Practicals.

Question 1

Outline the method of purifying DNA from plant tissue by precipitation - (8 marks)

Answer 1

1. Grind/blend tissue and mix with salt and detergent solution.
2. Place in thermostatically water bath at 60 degrees celsius for 15 minutes.
3. Cool mixture by placing in ice water bath (for 5 minutes).
4. Add protease and alcohol.
5. Add RNAase enzymes (to hydrolyse RNA).
6. Pour (ice) cold ethanol down the side of tube.
7. Remove DNA strands in upper alcohol layer.
8. Use a hook/glass rod to remove DNA.

Question 2

Outline the method of separating DNA from plant tissue by electrophoresis (9 marks)

Answer 2

1. Cut DNA into fragments using restrictive enzymes - endonucleases.
2. Use agarose gel.
3. Use a loading buffer solution.
4. Use a running buffer solution.
5. Use a wide comb to make wells.
6. Load fragments in wells close to the cathode - negative electrode.
7. Load control sample of DNA - DNA ladder.
8. Apply current.
9. Switch off current when buffer has moved to near end of the gel.

Question 3

Outline the method of visualising DNA extracted from a plant tissue (5 marks)

Answer 3

1. Use UV light.
2. Use a fluorescent dye.
3. Southern blotting.
4. Use a nitrocellulose paper, nylon membrane.
5. Fixing band locations by heating to 80 degrees celsius.

Question 4

Describe how to use a sphygmomanometer to measure the blood pressure of a person (9 marks)

Answer 4

1. Use after subject has been seated for 5-10 minutes.
2. Use on upper left, non-dominant arm - place on the brachial artery.
3. Support left arm and no talking or looking at device.
4. Inflate cuff until pressure is sufficient to stop blood flow.
5. Use a stethoscope under the cuff to hear Korotkoff sounds.
6. Slowly, decrease the pressure until no sound is heard.
7. Record reading when first sound is heard and when sounds stop.
8. or record the two values from the digital display if you’re using a digital sphygmomanometer.
9. Sound indicates systolic pressure and absence of sound indicates diastolic pressure.

Question 5

Describe how the students could gather data to compare the stomatal density of plants growing in the woodlands and the grassland habitat.

Answer 5

1. Randomly sample plants from both grassland and woodland.
2. Take leaves from the same species of plants present in both habitats.
3. Collect a minimum of 5 leaf samples (in both habitats).
4. Same position + age of lead on plant.
5. Take impressions of leaf from lower/upper/both/ same surfaces of leaves.
6. View the impressions using same magnification + lens + size of FOV.
7. Count stomata in FOV.
8. Count only whole stomatas.
9. Repeat the same experiment in both habitats - minimum of twice + and calculate mean.
   Hazards + safety + mitigations:
10. Dyes used in leaf impressions can be toxic and irritate the skin and eyes + wear non-latex gloves, lab-coats and safety goggles to prevent contact with skin + eyes.
11. Broken glass can cause cuts -> check equipment for cracks or defects before use and discard damaged glassware safely + use both hands when carrying glassware + use a dustpan and brush to dispose of broken glassware in a sharps container.

Question 6

A student put some seeds on wet cotton wool in a petri dish and left them to germinate. The student counted the number of seeds that had germinated. Describe a method the student could use to find the best or optimum temperature for the germination of seeds (6 marks).

Answer 6

• Maintain water levels by covering dish and repeat watering regularly.
• Use at least 3 dishes per temperature with minimum of 5 seeds per dish.
• Optimum temperature would have most number of seeds germinated - record at which temperature most seeds germinated and the temperature where seeds germinated the fastest.
  Control:
• Repeat experiment near the optimum temperature.
• Keep the volume of water constant, keep volume of oxygen constant, keep humidity constant, keep the type + variety + mass + size + age of seed constant, keep pH constant.
  Safety:
• Wear non-latex gloves when handling petri dish to avoid contamination.

Question 7

Measuring resting pulse rate? (7)

Answer 7

1. Rest for 10 minutes to determine resting HR.
2. Exercise if you’re determining exercise HR.
3. Patient in sitting position.
4. Measuring pulse from the wrist -> place the index and middle finger over the underside of the opposite wrist, below the base of the thumb.
5. Press firmly with flat fingers until you feel the pulse.
6. Once you find the pulse, count the beats for 10 seconds then multiply by 6 or count for 30 seconds and multiply by 2.
7. Repeat 3 times and take a mean -> Increased reliability.

Question 8

Investigating effect of exercise and pulse rate.

Answer 8

1. IV:
   - age
   - gender
   - BMI
   - diet
   - training programme.
2. DV:
   - Heart rate in bpm.
   Control:
   - age,
   - gender,
   - diet,
   - level or intensity of training
   - previous physical activity level,
   - BMI
3. Health + safety:
   - Ensure no subject has serious health concerns - asthma.
4. Processing Data:
   - Calculate mean -> reduces effect of any anamalous results.
   - Calculate standard deviation -> assess reliability of data -> Size of the SD indicates spread of data about the mean -> Smaller SD = more reliable + precise data.
   - Use SD to calculate standard error -> to plot error bards on appropriate graph -> SD/square root of (n)
   - Calculate t-test -> to determine if there is a significant different between the mean values for each IV category -> if t-calculated > t-critical then reject the null hypothesis and accept the alternate hypothesis - there is a significant difference between the two mean values.
   if t-critical > t-calculated, then accept the null hypothesis -> No significant difference beween the two mean values and any differences between the two means is due to chance.

Question 9

Electrocardiogram - ECG? (5)

Answer 9

1. ECGs measure spread of electrical excitation through the heart.
2. Process = electrocardiography.
3. Doesn’t directly measure electrical activity of the heart but measures small electrical differences in skin which occur as a result of the electrical activity of the heart.
4. Results can be monitored on computer screen or printed out.
5. Changes in peaks can be used to detect and diagnose heart conditions.

Question 10

Risks of electrocardiogram?

Answer 10

1. Generally no risks.
2. Procedure monitors electrical impuleses and does not emit electricity.
3. No risk of shock.
4. However, during exercise ECG, some patients may experience arrhythmias (heartbeat with irregular rhythm) or heart distress.

Question 11

Performing Cardiopulmonary Resuscitation (CPR). (14)

Answer 11

Chest Compressions:
1. Check airways for breathing by tilting head back.
2. Carry out chest compressions (on adult).
3. Place the heel of your hand on the sternum at the centre of the person’s chest.
4. Place your other hand on top of your hand and interlock your fingers.
5. Using your body weight, keep your elbows locked straight + press straight down vertically using your body weight.
6. Press down firmly + quickly by 4-5 cm then relax. Allow the chest to come back up fully again - this is one compression.
7. After each compression, release all pressure on the person’s chest without losing contact between the hands and the sternum.
8. Aim to do the chest compressions at a rate of 100-120 compressions a minute - the speed of the song “staying alive.”
9. Repeat x30 then give mouth-to-mouth resuscitation (expired air resuscitation) twice.
Rescue breaths - Expired Air resuscitation.
10. Pinch the person’s nostrils closed with your thumb and forefinger (to prevent air escaping).
11. Make a complete seal over their mouth with your mouth.
12. Exhale gently into their mouth and watch to ensure their chest rises. If it does, don’t tilt the head back, try again and recheck for obstructions.
13. If the chest does rise, blow gently until chest rises, then remove your mouth and watch the chest fall. Give a second rescue breath, then check for a pulse. If there is a pulse, continue with rescue breaths.
14. Repeat this on a 30:20 ration until an ambulance arrives.

Question 12

Assisting someone having a heart attack. (6)

Answer 12

1. Call 999 - Inform ambulance control that it is a suspected heart attack - raises priority in the list.
2. Try to make the person rest while waiting for an ambulance -> avoids unnecessary strain on the heart.
3. Sit person on W position -> Sit up at about 75 degrees to the ground with knees bent.
4. Give person 300mg of aspirin -> Provided no allergies and above 16 years of age.
5. If person has medication for angina - help them to take that.
6. Monitor constantly, record breathing, and pulse rate until ambulance or assistance arrives.

Question 13

Using a defibrillator?

Answer 13

1. Use an automated external defibrillator (AED) -> safe, portable, and electrical device.
2. AED helps establish a regular heartbeat during cardiac arrest by monitoring person’s heartbeat and giving them an electric shock if necessary.
3. Apply two electrode pads to an exposed chest.
4. Pads placed in diagonal line across chest with heart position in the middle.
5. Reading on the machine shows if heart is defibrillating.
6. If it is, the AED applies electrical discharge -> electrical shock.
7. This stops the chaotic electrical activity of fibrillation + allows heart to restore regular rhythm determined by SAN.

Question 14

Treating respiratory arrest? (5)

Answer 14

1. Call for help
   - If you’re alone, call for help and for an ambulance.
   - If avaliable, wear gloves and mask to protect you + the patient.
2. Open their airways.
   - Carefully roll the person on their back.
   - If they’re unresponsive, open their airways + remove any obstruction visible in the mouth (using a sweeping motion of your finger).
   - Place one hand on the casualty’s forehead and two fingers under their chin. Gently tilt their head back and lift the chin. Move their tongue from the back of the throat.
3. Check their breathing.
   - Maintain the head tilt and chin lift and look for chest movement. Listen for sounds of normal breathing and see if you can feel their breaths on your cheek.
4. Provide rescue breaths (expired air resuscitation).
   - Pinch the person’s nostrils closed with your thumb and forefinger (to prevent air escaping).
   - Make a complete seal over their mouth with your mouth.
   - Exhale gently into their mouth and watch to ensure their chest rises. If it does, don’t tilt the head back, try again and recheck for obstructions.
   - If the chest does rise, blow gently until chest rises, then remove your mouth and watch the chest fall. Give a second rescue breath, then check for a pulse. If there is a pulse, continue with rescue breaths.
5. Carry out CPR.
   - In the absence of a pulse, you must carry out cardiopulmonary resuscitation (CPR).
   - CPR involves both chest compressions and rescue breaths to keep their heart and circulation going.
   - If they start breathing normally again, stop CPR and put them in the recovery position.