IB Biology Practice Question (core)

Outline natural methods of cloning in some eukaryotes

a. clones are genetically identical organisms OR group of cells derived from a single parent cell b. asexual reproduction in plants such as tubers/runners/bulbs Allow other verifiable examples of plants c. common in non-vertebrates such as budding in hydra Allow other verifiable examples of invertebrates d. budding in yeast/fungi Allow other verifiable examples of fungi e. identical twins «in humans» are clones because they originate fromthe same cell

What were the outcomes of the human genome project?

a. complete human DNA/chromosomes sequenced; b. identification of all human genes / find position/map (all) human genes; c. find/discover protein structures/functions; d. find evidence for evolutionary relationships/human origins/ancestors; e. find mutations/base substitutions/single nucleotide polymorphisms; f. find genes causing/increasing chance of/develop test for/screen for diseases; g. develop new drugs (based on base sequences) / new gene therapies; h. tailor medication to individual genetic variation / pharmacogenomics; i. promote international co-operation/global endeavours;

An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.

a. higher temperatures so more transpiration/droughts/dehydration/water shortage b. more forest fires c. more/new pests/diseases because of the changed conditions d. competition from trees/plants «that colonize/spread to boreal forests» e. trees/«named» organisms «of boreal forests» not adapted to warmer conditions OR trees/«named» organisms migrate/change their distribution due to warmer conditions f. trees die so loss of habitat for animals g. faster decomposition/nutrient cycling «so conditions in the ecosystem change» h. standing water/floods due to more snow/permafrost melting

Compare and contrast cis-fatty acids and trans-fatty acids.

- both are unsaturated fatty acids both have two carbon atoms joined by a double bond - in cis-fatty acids the two H atoms are on the same side while in trans-fatty acids they are on opposite sides cis-fatty acids are healthier than trans-fatty acids cis-fatty acids have a lower boiling/melting point than trans cis-fatty acids have a kink «in the chain» but trans do not

Describe how the structures of starch molecules are related to their functions

Helical/spherical shape to compact Large/ insoluble so osmotically inactive Branched so glucose is released for respiration Large so cannot leave cell

Sickle-cell anemia affects the ability of red blood cells to transport oxygen.Explain the consequence of the mutation causing sickle-cell anemia in relation to the processes of transcription and translation.

caused by single base substitution (mutation); mutation in gene coding for (one of) polypeptide chain in hemoglobin/HbA; GAG (on sense strand of DNA) mutated to GTG; when transcribed, RNA sequence/codon becomes GUG rather than GAG; during translation, have one amino acid substituted for another; causes glutamic acid/glutamate to be replaced by valine; change alters folding of Hb protein/makes RBCs sickle-shaped (in low oxygen); sickle shaped cells block capillaries/cause tissue damage and pain;

Explain how the cell cycle is controlled.

cell cycle is a sequence of stages / cell cycle is G1, S, G2 and mitosis (control of the cell cycle) by cyclins/cyclin levels of cyclins rise (and fall)/fluctuate during the cell cycle/surge at different times/have to reach a certain concentration conditions inside as well as outside the cell affect regulation four cyclins/different cyclins to enter different stages of/events in the cell cycle / cyclins regulate the sequence/timing of the cell cycle / cyclins trigger the next stages The idea of different cyclins acting at different phases must be clear. cyclin-dependent kinases / cyclins bind to kinases and activate them kinases phosphorylate other proteins phosphorylated proteins perform specific functions in the cell cycle

Outline the roles bacteria play in the carbon cycle.

decomposition of dead organic material «by saprotrophic bacteria» «decomposition» leads to CO2 formation/regeneration due to respiration «saprotrophic bacteria only» partially decompose dead organic matter in acidic/anaerobic conditions in waterlogged soil results in peat formation in bogs/swamps photosynthetic bacteria/cyanobacteria fix CO2 in photosynthesis

Explain the processes that control changes in ventilation rate during exercise.

exercise increases aerobic respiration; CO2 concentration in blood increases; drop in pH of blood detected / blood more acidic; breathing centres send impulses to diaphragm and intercostal muscles; increase rate of contraction; increase in ventilation rate increases oxygen uptake/decreases CO2;

Describe the process of peat formation

formed from dead plant material/leaves/mosses/Sphagnum formed in waterlogged sites/bogs/mires/swamps where bacteria/fungi/saprotrophs are not active/are inhibited organic matter not fully decomposed «occurs» in acidic conditions «occurs» in anaerobic conditions Reject anaerobic respiration «very» slow process/takes a long time

Explain non-competitive inhibition

inhibitor binds to enzyme at different location than active site; this causes a change in the shape/conformational change of active site; thus preventing the substrate from binding to the active site / resulting in a decrease of enzyme activity/speed of reaction;

A species is often defined as a group of similar individuals that interbreed in nature and produce fertile offspring. Discuss some problems with the use of this definition.

not all organisms can be defined in this way / does not take into account hybrids/ microorganisms/plants; (even if able to interbreed) may have differences in DNA/protein; does not apply to bacteria/other organisms that reproduce asexually; in sympatric/allopatric isolation members of the same species do not interbreed; (in some species) significant differences in morphology can occur within the same species eg: sexual dimorphism/metamorphosis/ring species;

Identify two hydrolysis reactions that occur in the small intestine.

polysaccharides to disaccharides /monosaccharides OR starch/glycogen to maltose sucrose to glucose AND fructose maltose to glucose lactose to glucose AND galactose proteins/peptides/polypeptides to shorter peptides/amino acids OR dipeptides to amino acids triglycerides/lipids/fats/oils to glycerol AND fatty acids

Explain 2 benefits of having strongly acidic conditions in your digestive system

provides ideal pH for stomach enzyme activity (acidic conditions) denature proteins /start breakdown of other organicsubstances (acidic conditions) convert pepsinogen (inactive) into pepsin (acidic conditions) destroy pathogens in ingested food

Outline the structure of a ribosome?

small subunit and large subunit; mRNA binding site on small subunit; three tRNA binding sites / A, P and E tRNA binding sites; protein and RNA composition (in both subunits);

Define the term passive immunity.

the acquisition of antibodies from another organism

Define osmolarity

«measurement of» solute concentration of a solution

State one difference between the proteins produced by free ribosomes and those produced by ribosomes attached to the endoplasmic reticulum

free ribosomes synthesize proteins for use within the cell / cytoplasm attached ribosomes produce proteins for export / use within lysosomes / membranes

Explain the significance of polar amino acids and non-polar amino acids in membranes.

non-polar amino acids for hydrophobic part of the bilipid layer; polar amino acids are soluble/have stable interactions in water/extracellular fluid/cytoplasm; non-polar amino acids are soluble/have stable interactions in the lipid bilayer; polar amino acids strongly hydrophilic and non-polar amino acids are repelled by water/are hydrophobic; polar amino acids allow hydrophilic channels; (help to) retain protein in position in the membrane; polar amino acids form hydrophilic channels/protein pores in membranes; transmembrane proteins have polar amino acids on either side of the membrane; integral proteins are held in place by polar amino acids;

Explain how the surface area to volume ratio influences cell sizes

small cells have larger ratio (than larger cells) / ratio decreases as size increases; surface area / membrane must be large enough to absorb nutrients / oxygen / substances needed; surface area / membrane must be large enough to excrete / pass out waste products; need for materials is determined by (cell) volume; cell size is limited (by SA / vol ratio) / cells divide when they reach a certain size; reference to diffusion across / through membrane / surface area;

Describe the importance of stem cells in differentiation.

stem cells are undifferentiated cells; embryo cells are stem cells; stem cells can differentiate in many/all ways / are pluripotent/totipotent; differentiation involves expressing some genes but not others; stem cells can be used to repair/replace tissues/heal wounds;

Define tidal volume and ventilation

tidal volume: volume of air taken in with each inhalation/out with each exhalation; ventilation rate: number of inhalations/exhalations/breaths per minute

Water has important solvent properties. Explain these properties using an example to illustrate your answer

water molecule is polar OR water has «weak» positive and negative charges substances that dissolve in water are hydrophilic water forms hydrogen bonds with polar substances positive/hydrogen side/pole of water attracted to negative ions OR negative/oxygen side/pole attracted to positive ions e.glucose/other example dissolves because it is polar OR sodium chloride/other example dissolves because ions are attracted to water

Explain how meiosis promotes variation

(in prophase I) crossing over/chiasmata formation (between homologous chromosomes) random alignment of homologues/bivalents in metaphase I / independent assortment of homologues / chromosomes; second division of meiosis separates alleles further (random orientation of chromatids/chromosomes in metaphase 2) combinations of alleles in gametes is unlimited/2n;

Outline the process of endocytosis. (5 marks)

(plasma) membrane encloses/engulfs solid particles/droplets of fluid/molecules; fluidity of the membrane allows endocytosis; (plasma) membrane forms pit/forms indentation/pulled inwards/invaginates; membrane pinches off /seals back on itself/edges fuse; vesicle/vacuole formed; inside of plasma membrane becomes outside of vesicle membrane / converse; vesicle breaks away from plasma membrane/moves into cytoplasm; active process / endocytosis/vesicle formation requires energy; vesicles carry material to plasma membrane; vesicle fuses with membrane; (by joining of) phospholipid bilayers;

Outline the metabolic processes that occur in starchy seeds during germination.

.water absorbed by the seed / seed rehydrated; water activates metabolism gibberellin synthesized/produced/secreted; gibberellin stimulates the production of amylase; amylase digests/hydrolyses starch to maltose; maltose converted/hydrolysed to glucose (by maltase); glucose used in aerobic respiration; glucose used in synthesis/production of cellulose;

Outline the role of tRNA activating enzyme

ATP «hydrolysis»provides energy for amino acid attachment they attach a specificamino acid to the (3') end / free CCA of a tRNA they do this repeatedly / they attach amino acid to all of the tRNA molecules that have anticodon corresponding to that amino acid

Explain the role of protein pumps and ATP in active transport across membranes.

Active transport is the passage of materials against a concentration gradient (from low to high) This process requires the use of protein pumps which use the energy from ATP to translocate the molecules against the gradient The hydrolysis of ATP causes a conformational change in the protein pump resulting in the forced movement of the substance Protein pumps are specific for a given molecule, allowing for movement to be regulated (e.g. to maintain chemical or electrical gradients) An example of an active transport mechanism is the Na+/K+ pump which is involved in the generation of nerve impulses

Discuss the advantages and disadvantages of using rats as models in this investigation.

Advantages: - small size - easy to look after in research labs - short lifespan - study can extend over several generations - can be killed «to get experimental results» if benefits of research justify it - «mammalian» so similarities with humans - fewer ethical objections than if humans are used/not ethical to subject humans to hypoxia/does not cause harm to humans Disadvantages: - ethical objections/ wrong to cause suffering to animals/rats - rat physiology/anatomy not same as human

Explain how aphid stylets can be used to study the movement of solutes in plant tissues

Aphids tap into phloem with their stylets to use sap as a food source Plants grown in radioactive CO2/ 14CO2 incorporate it into carbohydrate Phloem contents/sap/fluid flows through the stylet 8 Aphid body severed/cut from stylet «after stylet inserted into phloem» Analyze «sap/fluid exuded from stylet» for solutes/carbohydrates OR Radioactive-labelled carbon can be detected «in the phloem sap» Stylets at different parts of the plant can show sequence/rate of movement

Discuss the benefits and dangers of vaccinations

Benefits: [4 max] immunity results can limit pandemics/epidemics/spread of (infectious) diseases; diseases can be eradicated/smallpox eliminated; reduces mortality/deaths due to disease; can protect vulnerable groups/young/old/with other conditions; decrease crippling effects of diseases (such as polio); decreased health care costs; Dangers: [4 max] may produce (mild) symptoms of the disease; human error in preparation/storage/administration of vaccine; individual may react badly to vaccine / defective immune system / hypersensitive/allergic reaction; immunity may not be life-long/booster required; possible toxic effects of mercury-based preservatives/thimerosal;

What is essential for diffusion?

Concentration gradient

Distinguish between transcription and translation

DNA is transcribed AND mRNA is translated transcription produces RNA AND translation produces polypeptide/protein RNA polymerase used in only in transcription and ribosomes only intranslation transcription in the nucleus «of eukaryotes» and translation in the cytoplasm tRNA needed for translation but not transcription nucleotides linked in transcription and amino acids in translation OR sugar-phosphate/phosphodiester bonds in transcription and peptide bonds in translation

Compare and Contrast the Davson Danielli and Singer-Nicholson models of cell membrane and describe the evidence that disproves the Davson-Danielli model. (4 marks)

Davson Danielli model of the plasma membrane describes a phospholipid bilayer that lie between two layers of globular protein but after research it was proved wrong, there are not two layers of globular proteins. The Singer-Nicholson fluid mosaic model; free to move. Membrane proteins were found to be very varied in size.

What is the function of tRNA

Each carries a specific amino acid/ has an anticodon: 3 bases on tRNA bind to 3 bases on mRNA/ codon and anticodon interaction tRNA attaches to ribosomes/ holds amino acids in place

Explain how the structure and properties of phospholipids help to maintain the structure of cell membrane.

Hydrophilic head /hydrophobic tail -head made from glycerol and phosphate -tail made from two fatty acids -saturated/unsaturated fatty acid in tail - Arrangment in the membrane like phospholipids foriming a bilayer -Heads facing outside the membrane -Hydrophobic interior, hydrophilic exterior of membrane-fluidity helps membrane to be stable-hydrophilic and hydrophobic restrict entrance of substances

Explain how the units maximum volume of air exhaled in one second (VE1) as a percentage of the maximum volume of air inhaled (VI) used to measure lung function are useful in showing if a person suffers from asthma.

asthma causes constriction/congestion/inflammation of the airways/breathing tubes/bronchi/bronchioles; units measure ability to exhale quickly/efficiently which could indicate asthma;

Use the diagram to explain why sucrose is classified as a carbohydrate

It contains the elements carbon, hydrogen + oxygen in 2:1 ratio/ same proportions as in water

Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis.

Phospholipids in membranes are fluid, so membranes can change shape that would otherwise be impossible if they were solid. The fluidity allows vesicles to be pinched off from membranes or fuse with them In endocytosis, part of the plasma membrane is pulled in and fluid becomes enclosed when a vesicle is pinched off so they can move through cytoplasm In exocytosis, vesicles fuse with plasma membrane and contents are expelled, the membrane flattens out again.

State the composition and the function of the plant cell wall (2 marks)

Plant cell wall is made of cellulose. It consists of three layers:middle lamella, primary cell wall, plasma membrane. The function is to give shape or protection. Also, maintain turgor pressure.

Compare the DNA found in prokaryotes + eukaryotes:

Prokaryotes: - Circular - In cytoplasm - Naked - Plasmids Eukaryotes: - Linear - Enclosed in a nuclear membrane - Associated with proteins/ histones - No plasmids Both prokaryotic + eukaryotic DNA consist of a double helix of nucleotides, phosphates + bases

Which two molecules are the principal components of membranes?

Protein and lipids

Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane.

Proteins are synthesized by ribosomes and enter the rER. Vesicles bud off from the rER and carry proteins to the Golgi. The Golgi modifies proteins, and then the vesicles bud off from the Golgi and carry modified proteins to the plasma membrane.

Describe passive transport across a biological membrane. (5 marks)

Requires no energy Goes with the concentration gradient Water is moved by osmosis small uncharged molecule moved by simple diffusion charged molecules moved by facilitated diffusion

What is facilitated diffusion?

The passive movement of a particle across a cell membrane via a channel protein.

Describe the process of active transport.

The process of active transport happens when the energy from the hydrolysis of ATP to pump molecules against the concentration gradient.

List the functions of membrane proteins.

Transport: Protein channels (facilitated) and protein pumps (active) Receptors: Peptide-based hormones (insulin, glucagon, etc.) Anchorage: Cytoskeleton attachments and extracellular matrix Cell recognition: MHC proteins and antigens Intercellular joinings: Tight junctions and plasmodesmata Enzymatic activity: Metabolic pathways (e.g. electron transport chain)

Describe the process involved in blood clotting

cells/tissue is damaged/cut/bruised; damaged cells/platelets release clotting factors; (clotting factors cause the) production of thrombin; blood plasma contains soluble fibrinogen; fibrinogen converted into fibrin; by thrombin; forms a net of fibres trapping blood cells; forming a clot / prevents blood loss / entry of bacteria/pathogens; cascade of reactions/series of stages prevent accidental clotting/speed up clotting;

Outline how the structure of cellulose makes it suitable as a component of cell walls

chains of glucose/1-4 glycosidic linkages/covalent bonding between glucose beta glucose so alternating orientation of glucose units OR beta glucose forms straight chains forms microfibrils/long and thin/thin fibres/parallel bundles of cellulose molecules OR hydrogen bonding/cross linkage between cellulose molecules holds them together high tensile strength/rigid/doesn't stretch so provides support/allows turgidity

Explain cladistics as a method of classifying organisms

cladistics uses cladograms/tree diagrams; show clades/branches (in parallel) that begin at a point/node; each clade includes a (common) ancestral organism/node and all its descendents; members of a clade share derived/inherited characteristics; clades are nested/subsets of larger clades; cladograms show evolutionary history/origin of organisms / phylogeny; branch length (of clade) can indicate (relative) amount of genetic change/time; clades based on (objective) molecular analysis/genetic evidence / differ in amino acid sequences/DNA base changes/mutations; fewest number of differences/maximum parsimony determines branch separation; predictability of DNA base changes/mutation rates suggests evolutionary timelines; problems arise when gene change varies (greatly) from one gene to the next; cladograms may not match traditional/Linnaean classification; (mismatch) prompts re-examination of data / reclassification of a group;

Hydrogen bonds can exist both within and between molecules in living organisms and have an impact on their structure and function. Explain the importance of hydrogen bonding for living organisms

cohesion in water/water molecules stick together (due to hydrogen bonds) cohesion helps transport under tension of water/sap in xylem / transpiration stream adhesion between water and cell walls/cellulose/polar molecules adhesion/capillary action helps water to rise in plants/stems/xylem / helps keep leafwalls moist solvent properties (due to hydrogen bonds) with polar/hydrophilic molecules solvent properties exemplified by glucose/other example of a polar solute high latent heat of evaporation / (much) energy required for evaporation so wateruseful as coolant/for sweating high (specific) heat capacity so water temperature changes less base pairing between bases/nucleotides/strands in DNA by hydrogen bonding base pairing between bases in RNA and DNA for transcription/between codon andanticodon for translation proteins have hydrogen bonding in secondary structure/α helix/β pleated sheet proteins have hydrogen bonding between R groups/in tertiary structure/to maintainconformation habitats because water is liquid due to high boiling point/due to water freezing on thesurface habitats on water surface due to surface tension

DNA in chromosomes undergoes replication before mitosis. Outline how complementary base pairing is important in this process.

conservation of the base sequence of DNA; adenine pairs with thymine and cytosine pairs with guanine; (do not accept initials only) both (daughter) cells/DNA strands produced have identical genetic information;

Outline the use of defibrillation to treat life-threatening cardiac conditions

defibrillator is electrodes/a metal paddle/pad that is placed on thepatient's chest the device determines whether fibrillation is happening a series of electrical shocks are delivered through the electrodes electrical impulse is used to depolarize the heart muscle to re-establish the function of the SA node/natural pacemaker/naturalrhythm «of the heart»

Hypertension has been suggested as a possible cause of CHD. Explain the possible causes of hypertension.

deposition of fat in arteries thus losing elasticity/forming fibrous tissues deposition of fat/formation of plaque in arteries thus narrowing oflumen/causing a blockage high salt levels in diets thus retaining more fluids smoking because nicotine is a vasoconstrictor molecule prolonged high levels of stress thus causing vasoconstriction / exposure tostress hormones genetic predisposition makes it more likely that other factors will lead to hypertension

Compare and contrast the structure of a typical prokaryote cell with that of a mitochondrion

differences prokaryote has cell wall but mitochondrion does not mitochondrion has double membrane whereas prokaryote has single membrane OR «Gram negative» bacteria have cell wall between two membranes whereas mitochondria has intermembrane space between two membranes mitochondrion has cristae/invaginations of inner membrane but prokaryote does not OR prokaryote «may have» flagella/pili/«slime» capsule which mitochondria do not have similarities 70S ribosomes in both DNA in both / loop of DNA in both / naked DNA in both shape similar/both rod shaped OR size of both is similar/both about 3 μm long both are membrane-bound

Explain the change in the tidal volume during exercise.

exercise increases / results in higher rate of respiration exercise produces more carbon dioxide / consumes more oxygen increased tidal volume excretes more carbon dioxide / obtains more oxygen increased tidal volume increases gas exchange «across alveoli» concentration gradient«s» of gases is maintained

Outline how Hershey and Chase's experiment provided evidence for DNA as the genetic material

experiment is meant to determine whether DNA or protein is the genetic material viruses/bacteriophages grown in radioactiveS/ S35which enters the protein coat viruses/bacteriophages grown in radioactive P/P32 which enters the DNA «radioactive»viral DNA entered the bacterial cell during infection OR «radioactive»viral protein did not enter the bacterial cell during infection

Explain how flowering is controlled in long-day and short-day plants.

flowering affected by light phytochrome exists in two (interconvertible) forms/Pfr and Pr Pr (red absorbing/660 nm) converted to Pfr (far-red/730 nm absorbing) in red or day light sunlight contains more red than far red light so Pfr predominates during the day gradual reversion of Pfr to Pr occurs in darkness Pfr is active form / Pr is inactive form;in long-day plants, flowering induced by dark periods shorter than a critical length / occurs when day is longer than a critical length enough Pfr remains in long-day plants at end of short nights to stimulate flowering Pfr acts as promoter of flowering in long-day plants short-day plants induced to flower by dark periods longer than a critical length/days shorter than a critical value at end of long nights enough Pfr has been converted to Pr to allow flowering to occur Pfr acts as inhibitor of flowering in short-day plants

Outline relationship between genes, polypeptides + enzymes

gene is a sequence of DNA bases; DNA/gene codes for a specific sequence of amino acids/polypeptide; enzymes are proteins/composed of polypetides; sequence of amino acids determines tertiary structure/folding/shape of active site; change in the gene/mutation will affect the active site/function of an enzyme; enzymes are involved in replication/transcription of genes; enzymes are involved in synthesis of polypeptides;

Predict the effects of global warming on aerobic respiration in fish.

higher temperature, more oxygen consumption «more oxygen consumption» is due to more respiration/metabolism less oxygen can dissolve in warmer water so less «aerobic» respiration more carbon dioxide dissolved so less oxygen for respiration

Outline principles of immunity

immunity is the ability of an organism to resist infection; due to presence of (specific) antibodies; immunity can be active or passive; passive due to receiving antibodies from external sources/across placenta/from breast milk/injection; active results from facing an infection directly/through vaccination; pathogen/foreign cell invades body; leads to clonal selection/formation of B memory cells; B-cells produce specific antibodies; if same pathogen enters body again memory cells activated/stimulated to divide; antibodies produced faster and in greater amounts;

Some proteins in membranes act as enzymes. Describe a model that accounts for the ability of enzymes to catalyse reactions.

induced fit model; (do not accept lock and key hypothesis) accounts for ability of some enzymes to bind to several substrates; enzyme with active site to which substrate(s) binds; enzyme active site and substrate do not match up exactly; enzyme-substrate complex forms; enzyme changes shape once bound / enzyme moulds to substrate/ hand in glove; change in shape strains bonds/facilitates bonds breaking/product formation; reduces activation energy; once reaction is complete, products leave and enzyme can work again;

Outline the stages of the cell cycle.

interphase is the longest phase; interphase includes G1, S and G2; in G1 and G2 /G phases, cell performs normal functions/protein synthesis/cell grows/organelles are replicated; S/synthesis phase when the DNA replicates; mitosis is when nucleus/genetic material divides; named/described stages of mitosis; cytokinesis: the division of the cytoplasm / formation of two daughter cells;

Explain the control of gene expression in eukaryotes.

mRNA conveys genetic information from DNA to the ribosomes «where it guides polypeptide production» gene expression requires the production of specific mRNA «through transcription» most genes are turned off/not being transcribed at any one time/regulated OR some genes are only expressed at certain times some genes are only expressed in certain cells/tissues OR «cell» differentiation involves changes in gene expression transcription factors/proteins can increase/decrease transcription hormones/chemical environment of cell can affect gene expression example of cell environment eg: auxin/insulin/cytoplasmic gradient in embryo transcription factors/proteins may prevent or enhance the binding of RNA polymerase nucleosomes limit access of transcription factors to DNA/regulate gene expression/transcription OR activate or silence genes DNA methylation/acetylation appears to control gene expression «as epigenetic factor» OR methylated genes are silenced «some» DNA methylation patterns are inherited introns may contain positive or negative gene regulators OR gene expression can be regulated by post-transcriptional modification/splicing/mRNA processing

Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.

meiosis reduces a diploid cell into (four) haploid cell(s) (during prophase I) homologous chromosomes pair up/synapsis chromatids (break and) recombine / crossing over (metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell; (anaphase I) (homologous) chromosomes separate and move to opposite poles; (telophase I) chromosomes reach poles and unwind WTTE; (prophase II) chromosomes (condense and) become visible, new spindles form; (metaphase II) chromosomes line up at the centre of the cells/equator; (anaphase II) sister chromatids separate; (telophase II) chromatids reach the poles and unwind

Outline control of metabolic pathways

metabolic pathways can be a sequence/chain of reactions; they can be cycles of reactions; different enzymes control each reaction in the sequence/cycle; accumulation of an end-product can inhibit the first enzyme of the sequence/ pathway; (an end-product inhibitor) joins an allosteric site/a site separate from active site; attachment at the allosteric site changes the shape of the active site; preventing the binding of substrate; until the level of the end-product is reduced (and the inhibition removed); this is an example of negative feedback

Suggest possible reasons for the difficulty of preventing or controlling a viral epidemic in a remote rural region

poor transport infrastructure/poor communication/bad roads/difficult access/no maps/support slow arriving/scattered population poor education/understanding of disease amongst health workers/local population OR continued contact with infected people / other example of unsafe actions more sources of infection such as bats/difficult to find sources of infection lack of/limited access to medical care/doctors/health care workers lack of/no access to/unaffordability of treatment centers/medical supplies/equipment/antivirals/drugs/vaccine/treatments refusal/reluctance in local population to be vaccinated OR difficult to find/reach everyone to vaccinate them/repeat the vaccination migration of people spreads the infection poor sanitation/lack of clean water

Outline reasons for fitting an artificial cardiac pacemaker.

required when rate of heartbeat/heart contraction is too slow/irregular produces electrical impulse that stimulates heartbeat/heart contraction needed when SA node is defective

Suggest a reason for increasing the concentration of sodium-potassium pumps in the membranes of diaphragm muscle fibres

resting potential restored faster increases the «maximum» frequency/rate of contractions OR can contract again sooner

State four glands secreting digestive juices into the alimentary canal.

salivary glands; gastric glands; pancreas; wall of the small intestine;

Discuss the advantages of the production of seeds enclosed in fruits

seeds are protected «inside the fruit» seed dispersal by fruits example of a strategy for seed dispersal by a fruit dispersal reduces competition/spreads seeds away from parent plant/to colonize new areas ✔

State one similarity and one difference between the structure of genes and short tandem repeats.

similarity: both made of DNA/nucleotides OR both have bases/adenine/cytosine/guanine/thymine OR neither has uracil difference: genes are longer/have longer DNA/base sequences «without repeats» OR genes have introns/exons but tandem repeats do not OR genes have base sequences that code for polypeptides/proteins and tandem repeats do no

Describe the features of the alveoli that make them well adapted for gaseous exchange. large SA (to lung)

single cell wall/layer; moist lining; dense network of capillaries; single cell wall to capillary; short distance (for gases to travel)

Describe how Pasteur's experiment provided convincing evidence to falsify the concept of spontaneous generation

spontaneous generation is life appearing from nothing / from non-living / cells only come from pre-existing cells/life broth/culture medium (for bacteria) (used/placed) in flasks broth boiled/sterilized «in some flasks» to kill microbes no clouding/signs of bacterial growth/reproduction / microbes did not appear «in flasks of boiled broth» Allow bacteria or organisms instead of microbes. after necks of flasks were snapped boiled broth became cloudy/growth of microbes because microbes from the air contaminated the «boiled» broth curved necks allowed indirect exposure to air but prevented entry of microbes

Describe the distribution of vascular tissues in the stem of dicotyledonous plants

stem vascular tissue is in bundles «bundles» form a ring phloem is towards outside «of bundle» OR xylem is towards centre «of bundle» ✔

Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA.

strands of DNA (fragments) split/denatured with heat; complementary nucleotides added to split stands (when cooling); with the use of (DNA) polymerase (and primers); process/heating and cooling cycle is repeated (until enough DNA is obtained);

Outline the role of short tandem repeats in DNA profiling.

tandem repeats allow individuals to be distinguished/compared/identified OR tandem repeats are used to identify the source of a DNA sample unique/different number of repeats/combination of tandem repeats in each individual OR unique/different pattern of bands in each individual PCR used for copying/amplifying «tandem repeats» gel electrophoresis used for separation «of tandem repeats»/create pattern of bands

Explain the importance of the surface area to volume ratio as a factor limiting cell size

the rate of material / heat exchange / diffusion is proportional to surface area; the rate of metabolism is proportional to mass / volume; as a cell grows, the volume increases faster than the surface area / as a cell grows, surface area to volume ratio decreases; (without cell division) material / heat cannot be exchanged fast enough to meet the needs of the cell;

State the significance of the statement: p<0.05.

there is a significant «statistical» difference between two experimental values OR there is a less than 5 % chance that the difference is random OR 95 % or more probability that results are due to the experiment «IV» and not random/can reject the null hypothesis OR there is a relationship/correlation between doing exercise and capillary density

Outline transcription in prokaryotes

transcription is the copying of a strand of DNA into RNA/RNA formation; RNA polymerase binds to promoter region of DNA; anti-sense strand as template / only one strand copied; RNA polymerase unwinds DNA/separates the strands; RNA nucleotides/nucleoside triphosphates pair with complementary bases on DNA; Adenine to Thymine, Cytosine to Guanine, and Uracil to Adenine; (do not accept letters alone) added at 3' end / strand grows 5' to 3' ; RNA nucleotides joined with covalent/sugar-phosphate bonds; RNA polymerase separates from DNA when reaches terminator/termination sequence; no introns/post-transcriptional modification/RNA splicing (as occurs in eukaryotes);

State an application of plasmids in biotechnology

transfer/vector of genetic material/genes/DNA fragments OR to produce insulin/useful protein

Outline the law of independent assortment

two «or more»traits/genes are inherited independently of one another observed for traits/genes that are not linked/far apart on the chromosome «due to homologous»chromosomes aligning independently/randomly on equator during metaphase I/meiosis I during anaphase I homologues pulled to separate poles

Some prokaryotes cause infectious disease in humans. Explain the principles of vaccination.

vaccines contain a dead/weakened form of the pathogen/bacteria/virus; vaccine introduced to the body by injection/on surface of skin/orally; antigens in the vaccine cause antibody production; antigen/pathogen engulfed by macrophage/phagocyte; each type of lymphocyte recognizes specific antigen; macrophages activate helper T-cells; which activate B-cells; B-cells divide to form clones/memory cells; B-cells divide to form plasma cells/antibody producing cells; result is (specific) immunity; vaccination/first exposure causes slow production of antibodies and lower level of antibodies; (this idea can be illustrated on a diagram or graph) contact with the disease leads to rapid production and higher level of antibodies; (this idea can be illustrated on a diagram or graph) second/booster shot to stimulate memory cells/more production of antibodies;

Angiospermophyta have vascular tissue (xylem and phloem) that bryophyta lack. Suggest advantages that vascular tissue confers.

would make it easier to stand upright (against gravity)/structural support / allows (angiospermophytes) to be bigger; could put leaves higher in the air to get more sunlight; transport of water supply/nutrients from roots to other tissues; could (more efficiently) transport/translocate sugars/food from leaves for storage;

Suggest a way methylation may affect tumour cell genes

«DNA» methylation may inhibit transcription of genes that would prevent cancer/tumor formation «DNA» methylation may increase mitosis/cell division leading to tumor formation

Some plant families, such as the figwort family, have been reclassified on the basis of evidence from cladistics. Explain the methods that have been used recently to reclassify groups of plants.

«previous» classification used to be based on the appearance/structures of the plant/leaves/flowers/seeds/analogy/phenotype «modern cladistics uses» RNA/DNA nucleotide/base sequencing/amino acid sequencing/homology DNA mutation occurs at a relatively constant rate allowing estimation of when species diverged a shared/common derived characteristic places organisms in the same clade the number of changes in sequences indicates distance from common ancestor OR the fewer the differences «in sequences» means the closer the relationship