Aqa gce biology b june 2003 question paper

General Certificate of EducationJune 2003Advanced Subsidiary Examination BIOLOGY (SPECIFICATION B)
Unit 2 Genes and Genetic Engineering
In addition to this paper you will require:
a ruler with millimetre measurements.
• Use blue or black ink or ball-point pen.
• Fill in the boxes at the top of this page.
• Answer all questions in the spaces provided. All working must be shown.
• Do all rough work in this book. Cross through any work you do not
• The maximum mark for this paper is 54.
• Mark allocations are shown in brackets.
• Answers for Questions 1 to 7 are expected to be short and precise.
Question 8 should be answered in continuous prose. Quality of Written
Communication will be assessed in the answer. You will be awarded upto 1 mark for your ability to use an appropriate form and style of writing,to organise relevant information clearly and coherently, and to usespecialist vocabulary, where appropriate.
handwriting and the accuracy of your spelling, punctuation and grammar Copyright 2003 AQA and its licensors. All rights reserved.
Answer all questions in the spaces provided.
Describe what happens to the chromosomes during each of the following stages ofmitosis.
Complete the table to give two differences between mitosis and meiosis.
The diagram shows the replication of a molecule of DNA.
Explain why DNA replication is described as semi-conservative.
What is meant by specific base pairing? Explain why specific base pairing is important in DNA replication.
Describe two features of DNA which make it a stable molecule.
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The diagram shows one method of cloning mammals.
Explain why the new individual will be genetically identical to the adult mammal fromwhich the body cell was taken.
Suggest why a nucleus from a body cell is used instead of a nucleus from a sperm or anegg.
Give one advantage and one disadvantage of producing mammals by cloning rather than
by sexual reproduction.
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Phenylalanine is an amino acid found in many proteins in the diet. In most people it isconverted to another amino acid, tyrosine, by the pathway shown.
People with phenylketonuria cannot produce the enzyme phenylalanine hydroxylase.
This disorder is the result of a gene mutation. Affected people accumulate phenylalanine andthis leads to brain damage.
Explain how the gene mutation results in failure to produce the enzyme phenylalaninehydroxylase.
From birth, children with phenylketonuria are given a special diet which is low inphenylalanine.
Explain how such treatment prevents brain damage in the children.
Suggest one reason why the diet must contain some phenylalanine.
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In the production of genetically engineered bacteria, a human gene was first combined with a
bacterial plasmid containing two antibiotic resistance genes. One gene coded for resistance to
tetracycline and one for resistance to ampicillin. The human gene was inserted in the centre
of the gene coding for resistance to tetracycline as shown in Figure 1.
The human gene has split the gene coding for resistance to tetracycline. What effect willthis have? The plasmids were then added to a bacterial culture. Replica plating was used to find out
which bacteria had taken up the plasmid containing the gene. This is shown in Figure 2.
Explain why each of the following was used.
The agar plate containing ampicillin.
The agar plate containing tetracycline.
Draw a circle around the colony containing the human gene.
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Alpha-l-antitrypsin (αAT) is a protein needed to prevent the breakdown of the elastic tissuein the lungs. Some people have a different form of the gene for αAT. These people cannotproduce the αAT protein.
What term is used to refer to different forms of a gene? People who are unable to produce αAT can be treated with αAT extracted from the milkof genetically engineered sheep. These sheep are produced by inserting the human αATgene into the fertilised eggs of sheep. These eggs are allowed to develop into embryoswhich are then implanted into surrogate sheep.
Suggest one reason why
only a few live births result from the large number of embryos implanted; only 1 in 20 of the female sheep born produce αAT in their milk.
When sheep capable of producing αAT in their milk are allowed to breed, some of theirfemale offspring are also able to produce milk containing αAT.
Explain how the ability to produce milk containing αAT is passed from mother tooffspring.
Suggest why only some of the female offspring produce milk containing αAT.
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The diagram shows the movement of chloride ions and water in the cells of the lung of ahealthy human.
In people with cystic fibrosis the gene controlling the movement of chloride ions isdefective. Explain why the movement of chloride ions and water is reduced in a personwith cystic fibrosis.
People with cystic fibrosis produce mucus which is stickier and thicker than healthypeople. Suggest why people with cystic fibrosis are more likely to develop bacterialinfections, such as pneumonia.
Describe one way in which normal genes might be introduced into the cells lining the
airways of the lungs.
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Question 8 should be answered in continuous prose.
Quality of Written Communication will be assessed in these answers.
DNA fingerprinting can be used to identify an individual from a small spot of blood. Thediagram shows a DNA fingerprint.
After the DNA has been extracted from the blood, it is copied by the polymerase chainreaction (PCR).
The DNA is then cut into fragments, which are separated by electrophoresis. Describe the main stages in the copying, cutting and separation of theDNA.
The position of the fragments is determined by the use of radioactive probes. Theseprobes consist of short lengths of DNA with specific base sequences, which bind onto thefragments. Suggest why several different probes have to be used to produce a DNAfingerprint with a large number of bands.
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