Wrong questions bio

Question 1

The geneticist could obtain the HGH gene using any one of three methods.
1.      Use restriction enzymes to cut out a fragment of DNA containing the HGH gene from a human genome.
2.      Convert mRNA for HGH into cDNA using reverse transcriptase.
3.      Create the HGH gene using a ‘gene machine’.
(a)     The geneticist decided not to use restriction enzymes to cut out a fragment of DNA containing the HGH gene from a human genome. She made this decision because only methods 2 and 3 would produce DNA that E. coli could use to make HGH.
Explain why only methods 2 and 3 would produce DNA that E. coli could use to make HGH.

Answer 1

 1.      Human DNA / human gene / HGH gene contains introns
OR
Methods 2 and 3 produce DNA / HGH without introns;
2.      E. coli cannot remove introns / cannot splice mRNA / cannot splice pre-mRNA;

Question 2

     The desired gene in the diagram was from an insect. In stage 6, the plant containing this gene was able to use it to synthesise an insect protein.
The plant is able to synthesise the insect protein. Explain why this is possible

Answer 2

  1.      Genetic code is universal/triplets in DNA always code for same amino acid;
2.      It/insect DNA can be transcribed;
3.      Can be translated (process/mechanism same in all organisms/cells);
2. Accept (basic) transcription (process/mechanism) same in all organisms/cells;

Question 3

Any DNA in the sample is hydrolysed by enzymes before the sample is added to the reaction mixture.

Answer 3

  1.      To remove any DNA present;
2.      As this DNA would be amplified / replicated;

Question 4

Explain the advantage of lipid droplet and Michelle formation

3 marks

Answer 4

1. Droplets increase surface areas (for lipase /
   enzyme action);
2. (So) faster hydrolysis / digestion (of
   triglycerides / lipids);
3. Micelles carry fatty acids and glycerol /
   monoglycerides to / through membrane / to (intestinal epithelial) cell;

Question 5

Describe the role of micelles in the abrosbtpion of fats into the cells lining the ileum

(3 marks but 5 points)

Answer 5

1. Micelles include bile salts and fatty acids;
2. Make the fatty acids (more) soluble in water;
   For ‘fatty acids’ accept fats / lipids.
3. Bring/release/carry fatty acids to cell/lining (of the ileum);
   For ‘fatty acids’ accept fats/lipids.
   4.Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
4. Fatty acids absorbed by diffusion

Question 6

Give one similarity and one difference between a taxis and a tropism.

Answer 6

. Similarity − directional response (to a stimulus) / movement
towards / away from a stimulus;
2. Difference − taxis (whole) organism moves and tropism a growth (response).

Question 7

The use of IPS cells advantages over gene therapy

Answer 7

1. iPS cells) divide;
2. (iPS cells) develop/differentiate into (green sensitive) cones;
   2
   (f) 1. (Use of iPS cells) long-term;
   Accept ‘gene therapy short-term’ or ‘only two years’
   Accept ‘permanent’
3. (Use of iPS cells) less chance of rejection/immune response;
4. (Use of iPS cells) single treatment;
   Accept ‘gene therapy ‘regular/frequent treatment’’
5. Harm/side effects from using viruses (in gene therapy);

Question 8

Something sex linked affects men more than women,
Why

Answer 8

Gene/allele) is on the X chromosome;
2. Females require two alleles/females can be heterozygous/carriers and males require one allele;

Question 10

If the glomerular filtrate of a diabetic person contains a high concentration of glucose, he produces a larger volume of urine. Explain why.

Answer 10

Glucose in filtrate lowers water potential;
Ignore ‘urine’. Accept increase solute potential
Lower Ψ gradient / less difference in Ψ filtrate − Ψ plasma;
Ignore ‘concentration’
Less water reabsorbed by osmosis;

Question 11

Damage to the myelin sheath of neurones can cause muscular paralysis (lines 2-4).
Explain how.

Answer 11

(Refers to) saltatory conduction
OR
(Nerve) impulses/depolarisation/ions pass to other neurones
OR
Depolarisation occurs along whole length (of axon);
Accept suitable description that refers to (transmission) from node to node (of Ranvier).
Accept action potential for depolarisation.
1 and 2. Accept action potentials for impulses.

(Nerve) impulses slowed/stopped;
(Refers to) neuromuscular junction
OR
(Refers to) sarcolemma;

Question 12

synapses ensure that nerve impulses only travel towards the muscle fibre.
Explain how.

Answer 12

NT made in pre synap

Receptors only on the post synapse

Question 13

A woman takes moderate exercise. Explain what causes her heart rate to increase while she exercises.

Answer 13

Rate of resp increases

carbon dioxide concentration increases / pH falls / H+ increases / acidity
increases;
3. chemoreceptors in aortic / carotid bodies / medulla (accept reference to aorta /
carotid arteries not sinus);
4. (impulses to) medulla / cardioaccelerator centre;
5. increased frequency of impulses (award only once);
6. along sympathetic pathway to sinoatrial node / SAN

Question 14

suggest how these two species of palm tree arose by
sympatric speciation.

Answer 14

1. Occurs in the same habitat/environment/population;
2. Mutation/s cause different flowering times;
3. Reproductive separation/isolation
   OR
   No gene flow
   OR
   Gene pools remain separate;
4. Different allele/s passed on/selected OR
   Change in frequency of allele/s;
5. Disruptive (natural) selection;
6. Eventually different species cannot (inter)breed to produce fertile offspring;

Question 15

For inhibiting the enzyme that breaks down acetylcholine why is it good (3m)

Answer 15

Less/no acetylcholine broken down;
2. Acetylcholine attaches to receptors;
3. (More) Na+ enter to reach threshold/for depolarisation/action potential/impulse;

Question 16

how human mass at birth is affected by stabilising selection.

Answer 16

Extreme mass babies least likely to survive (to reproduce) and so less likely to pass on their alleles (for extreme mass at birth);
3. Extreme mass at birth decreases in frequency (in the population)
OR
Alleles (for extreme mass at birth) decrease in frequency (in the population);

Question 17

Describe the structure of the human immunodeficiency virus (HIV).

Answer 17

RNA (as genetic material);
2. Reverse transcriptase;
3. (Protein) capsomeres/capsid; 4. (Phospho)lipid (viral) envelope
OR
Envelope made of membrane; 5. Attachment proteins;

Question 18

Use your knowledge of gas exchange in leaves to explain why plants grown in soil
with very little water grow only slowly.
[2 marks]

Answer 18

Stomata close;
2. Less carbon dioxide (uptake) for less photosynthesis/glucose production;

Question 19

Explain the higher metabolic rate of a small animal eg mouse compared to big animal eg horse

Answer 19

1. (Smaller so) larger surface area to volume ratio;
2. More/faster heat loss (per gram/in relation to body size);
3. (Faster rate of) respiration/metabolism releases heat;

Question 20

Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs.

Answer 20

Renal vein

Vena cava to right atrium;
3. Right ventricle to pulmonary artery

Question 21

Explain how an arteriole can reduce the blood flow into capillaries.

Answer 21

Muscle contracts;
Constricts/narrows arteriole/lumen;

Question 22

Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube.

Answer 22

Sucrose actively transported (into phloem);
OR
More negative water potential;
3. Water moves (into phloem) by osmosis (from xylem);

Question 23

Meiosis results in cells that have the haploid number of chromosomes and show genetic variation. Explain how.

Answer 23

Homologous chromosomes pair up / bivalents form;
Crossing over / chiasmata form;
Produces new combination of alleles;
Chromosomes separate;
At random;
Produces varying combinations of chromosomes / genes / alleles (not twice);
Chromatids separated at meiosis II / later;

Question 24

Suggest two reasons why observed ratios are not often the same as expected ratios

Answer 24

Fertilisation is random
small sample/population
Selection advantage/ disadvantage

Question 25

Explain why it takes longer to obtain a genetic fingerprint if the sample is contaminated

Answer 25

Other DNA is present Need to identify required DNA from the rest

Question 26

Ways PCR differs from DNA replication

Answer 26

Uses heat to separate strands Primer added in PCR, to initiate replication

Question 27

Why are primers required

Answer 27

To allow DNA polymerase to attach and for nucleotides to join

Question 28

Why are two diff primers required

Answer 28

because the sequences at the ends of the target sequence are different / one is at the beginning and one at the end;

Question 29

The DNA probe the genetics used was for an exon in the DNA not an intron. Explain why 3 marks

Answer 29

Introns not translated / not in mRNA / (exons) code for amino acids / introns do not code for amino acids; 2. Mutations of these (exons) affect amino acid sequences (that produce) faulty protein / change tertiary structure of protein; 2. Accept deletion leads to frameshift 3. So important to know if parents’ exons affected, rather than any other part of DNA / introns;