With the wall loosened, the cell’s internal turgor pressure causes the cell to take up water by osmosis and stretch or elongate.

Outline the roles of troponin, tropomyosin, actin, and myosin in sarcomere contraction. Which statement accurately describes one of these roles?

• Tropomyosin binds calcium ions, causing it to change shape.
• Actin filaments perform the power stroke, pulling myosin inwards.
• Myosin heads bind to actin, forming cross-bridges, after tropomyosin moves away from the binding sites.
• Troponin directly breaks down ATP to provide energy for contraction.
• Calcium ions bind to myosin heads, causing them to detach from actin.

Succinylcholine is a drug structurally similar to acetylcholine (ACh) used as a muscle relaxant. It binds to ACh receptors at the neuromuscular junction but is not broken down as quickly as ACh. Suggest how it prevents muscle contraction.

• It blocks the release of calcium ions from the sarcoplasmic reticulum.
• It acts as a competitive inhibitor, blocking ACh binding OR binds and causes prolonged depolarization preventing repolarization, thus blocking further action potential generation in the muscle fibre.
• It enhances the breakdown of acetylcholine by acetylcholinesterase.
• It directly prevents myosin heads from binding to actin filaments.
• It stimulates continuous muscle contraction leading to fatigue and relaxation.

Duchenne muscular dystrophy (DMD) is a genetic disease caused by a mutation in a single gene on the X chromosome that affects the protein dystrophin. The allele causing DMD is recessive. Explain why DMD mainly affects boys.

• The gene is located on the Y chromosome, which only boys have.
• Girls have two X chromosomes; if one carries the recessive DMD allele, the dominant allele on the other X chromosome usually masks its effect, making them carriers. Boys have only one X chromosome (XY), so if they inherit the DMD allele on that X, they express the disease as there’s no corresponding allele on the Y.
• The recessive allele is only expressed in the presence of male hormones.
• Boys inherit two copies of the X chromosome, increasing their chances.
• The condition is dominant in boys but recessive in girls.