OCR A Level Biology B (Advancing) Scientific literacy in biology June 2025 question paper H422/02

This question is based on the Advance Notice Article ‘Dormancy in cereals: not too much, not too little’.

The article describes dormancy in cereal seeds, such as barley.

The diagram shows a drawing of a cross section through a barley seed.

State the name of the structure labelled A in the diagram and state its function.

Outline how the structure labelled B is formed and state its function.

The article describes how the hormones ABA and GA regulate seed dormancy.

Suggest how removal of the structure labelled C can reduce seed dormancy.

Outline an experimental plan to investigate the effect of temperature on the germination of barley seeds.

You do not need to include a risk assessment or details of apparatus in your answer.

State two environmental factors, other than temperature and oxygen concentration, that affect germination in barley seeds.

Seed dormancy is usually the result of seeds being exposed to a period of cold.

State the name of another process in plants that requires exposure to a period of cold.

Dormancy in cereal seeds is important in agriculture.

Explain one advantage for farmers of dormancy in cereal seeds.

Flooding of fields can lead to barley seeds failing to germinate, whereas rice seeds do germinate in flooded fields. Farmers often sow rice seeds in flooded fields.

Use the information in the article to explain why rice seeds do germinate in flooded fields but barley seeds do not.

A student uses a potometer to calculate the rate of transpiration of different species of plant.

The potometer used by the student is shown in the diagram.

The movement of the air bubble was measured using a ruler with a mm scale.

In an initial experiment, the student obtains these results for one species of plant:

Position of bubble at start = 2 mm Position of bubble after 10 minutes = 117 mm Distance moved by the bubble = 115 mm

Calculate the percentage error in the results.

* Blood clotting is an essential process that protects against excessive bleeding when a blood vessel is damaged.

Describe the mechanism of blood clotting and suggest why a small amount of initial damage can lead to a relatively large and rapid response.

Extra answer space if required.

Styptic pencils can be used to stop bleeding from minor cuts, such as cuts from shaving.

A styptic pencil is a stick of hydrated salt, which acts as a vasoconstrictor and also stimulates clumping of blood proteins.

Suggest how a styptic pencil stops bleeding at the site of a cut.

The intracellular enzyme lactate dehydrogenase (LDH) can be used to diagnose tissue damage caused by injury or disease.

Explain how analysis of LDH in a blood sample can be used to assess the severity of tissue damage.

This is a photomicrograph of a section of mouse pancreas.

Identify the structures labelled F and G.

F........

G........

Glycosylated haemoglobin (HbA1c) is used to monitor how well a patient’s diabetes is controlled.

HbA1c was traditionally measured as a percentage, but it is now measured in mmol mol^–1, which is the amount of glucose (in mmol) per mole of haemoglobin.

A patient was told that their HbA1c was 42 mmol mol^–1.

They found a table of HbA1c values used in diagnosis.

The equation can be used to convert values in % to mmol mol^–1. (i)

HbA1c (mmol mol^–1) = (HbA1c (%) – 2.14) × 10.929

Calculate the patient’s HbA1c concentration in %.

Give your answer to 2 significant figures.

Use your answer to part (i) to determine the status of the patient, based on the values in the table.

* Semaglutide is a new form of anti-diabetes medication that is prescribed as a once-weekly injection for treatment of Type 2 diabetes.

Clinical trials have shown that semaglutide causes a significant reduction in HbA1c and body mass compared with existing treatments, such as daily insulin injections and other anti-diabetic drug treatments.

Other clinical trials have shown that semaglutide causes a significant reduction in kidney damage but a significant increase in retina damage compared with placebos.

Evaluate the potential advantages and disadvantages of semaglutide for treatment of Type 2 diabetes.

Extra answer space if required.

Solar farms use solar panels to generate electricity from sunlight. In the UK, solar farms range in size from 0.3 to 1 km² and are usually located on agricultural land.

Some people are concerned about the environmental impact of solar farms, particularly when agricultural land is converted into a solar farm.

A study in the USA examined the biodiversity of a solar farm over a period of five years.

Construction of the solar farm was completed in 2017.

Scientists monitored the biodiversity of the plant species in the solar farm each year from 2018 to 2022 and used Simpson’s Index of Diversity (D) to compare biodiversity over the study period.

The table shows the results for 2018 and 2022.

Use the data in the table to calculate D for 2022.

The scientists concluded that the biodiversity had increased from 2018 to 2022.

Explain whether your value for D supports this conclusion.

Suggest what additional information would be needed to increase the confidence in this conclusion.

In the same study, the scientists compared the biodiversity of insect species in the solar farm and in two parts of an adjacent field that was growing soybean crops throughout the study period.

Their results are shown in the table.

Explain the results shown in the table.

A student stated:

‘The main challenge for agriculture in the future is that climate change will have a worse effect on crop plants than it will on weed species.’

Suggest and explain whether the student’s statement is likely to be correct.

The hormones that control gametogenesis have different roles in males and females.

State the role of luteinising hormone (LH) in males and in females.

Explain why follicle stimulating hormone (FSH) is often used to treat infertility in women.

The light microscope image shows a section through part of a human ovary.

Identify the structures labelled H, J and K.

Outline the formation of secondary oocytes from oogonia.

The most common cause of Down’s syndrome is trisomy 21, which results in three copies of chromosome 21 being present in the cells of an affected individual.

Describe how trisomy 21 occurs.

Describe one other way in which Down’s syndrome can be caused.

The risk of having a child with Down’s syndrome increases with the mother’s age.

Suggest and explain a reason for this.

Describe two ways in which an older couple can reduce the risk of having a child with Down’s syndrome.

Identify one ethical issue associated with either of your answers to part (ii).

In 1952, Erwin Chargaff published a paper showing the composition of DNA bases in many species.

The paper formed the basis of what are now known as Chargaff’s rules.

The table shows some of the data from Chargaff’s original paper.

Use data from the table for human, maize and E. coli DNA to explain the basis of Chargaff’s rules.

PhiX174 is a virus that has single-stranded DNA and does not obey Chargaff’s rules.

Suggest an explanation for PhiX174 not obeying Chargaff’s rules.

A group of students extract DNA from peas.

This is the method they use:

1. Blend 100 cm³ peas with 2 g table salt and 100 cm³ cold water.

2. Strain through a mesh and collect the liquid portion (the homogenate) in a beaker.

3. Allow to settle for 10 minutes.

4. Transfer to several test tubes.

5. Slowly pour ethanol into each tube to form a layer on top of the homogenate.

6. Use a glass rod to collect the DNA that clumps where the layers meet.

Suggest modifications to the procedure that would:

• reduce damage to the DNA by enzymes

• increase the release of DNA from cells after step 2

• remove histones from DNA after step 4.

Reduce damage to DNA by enzymes........

Increase release of DNA from cells........

Remove histones from DNA........

One student places the ethanol in a water bath at 50 °C before using it in step 5.

The student is unable to collect any DNA.

The student carries out some research online. They find a publication that investigated the effect of temperature on the concentration of DNA remaining in solution when ethanol was added.

The results are shown in the graph.

Use the data in the graph to explain why the student was unable to collect any DNA.

The table compares the structure of DNA and RNA nucleotides.

Complete the table by writing the names of the structural features present in DNA and RNA.

A section of RNA is represented in the diagram.

Draw a circle around a phosphodiester bond.

Answer on the diagram.

Complete the following passage using the most appropriate words or phrases.

Semi-conservative replication of DNA involves the enzyme........,

which breaks the........ bonds between the two strands.

DNA nucleotides bind to each of the separated strands and the enzyme

........ joins the nucleotides in a

........ reaction to form two new strands.

Describe the role of cell cycle checkpoints in ensuring the accuracy of DNA replication.

Suggest why mutations that affect cell cycle checkpoints can increase the general rate of mutation.

Radiotherapy causes damage to the DNA of cancer cells.

Suggest how this process can reduce the size of a tumour.

Umbilical cord blood can be collected from the placenta after birth.

Umbilical cord blood transplantation can be used as an alternative to bone marrow transplantation.

Suggest the type of potency for the stem cells present in umbilical cord blood.

Suggest one advantage of umbilical cord blood transplantation over bone marrow transplantation.