Question: 1

Molecular evidence has shown that all specimens of the English Elm tree, Ulmus procera, form a genetically isolated clone. English Elms developed from a variety of elm brought to Britain from Rome in the first century A.D.

Although English Elm trees make pollen, they rarely produce seeds. Instead they spread by developing structures known as suckers from their roots. Each sucker can grow into a new tree.

This tendency of elms to create suckers has been exploited by humans, who have separated the suckers, with roots attached, and used them to plant hedges and establish new woodlands.

(a) (i) Suggest a technique that could be used to provide molecular evidence that all English Elm trees form a clone.

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(ii) State why the English Elm clone is genetically isolated from other varieties of elm.

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(iii) State the name given to the process in which plants reproduce asexually by means such as suckers.

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[1]

(b) In 1967, a new, virulent strain of an elm disease fungus arrived in Great Britain on imported timber. Beetles that lived under the bark of elm trees spread the fungus.

The saws used to cut down dead branches were not sterilised after use. When the saws were used to prune healthy trees, these trees became infected. Approximately 25 million elm trees, most of the English Elm population, died within a few years of the arrival of this fungus.
Explain why there was such a rapid loss of elm trees in Britain as a result of this elm disease.

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[4]

(c) Elm trees respond to fungal infection by plugging their xylem vessels. The leaves on the upper branches of the tree then turn yellow and die. When most of the branches have lost their leaves and died, the roots are weakened and may also die.

(i) Explain why the plugging of xylem vessels will result in the leaves of the upper branches turning yellow.

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[2]

(ii) Explain why the loss of leaves from the tree may result in the death of the tree’s roots.

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[2]

(d) Many ornamental plants for gardens can be cloned by tissue culture.

Describe the process of cloning plants by tissue culture.

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[7]

(e) List two advantages and two disadvantages of cloning plants by tissue culture.

advantage 1

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advantage 2

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disadvantage 1

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disadvantage 2

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[4] [Total: 22]

Question: 2

This question is about genetic engineering and the techniques used for making multiple copies of genes (gene cloning).

(a) Genetic engineering uses the following:

A an enzyme that synthesises new DNA

B an enzyme that cuts DNA at specific sequences

C an enzyme that reseals cut ends of DNA

D small circular pieces of DNA found in bacteria; these pieces of DNA have antibiotic resistance genes

E an enzyme found in some viruses with an RNA genome; this enzyme converts RNA into DNA.

Name A to E.

A

B

C

D

E

[5]

(b) Genes are cloned for a number of reasons. For example,

one group of research scientists at a hospital wanted to sequence a disease-causing mutation to learn more about a human disease; these scientists started their research using white blood cells;

another group of scientists at a biotechnology company wanted to clone the insulin gene in order to manufacture its protein product to treat diabetes; these scientists started their research using cells from the pancreas.

Suggest and explain the biological reasons why the two groups each started with a different cell.

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[4]

(c) A gene can be cloned in vitro (in a test-tube) by the polymerase chain reaction (PCR).

Alternatively, a gene can be cloned in vivo (in living cells) by introducing the gene into bacterial host cells.

Table 5.1 identifies some of the key steps in each process.

Compare the two processes of gene cloning by explaining the advantages of each.

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[8]

[Total: 17]

Question: 3

(a) Genetic modification of organisms uses a “toolkit” that includes:

enzymes that cut DNA

enzymes that join sections of DNA together

vectors that introduce DNA into new host cells.

Some of the enzymes and vectors that are important in genetic modification are given an identifying letter in Table 4.1.

Select one correct letter from Table 4.1 to fit each of the following statements.

An enzyme that cuts DNA

An enzyme that joins sections of DNA together

A vector to introduce foreign DNA into bacteria

A vector to introduce foreign DNA into plant cells

A vector to introduce foreign DNA into animal cells

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(b) Discuss the potential benefits to mankind and the ethical concerns raised by the following examples of genetically modified organisms:

rice modified for increased vitamin A content (‘Golden Rice™’)

humans having somatic gene therapy treatment for a genetic disease.

[9]

[Total: 14]

Question: 4

(a) The Oxford Botanic Garden was founded in 1621 to grow plants for the teaching of medicine. Since that time it has seen many changes. When the ideas of Linnaeus were adopted in the 18th century, the plants were dug up and re-planted in family groups according to his new system of taxonomy.

Recently, the plants have once again had to be re-organised:

• DNA sequencing techniques, together with cladistic analysis, have provided a radical new view of plant evolutionary relationships.

• The same techniques have also improved the ability of researchers to pinpoint new cures for diseases, by examining the closest relatives of plants already known to have medicinal properties.

(i) Comment on what the different arrangements of plants in the Oxford Botanic Garden over time tell us about the nature of scientific knowledge.

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(ii) Suggest two purposes of a plant collection in a modern botanic garden.

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(b) DNA sequencing techniques have provided new information about plant relationships.

Outline the roles of each of the following procedures in sequencing a genome:

(i) the polymerase chain reaction (PCR)

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(ii) electrophoresis

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(iii) digestion of DNA by restriction enzymes.

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(c) Suggest why a genome has to be fragmented before sequencing.

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(d) Table 5.1 lists some plants considered for genome sequencing by the ‘Floral Genome Project’. The chromosome numbers and genome sizes in mega base pairs (Mbp) are shown.

One Mbp is equal to 1 000 000 base pairs of DNA.

(i) The sequencing method that will be used is only able to sequence fragments of DNA with a maximum length of 750 base pairs.

Calculate the minimum number of DNA fragments that would need to be sequenced to read the genome of Amborella.

Show your working.

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(ii) Monkey flower and blueberry belong to the same taxonomic group within the plant kingdom. Only one of the pair was chosen for further sequencing work.

Using the data in Table 5.1, suggest reasons why monkey flower was chosen instead of blueberry.

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[2]

(iii) Use your knowledge of the effects of polyploidy in bread wheat to suggest one way in which the fruit of a hexaploid (6n) blueberry might differ in appearance from that of a diploid (2n) blueberry.

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(e) DNA sequence information is most useful when used with the phylogenetic (cladistic) approach to classification.

How does the phylogenetic approach to classifying species differ from the biological species concept?

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[2] [Total: 18]

Useful link for genome sequencing
http://genome.wellcome.ac.uk/doc_WTD021037.html

Useful videos
www.youtube.com/watch?v=ywLpxuaRWf8
www.youtube.com/watch?v=2iGtfsUt3XY