2012 PMS Mock 2012 Solutions (1).doc

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Mock Examination, 2012

HUMAN BIOLOGICAL

SCIENCES

STAGE 3

SOLUTIONS

1. B2. D3. A

4. A5. A6. C7. D8. B9. A

10. C11. D12. D13. A14. A15. B16. D17. A18. C19. A20. D21. C22. A23. B24. A

25. D26. C27. C28. B29. D30. A


2/10

31. [13 marks]

(a) (i) Trigger ovulation / conversion of follicle to corpus luteum (1)

(ii) Initiates uterine contractions during labour/release of milk (1)

(b) (i) LH is released under the influence of releasing factors from thehypothalamus (1) LH produced in anterior lobe of pituitary (1)

(ii) Oxytocin is produced by in the hypothalamus (1)Oxytocin released from the posterior lobe of pituitary (1)

(c) Increased thyroxine levels (1) or decreased TSHRF levels (1) or decreasedTSH levels (1) Any two = 2 marks

(d) Surgery (1) to remove a portion of thyroid gland (1) ORRadioactive iodine (1) to kill portion of thyroid tissue (1)

(e) Steroid hormones pass through membranes (1) and affect the activity ofgene/DNA (0.5)Protein hormones bind to cell membrane (1) to release an enzyme the affectsprotein production at ribosomes(0.5)

32. [11 marks]

(a) Increases glucose levels (1)

(b) Promotes the conversion of glycogen to glucose / glycogenolysis (1)Promotes the conversion of proteins to glucose / gluconeogenesis (1)(Accept: lypogenesis (1))

(c) Elevated glucose and insulin levels (1);

Type 2 Diabetes controlled by modifying diet to decrease sugars (or WTTE)(1)

(d) Genetic Engineering:The modification of the DNA (1)Uses a bacteria/plasmid (1)Production of protein (1) 3 marks

Gene Therapy:Replacement of faulty gene(s) with useful gene from healthy cell /AW (1)Uses patients own cells (1)

Production of genetically modified cells / modified virus are re-introduced intopatient / virus infects cells(1) 3 marks


3/10

33.

(a) (i) Oral administration of drug will produce more muscle protein thanintravenous administration (1) or vica verca

(ii) Mode of administration (1)(iii) Amount of muscle protein (1)

(b) Correctly constructs axes using appropriate scale (Muscle protein on Y axis,Time on X axis) (1)Correctly plots points and joins points to form a line (ruler) (1)Labelling of axes with correct name and unit (1)Identifies lines using key/labels (0.5)

Title appropriate with both variables included and the two groups(experimental and control) (0.5)(Max: 2 marks if bar graph drawn)

(c) Intravenous administration will produce more muscle protein over 9 / 12months than oral administration (1)

(d) Increase reliability (1) avoid results of the effect due to error, chance orvariation (1)

(e) Criticism: Differences in conditions such as diet, exerciseProgrammes and facilities may affect the result

Any two = 2 marksImprovement: Each city should contain two groups (1)

One group treated with oral drug and the other group withintravenous injections (1)

34.

(a) Plasma Cells: produce antibodies (1)Memory Cells: recognise original invading antigen and initiate / produce a

quicker stronger immune response upon next / subsequent /secondary infection (1)Antigen: substance capable of producing an immune response(1)Helper T-Cells: attract cells such as phagocytes and macrophages / cause

lymphocytes to become sensitised / intensify phagocytic activity(1)

(b)Axes labelled (1)

Antibody A B A=vaccination B=infection (1)

production Correct shape (1)


4/10

Time (days)

(c) Use a deactivated pathogen (1) Dead pathogen (1) (A: microorganism)

Use part of a pathogen (1)Use deactivated / inactivated toxoid (1)Use DNA components / Modified DNA of pathogen / Living attenuatedpathogens (1) Any two = 2 marks

(d) Vaccines may require animal testing (1). Vaccines may be tested on human populations in developing countries (1)

Vaccines are produced using animal embryos (1)Vaccines may require cells of tissues of aborted human foetuses (e.g. rubella)(1)Vaccines cultured in animal tissue may have a risk of infection from possible

unknown viruses (1)

Any two = 2 marks

35.

(a) Founder effect (1) the founding population on the islands had anunrepresentative low frequency of the HLA 27 allele (1)

(b) Genetic Drift (1) variation due to random, chance events (1)

(c) In heterozygotes (0.5), the allele (0.5) for sickle cell anaemia provides aselective advantage (0.5) against malaria (0.5)

(d) Fossil evidence: For some groups of species there is a sequence of structuralchange (1) OR simple species are found in deeper stratawhilst complex species are more recent (1) OR the existenceof transitional species (1)

Protein analysis: Similar species show greater similarity in protein structurethan species that are not closely related (1)

Homologous structures: In some groups of species there are structures thatshow variation from a common, basic form that relate,such as vertebrate pentadactyl limb (1)

(Accept examples that illustrate the answer)36.

(a) Transition from reliance on sense of smell to reliance on sense of sight /reduced sense of smell and increased sense of sight (1)

(b) The face becomes flatter (1)Less prognothism (1)


5/10

Eyes forward facing (1)

(c) Loss of brow ridge due to development of forehead/frontal lobe (1)Development of rounded cranium due to increased cranial capacity/frontallobe (1)Increased cranial capacity due to increased cerebrum (1)Reduced teeth size due to increase in dietary meat (1)Mandible is less robust due to decreased teeth size/ bipedal adaptation (1)(or other suitable answer)More forward facing eye sockets due to increased stereoscopic vision (1)Any three = 3 marks

37.

(a) Dry cave deposit (1)Soft parts decay leaving hard parts undisturbed (1)Rapid burial (1) in dry, alkaline soils (1)Organic matter removed and replaced by inorganic salts / calcification(1)

Any two points = 2 marks

(b) Earthquakes (1) Tidal waves (1) Folding/faulting (1) Erosion (1) Transport byrivers/scavengers (1)

Any 2 = 2 marks

(c) Absolute Dating: Carbon / Radiometric Dating (1)Measure C14:C12 ratio in fossils/charcoal deposits(1)Determine number of half-lives (1)Multiply by half-life: 5,730 yrs (1)

Any 3 = 3 marks

Relative Dating: Fluorine analysis (1)Measure fluorine content (1)Fluorine ions in water replace the minerals in the bone (1)The older fossil will contain more fluorine (1)ORStratigraphy (1)Determine depths of fossils (1)The older fossil will be deeper (1)

38.(a) A: Central canal/medullary cavity / Haversian canal (1)

B: Periosteum (1)


6/10

(b) C: Blood supply/provision of requirements and removal of wastes(1) / linkslamellae / osteocytes allows materials to be exchanged

D: Repair/maintenance of bone (1)

(c) Lamellae / bony matrix (1)Protein matrix with inorganic salts, mainly calcium (1)

(d) Osteoporosis produces brittle bones (1)Bones develop pores/paces (1)

Diet includes calcium / Treated with diet supplements containing calcium /Named dairy products (1)Load bearing exercise is recommended (1)

Hormone replacement therapy (1) Any 2 = 2 marks

(e) (idea that) bones fused together (1)by fibrous connective tissue (1)Examples include: teeth in jaw, facial bones, cranial bones, sacral/coccyx,

pelvic bones (1 example = 1 mark)

39.

(a) Dendrite (1)Receive information and carry it towards cell body (1)

(b) Unipolar / Cell body located adjacent /to the side of nerve fibre (1)

Cell body in found in dorsal root ganglion (1)

(c) Stimulus: Low pH detected (No mark Given information in question)Receptor: Detected by chemoreceptors in the aortic and carotid bodies (1)

and (to a lesser extent) in medulla oblongata(1)Modulator: Impulses sent to the respiratory centre (0.5) in the medulla

oblongata (0.5)Sends impulses down the sympathetic nerves / via phrenic nerve/

intercostal nerve (1)Effector: Increased activity of diaphragm/intercostal muscles (1)Also increase activity of SA node (1) to increase heart rate (1)

Response: Decreased CO2 concentration / increased pH (0.5)

Negative feedback (0.5) Decreased breathing rate (1) and heart rate (1) /Breathing rate / heart rate return to normal. (1)

Any five = 5 marks in a logical, sequenced order.

(d) Stimulus:Body fluid decreases /osmotic pressure increases (1)Receptors: Osmoreceptors in thirst centre (0.5) of hypothalamus (0.5) detect

change


7/10

Modulator:Nervous stimulation creates dry throat / thirst sensation/ makesperson feel thirsty(0.5)

Effector/Response: Athlete will drink (0.5)

Answer must show a logical, sequenced order.

SECTION 3

40.

(a) Transcription The process by which the messenger RNA (mRNA) (0.5) is formed using

the code in the DNA molecule (0.5)

Occurs in the nucleus (1)

DNA unwinds to expose the segment of DNA/gene to be transcribed (A:

copied) (1)

RNA polymerase joins complimentary mRNA bases to the DNA (1)

Uracil replaces Thymine in the mRNA chain (1)

mRNA molecule undergoes modification / introns are removed leaving just

the exons (1)

(DNA reassembles) and mRNA moves out of nucleus through nuclearpores into the cytoplasm (1)Any five = 5 marks in an ordered, logical sequence (e.g. in the nucleusmay not be the first point made. The candidate may end by saying thisoccurs in the nucleus. However, answer must show understanding ofwhere the process occurs, the processes involved and the main moleculesinvolved )

Translation

The production of a protein using the information that is coded in themRNA molecule (1)

mRNA attaches to a ribosome (1)

Ribosomes read the mRNA (in the cytoplasm) (1)

For each sets of three bases (codon) (0.5) on the mRNA there is a

complementary transfer RNA (tRNA) anticodon (0.5)

Base pairing C-G, U to A (1)

tRNA with the complementary anticodon brings the correct amino acid to

the chain (1)

The amino acid in the chain form bonds resulting in a chain of amino acids

/ polypeptide / protein (1)


8/10

This process is repeated to make many protein molecules dependent upon

the gene that is transcribed (1)

Any five = 5 marks in an ordered, logical sequence (e.g. in the nucleusmay not be the first point made. The candidate may end by saying this

occurs in the nucleus. However, answer must show understanding ofwhere the process occurs, the processes involved and the main moleculesinvolved )

(b) Genetic Probe:

Determine sequence of gene of interest (1)

Produce a complimentary strand of DNA/RNA (1)

Label this with fluorescence or radioactive label (1)

Introduce to DNA to be tested so that it will attach to gene of interest (1)

Any three points = 3 marks

Used to identify a gene/allele / successful gene transfer (1)

To establish relationships/ presence of inheritable diseases (1)

PCR:

Denaturing of the DNA /Heat DNA to separate strands (1)

Annealing (0.5) to introduce a primer (0.5) / Primer introduced/attached to

DNA strand (1)

Elongation (0.5) Use of TAQ-polymerase / heat stable DNA polymerase to

synthesise a new DNA strands (0.5)

Repeat the process (1)


To produce large amounts of DNA (1)

For investigation, experimentation and/or other DNA techniques (1)

41.

(a)

Stimulus causes depolarisation of membrane (1) as

Na + moves into cell and K+ moves out (1)

Sodium-potassium pump restores resting membrane potential/switched off

(1)

This is repolarisation (1)

There is a short refractory period after stimulation (1)

During which the membrane will not respond to stimulus (1)


9/10

Diagram (1)

These changes depolarise adjacent membrane and the process repeats

itself along the axon (1)

At the motor end plate (1)

Neurotransmitters released (1)

Such as noradrenalin and ACh (1)

These are released from vesicles (0.5) into the synaptic cleft (0.5)

They diffuse/move across this cleft (1)

and bind to receptors on muscle (1)

(b) Alzheimers disease:

Loss in total number of cerebral neurons (1)

Loss in number of dendritic connections between cerebral neurons (1)

Patients experience memory loss / confusion / mood swings / aggression /

general withdrawal (1)

Patients experience difficulty with processing information and making

decisions / Dopamine regulation disturbed (1)

4 points for 4 marks

Obtain stem cells from embryo or adult bone marrow (1)

These are multi/pluripotent (1)

Treat stem cells with chemicals to establish them as neurons (1)

Introduce these cells into patient brains (1)


42.

(a)

Short, wide pelvis/sacrum (1) to support abdominal organs and support a

carrying angle at the knees/muscle attachment for gluteals (1)

Pelvis tilts forward (1) to help create lumbar curve (1)

Impact of acetabulum effecting carrying angle /Carrying angle of knees (1) so

they sit directly under midline of the body (1)

Long femurs (1) allow an energy efficient long stride length/lower centre of

gravity (1)

Large medial condyles at knee (1) account for carrying angle/ load bearing (1)

Two arches present in foot (longitudinal and transverse) (1) to allow smooth

transfer of weight from heel to toe and spring when pushing off (1)


10/10

Non-opposable and large first digit (big toe) (1) to push off and increase

stability (1)

Robust tarsals (1) for load bearing (1)

Any four pairs = 8 marks

Bipedalism allowed for free hands (1) OR mobility of digits increased as did

ability to manipulate (1) AND

Corresponding increase in cranial size (1)

(b)

A population of australopithecine multiplied and spread over large territory (1)

A geographic barrier developed (mountain range, water body) (1)

Separated one population into two populations (1) and

Prevented gene flow (1)

Different populations experienced different selective pressures (1)

And different mutations (1)

Different features were selected (1) Populations accumulated differences and became reproductively isolated

to become two distinct species (1)

Any six points = 6 marks

(c)

Development of tool culture / Acheulian or Hand Axe Industry (1)

Greater variety in diet, including meat (1)

Use of fire (1)

Use of constructed shelter (1)

Greater development of speech communication (1)

Cooperative hunting (1)

Greater group numbers (1)

Any four points = 4 marks

2012 PMS Mock 2012 Solutions (1).doc

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