Comprehensive Biology & Biotechnology Lecture Review

150 question-and-answer flashcards covering experimental design, cell biology, genetics, reproduction, biotechnology, immunology, pathogens, epidemiology, physiology, plant and animal homeostasis, and related concepts from the lecture notes.

What is an independent variable in an experiment?

A variable that is deliberately controlled or manipulated by the researcher.

Define dependent variable.

The variable that is measured and may change in response to the independent variable.

What is a controlled variable?

A factor kept constant throughout an investigation to ensure a fair test.

Differentiate between nominal and ordinal qualitative variables.

Nominal variables have no intrinsic order (e.g., eye colour) whereas ordinal variables have a meaningful order or ranking (e.g., mild, moderate, severe).

Distinguish discrete from continuous quantitative variables.

Discrete variables take only whole-number values, while continuous variables allow any numeric value within a range (e.g., mass, pH).

What does validity measure in an experiment?

Whether the investigation actually tests the stated hypothesis and produces relevant data.

How is reliability improved in scientific experiments?

By repeating trials and averaging results to obtain consistent findings.

Define systematic error and provide two main types.

A repeatable error affecting every measurement equally; includes selection bias and measurement bias.

What causes random errors?

Unpredictable variations between or within measurements due to factors like environmental fluctuations.

What is accuracy in scientific measurement?

The closeness of obtained values to the true value, improved by minimising systematic errors.

Define precision in measurements.

The ability to obtain consistent repeated measurements, improved by minimising random errors.

Name three prokaryotic groups of organisms.

Bacteria, archaea, and (some classifications of) protists such as algae.

Give two examples of eukaryotic unicellular organisms.

Amoeba and certain protozoa (e.g., Plasmodium spp.).

Why are viruses considered non-living?

They cannot reproduce or carry out metabolism without infecting a host cell.

State one advantage of asexual reproduction.

It requires less energy and only one parent, enabling rapid population growth in stable environments.

State one disadvantage of sexual reproduction.

It is energy-intensive because organisms must find mates and often synchronise reproductive cycles.

Define gamete.

A specialised sex cell (sperm or egg) produced by organisms for sexual reproduction.

What is a zygote?

The diploid cell formed after fusion of two haploid gametes during fertilisation.

Differentiate external and internal fertilisation.

External fertilisation occurs outside the bodies of parents (often in water), whereas internal fertilisation occurs inside the female's body.

Why must many aquatic species release large numbers of gametes?

External fertilisation has a low probability of gamete union, so producing many gametes increases success chances.

Define pollination in flowering plants.

The transfer of pollen from anthers to the stigma of a flower.

What structure grows after pollination to enable fertilisation in plants?

The pollen tube grows down the style to deliver sperm nuclei to the ovule.

What is binary fission?

A form of asexual reproduction in prokaryotes where the cell duplicates DNA and divides into two identical daughter cells.

Describe vegetative propagation.

Asexual reproduction in plants where new individuals arise from roots, stems, or leaves (e.g., runners, suckers).

What are spores and which kingdoms commonly produce them?

Haploid, often unicellular reproductive units produced in large numbers by fungi and some plants for dispersal.

Name the hormone secreted by the corpus luteum that maintains the uterine lining.

Progesterone.

Which pituitary hormone triggers ovulation?

Luteinising hormone (LH).

What hormone is released by the blastocyst to maintain the corpus luteum?

Human chorionic gonadotropin (HCG).

Explain positive feedback using childbirth.

Uterine contractions stimulate oxytocin release, which intensifies contractions, further increasing oxytocin until birth occurs.

List the phases of the cell cycle in order.

G1, S (DNA synthesis), G2, mitosis, cytokinesis.

What is the primary outcome of mitosis?

Two genetically identical diploid daughter cells for growth and repair.

What is crossing over and when does it occur?

Exchange of genetic material between homologous chromosomes during prophase I of meiosis, generating variation.

Define independent assortment.

Random orientation of homologous chromosome pairs in metaphase I (and chromatids in metaphase II) of meiosis, contributing to genetic diversity.

Compare the chromosome number of meiosis products to the parent cell.

Meiosis produces four haploid cells, each with half the chromosome number of the diploid parent.

Describe the structure of DNA.

A double helix of antiparallel strands made of nucleotides with a sugar-phosphate backbone and complementary base pairing (A-T, C-G).

What enzyme unwinds DNA during replication?

DNA helicase.

What is the role of DNA ligase?

It seals nicks in the sugar-phosphate backbone, joining Okazaki fragments on the lagging strand.

Distinguish between leading and lagging strands.

Leading strand is synthesised continuously toward the replication fork; lagging strand is synthesised discontinuously away as Okazaki fragments.

What is transcription?

The process where RNA polymerase synthesises mRNA from a DNA template inside the nucleus.

Define codon.

A sequence of three mRNA bases that specifies a particular amino acid.

What molecule carries amino acids to the ribosome?

tRNA (transfer RNA).

Name the start codon in mRNA.

AUG (codes for methionine).

What is epigenetics?

Heritable changes in gene expression without alteration of DNA sequence (e.g., DNA methylation, histone modification).

Differentiate exons and introns.

Exons are coding DNA sequences that remain in mRNA; introns are non-coding sequences removed during mRNA processing.

Give two structural differences between prokaryotic and eukaryotic DNA.

Prokaryotic DNA is circular and not nucleus-bound; eukaryotic DNA is linear, wound around histones, and housed in a nucleus.

What are plasmids?

Small, circular, non-chromosomal DNA molecules in prokaryotes that often carry advantageous genes (e.g., antibiotic resistance).

Define gene pool.

The total collection of genes and their alleles within a population.

What is genetic drift?

Random changes in allele frequencies due to chance events, especially in small populations.

Explain the bottleneck effect.

A drastic population reduction that randomly alters allele frequencies and reduces genetic diversity.

What is the purpose of PCR?

To amplify specific DNA segments, producing millions of copies for analysis.

Who developed the Sanger method of DNA sequencing?

Frederick Sanger.

Define recombinant DNA.

DNA formed by joining genetic material from two or more different sources.

What is a transgenic organism?

An organism whose genome has been altered to include DNA from another species.

Give an agricultural example of a transgenic crop.

Bt cotton produces bacterial toxin genes that kill caterpillar pests.

Name a common selectable marker used in plasmid cloning.

Antibiotic resistance gene.

State one ethical concern of DNA profiling.

Privacy and ownership of individuals' genetic information.

Differentiate selective breeding from genetic engineering.

Selective breeding chooses parent organisms to mate naturally; genetic engineering directly alters DNA to introduce traits.

What does the term ‘vector’ mean in biotechnology?

A DNA molecule (e.g., plasmid or virus) used to deliver foreign genetic material into a host cell.

Define mutagen.

An agent, such as radiation or chemicals, that causes changes in DNA sequence.

Name three types of point mutations.

Substitution, insertion, deletion.

What is a frameshift mutation?

Insertion or deletion of bases that shifts the mRNA reading frame, altering downstream amino acid sequence.

Define aneuploidy.

The presence of an abnormal number of chromosomes in a cell (e.g., trisomy 21).

What is polyploidy?

Having more than two complete sets of chromosomes (common in plants, often lethal in humans).

Describe Koch’s first postulate.

The suspected pathogen must be present in every case of the disease but absent from healthy organisms.

What discovery is Louis Pasteur famous for regarding disease?

Proposing the germ theory and developing pasteurisation to kill microbes.

Name three modes of pathogen transmission.

Direct contact, indirect contact via fomites or airborne droplets, and vector transmission.

Give an example of a viral disease transmitted by vectors.

Dengue fever transmitted by Aedes mosquitoes.

What is an opportunistic fungal infection?

A fungal disease that primarily affects individuals with weakened immune systems (e.g., thrush).

Define antigen.

A molecule capable of triggering an immune response by binding to specific receptors on lymphocytes.

Which leukocytes are primarily responsible for phagocytosis?

Neutrophils and macrophages.

What is the complement system?

A cascade of plasma proteins that enhances antibody action and phagocytosis against pathogens.

Differentiate innate and adaptive immunity.

Innate immunity is non-specific and present from birth; adaptive immunity is specific, involving B and T lymphocytes, with memory.

What class of antibody is most abundant in blood?

IgG.

Describe the role of helper T cells.

They activate B cells, cytotoxic T cells, and macrophages by releasing cytokines after recognising antigens.

What is herd immunity?

Population-level protection that arises when a high percentage of individuals are immune, interrupting pathogen spread.

State two symptoms typical of inflammation.

Redness and swelling (also heat and pain).

Which hormone regulates blood glucose by stimulating cellular uptake of glucose?

Insulin.

How do endotherms primarily generate body heat?

Through metabolic processes within their own tissues.

Give one structural adaptation for cold environments in endotherms.

Thick fur or blubber for insulation.

What is vasodilation and why is it important?

Widening of blood vessels near the skin to increase heat loss when body temperature rises.

Explain osmoregulation in plants.

Controlling water balance via structures like stomata closure and waxy cuticles to reduce transpiration.

Identify the main nitrogenous waste removed by kidneys.

Urea (from amino acid breakdown).

Briefly describe haemodialysis.

Blood is pumped through a machine with a semi-permeable membrane to remove wastes before returning to the body.

Name one limitation of haemodialysis.

Requires frequent clinic visits and carries infection risk.

What part of the eye primarily refracts incoming light?

The cornea (about 80% of light refraction).

Which visual disorder is corrected with concave lenses?

Myopia (short-sightedness).

What happens to the lens during accommodation for near vision?

Ciliary muscles contract, suspensory ligaments slacken, and the lens thickens to increase refractive power.

How do cochlear implants restore hearing?

They convert sound into electrical impulses that directly stimulate the auditory nerve, bypassing damaged hair cells.

Define epidemiology.

The study of the distribution, causes, and control of diseases in populations.

Differentiate incidence from prevalence.

Incidence is new cases over time; prevalence is total existing cases at a specific time.

What is a cohort study?

An observational study following two similar groups differing in exposure to determine disease outcomes over time.

Why was plain cigarette packaging introduced?

To reduce smoking by removing branding appeal and adding health warnings.

Explain the concept of genetic engineering for disease prevention using HPV vaccine.

Recombinant technology produces viral protein antigens that safely elicit immunity against HPV, preventing cervical cancer.

What is PCR annealing?

Primers bind to complementary DNA sequences around 60 °C, enabling DNA polymerase extension.

Give one advantage of artificial insemination in agriculture.

Allows rapid dissemination of desirable genetics to many females without transporting the male.

Define SCNT (somatic cell nuclear transfer).

A cloning method where the nucleus of a somatic cell is transferred into an enucleated egg to develop a clone.

Why can overuse of cloning reduce biodiversity?

It propagates identical genotypes, decreasing genetic variation in the population.

State one benefit of golden rice.

Provides beta-carotene to combat vitamin A deficiency in regions reliant on rice.

What enzyme is commonly used to cut DNA at specific sequences?

Restriction endonucleases.

Describe gel electrophoresis.

Technique that separates DNA fragments by size as they migrate through agarose gel under an electric field.