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8a) Deduce and explain the genotype of individual 2.

Classmate ans:
Individual 2 is a female carrier of colour blindness, so her genotype is Bb.
This is because she and individual 1 gave birth to a female with colour blindness. The allele for colour blindness of individuals must come from at least one of her parents. As she is female, she must receive one colour blind X allele from her dad and one colour blind X allele from her mum, to be colour blind. If the allele from her mum is not colour blind, then she would not be colour blind as no colour blindness is a dominant phenotype. Therefore individual 2 must possess heterozygous alleles.

Suggested ans:
Individual 2 must be heterozygous for this trait.
Individual 5, her daughter, is colourblind.
Being a recessive trait, the allele for colour blindness must come from both parents.
One of the alleles for this trait must come from her mother, individual Z.
Being normal herself, she must also have a normal allele.
Therefore, individual 2 must be heterozygous.

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4(d) new drugs have recently become available for treating influenza. One type is the neuraminidase inhibitor. Describe how this type of drug would act as a treatment for influenza.

Candidate answer: Such a drug can inhibit the function of neuraminidase. without neuraminidase the surface membrane of the epithelial cells will remain intact and the virus will remain in the cell. This can reduce the spread of the influenza virus and let the body's own immune response kill the virus more efficiently.

Missing keyword?: Enzyme-substrate complex.

Suggested answer: The neuraminidase inhibitor can bind to neuraminidase. They act as inhibiters by forming an enzyme-substrate complex with them and not allowing them to perform their original function. This can prevent the neuraminidase from releasing virus from the cells as it is inhibited from breaking down molecules.

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3ai) Describe how the muscles in the stomach are involved in food digestion and releasing food into the duodenum in a healthy person.

Candidate answer:
After receiving the food bolt from the oesophagus, the stomach will churn and the food substances can be further broken down into smaller molecules. The food is then passed to duodenum to neutralise and nutrients of the food can be absorbed.

Wrong concept:
1. Not responding the question because she does not include the working mechanism of the stomach muscles.

Suggested answer:
The muscles in the stomach contract and relax to churn food into chyme to increase surface area for easier digestion. There are two sphincter in the stomach that contract and relax to allow food into and out of the stomach into the duodenum.

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3 i) suggest how the blockage of the pancreatic duct affects the digestion of the food.

Classmate ans:
Pancreatic duct secretes pancreatic amylase lipase and protease which are enzymes that catalyse the breakdown of proteins. The blockage prevents secretion of the enzymes, and digestion of food is affected because the food cannot be broken down with these enzymes.the food will still be in a complex form cannot be broken down to simplest form for absorption.

Suggested answer:
Pancreas produce and secrete pancreatic juice that contains lipase, carbohydrase that digests carbohydrates, lipids and proteins into smaller molecules. The blockage of the duct prevents the pancreatic juice from being released to the duodenum  for  digestion. Therefore it affects the digestion of food

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Question 3a(ii): Suggest why patients with gastroparesis may suffer from malnutrition.

Classmate answer: As the patient always feel full after eating only a small amount of food, and the food may even vomit undigested. Therefore, the food substance is not small enough to be absorbed in small intestine and so nutrients in food cannot be absorbed.

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Describe how T cells recognise and respond to the swine influenza virus.

Classmate's answer:
The antigen-bearing cells are detected by T lymphocytes. It will breakdown into killer T cells to kill the pathogens, helper T cells to bind the pathogens together for phagocytosis and memory T cells to recognise the pathogens when it enters the body again.

Wrong wordings:
-detect
-breakdown

Suggested changes:
Detect --> recognise
Breakdown --> differentiate

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Q6a.
Which field required the addition of N fertiliser to achieve the optimal yield? Explain your answer.

Classmate answer:
Field B, as its amount harvested is same with the amount harvested in plot without N fertiliser.

Suggested answer:
Field A, since the plot without N fertiliser in field A cannot achieve the optimal yield, while that in field B can achieve the optimal yield. Moreover, two fields have the identical soil condition. Therefore, field A needs additional N fertiliser.

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Q4cii
Describe how B cells respond to the swine influenza virus.

Classmate answer：
B cells would differentiate into memory cell and plasma cell which producenthe specific antibody to destory thr influenza virus.

Wrong concepts：
1. Did not elaborate the part about memory cell

Suggested answer：
B cells will differentiate into plasma cells which produce antibodies to fight against thr disease. It also produces memory B cells so that large amount of antibodies csn be produced quickly when there is a second time of similar virus infection.

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Q3bii. After the pills are taken into the body, the capsules do not dissolve until the pills have passed through the stomach. Suggest why this is important for th function of the digestive enzymes inside.

Classmate's answer:
The digestive enzymes will digest the proteins in the oesophagus, and the tissue of the oesophagus will then be destroyed. So it is important for the capsule to dissolve until it passes through stomach to prevent demage to other parts of the body.

Wrong concept:
Will not digest the proteins in the oesophagus

Suggested answer:
Digestive enzymes are proteins. They can be broken down by proteases in the stomach. The capsule protect the digestive enzymes in the pills until they reach the duodenum.

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Question:
4(c)(i) Describe how T cells recognise and respond to the swine influenza virus.    (2 marks)

Classmate's answer:
When T cells are stimulated by antigen-bearing cells, they produce killer T cells to kill the virus directly, also helper T cells to facilitate the function of B cells.

Wrong concepts:
T cells recognise the virus by the antigen on the surface of the virus

Suggested answer:
T cells recognise the virus by the antigen on the surface of the virus. It produces killer T cells to kill the virus as well as helper T cells and memory T cells.

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Question 8a
Deduce and explain the genotype of individual 2.

Classmate answer
the offsprings of individual 2 and 1 has colour blindness, this means that at least one of their parents poses the Xb (colour blindness) allele which is recessive and only presence in homologous condition. And since individual 1 is colour blindness, he must posses Xb allele, individual 2 has to posses Xb allele in order to give birth to a colour blindness offspring. So, individual 2 genotypes is XBxb.

Wrong Concept
1. Should specify the colour blindness individual
2. Should talk about the sex-linked traits
3. Logic is weak

Suggested Changes
Being a sex-linked trait, allele for colour blindness and normal vision is on X-Chromosome. X-chromosome of individual 5 comes from individual 1 and 2. As individual 1 is colour blindness, he carries allele for colour blindness. As individual 5 is colour blindness. She carries both allele of colour blindness. One of the allele comes from individual 1 and anothe comes from individual 2. Therefore, individual 2 contain one allele for colour blindness and one for normal vision as she is with normal vision. Therefore, she is heterozygous.

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Question: 1a
According to the photomicrograph as shown above, identify cell type W. Explain how you arrive your answer.

Classmate answer:
phloem cell, as in the stem, phloem cell has a larger size than xylem cell.

Wrong concept:
Xylem cell has a larger size than phloem cell.

Suggested answer:
Xylem. The diameter of cell type W is larger than that of the sieve tubes.

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Question: 5di
Which of the above treatments support the alternative hypothesis?

Classmates answer:
Treatment E and F. Both are under the presence of light, but E has a barrier between shaded and non-shaded side to show that the shaded side has a higher concentration of auxins than the non-shaded side.

Wrong treatment identification. The fact that both are under the presence of light and the fact that there is a barrier between shaded side and nonshaded side don't support the hypothesis.

Suggested answer:
Treatment E. The shaded side of the shoot tip has much higher concentration of auxin than that of the lighted side.

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Questions:
3(b) Describe how the foetus obtains nutrients for growth.

Classmates' answer:

The foetus' belly button is connected by the umbilical cord which supply nutrients and oxygen though the arteriolar. The mentation blood and the foetus blood are separated to ensure the transporting in nutrient and oxygen, removing of waste like urea and carbon dioxide.

Wrong concepts:

1. Exchange of materials through placenta instead of umbilical cord

2. Missing point about diffusion from maternal blood into foetal blood.

3. Separation of maternal and foetal blood is irrelevant to the question and does not ensure the exchange of substances

Suggested changes:

The foetus obtains nutrients through the placenta on the wall of uterus of mother. Nutrients are passed from the mother to the foetus through the umbilical vein. The nutrients like glucose diffuses through the capillaries of placenta to reach the foetus blood