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5C Genetic Modification
Time: 34 minutes
Total marks available: 34
Total marks achieved: ______
Andy Todd
Q1.
The picture shows a sheep that has been genetically modified to contain a human gene
for making a human protein in its milk.
The protein in its milk is a blood clotting substance called factor IX.
(a) The process of genetic modification used to produce this sheep involves the use
of two types of enzyme. One enzyme cuts DNA and the other enzyme joins DNA.
The process also used a vector.
(i) Name the enzyme that cuts DNA.
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(ii) Name the enzyme that joins DNA.
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(iii) Name a vector.
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(b) This sheep is transgenic.
What is meant by the term transgenic?
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(c) The transgenic sheep can be reproduced by cloning.
Andy Todd
Suggest the advantages of reproducing the transgenic sheep by cloning.
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(d) (i) Name the small structures in normal plasma that are involved in blood clotting.
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(ii) Explain why is it important to have blood that clots.
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(Total for question = 10 marks)
Andy Todd
Q2.
(a) Describe the stages that are used to genetically modify a bacterium that is able to
manufacture human growth hormone.
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(b) BST is a hormone that increases milk yield in cows.
(i) Explain what is meant by the term hormone.
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(ii) In some countries BST from genetically modified bacteria has been injected
into cows to improve milk production.
In other countries selective breeding has been used to improve milk production.
Describe how selective breeding could be used to increase milk production.
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(Total for question = 10 marks)
Andy Todd
Q3.
Describe the stages by which a bacterium can be genetically modified to produce
large amounts of a named human protein.
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(Total for question = 5 marks)
Andy Todd
Q4.
(a) Describe how micropropagation (tissue culture) can be used to produce large
quantities of identical plants.
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(b) Explain what is meant by the term genetic modification (GM) and suggest why a
farmer might want to grow a GM crop.
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(Total for question = 9 marks)
Q1.
This question examined knowledge and understanding of genetic modification and
cloning. Many candidates were able to recall the names of the enzymes involved in
parts (a) (i) and (ii), though the examiners noted that the spelling of restriction
and ligase was often incorrect. Candidates were still credited but are encouraged
to try to spell biological terms correctly. Less than half the candidates were able to
recall the name of a vector in part (iii) as a plasmid or a virus. Those who wrote
'bacteria' alone were given no credit. In part (b), the examiners only gave credit
for answers that showed that the gene being transferred came from a different
species, not animal or organism. Part (c) posed problems for many candidates.
Many failed to produce answers that discussed the transgenic sheep in the
question. Listing the sequence of events involved in cloning failed to gain credit as
Andy Todd
did general responses discussing the benefits of transgenic techniques or cloning.
The examiners rewarded candidates who understood that the advantages of
reproducing the transgenic sheep by cloning are that there would be lots of
genetically identical sheep producing lots of the factor IX and that there would be
no need to repeat the GM procedure. In part (d), most appreciated the role of
platelets in blood clotting and that loss of blood is prevented, as is entry of
pathogens.
Q2.
In part (a) students did less well with a few seeming to have no idea about genetic modification.
The better responses included extraction of the gene, that codes for growth hormone, from
human DNA using a restriction enzyme. Using the same restriction enzyme to cut a bacterial
plasmid and using ligase to insert the human gene into the plasmid to make a vector contain
recombinant DNA. In part (b)(i) students had to explain what is meant by a hormone. The
majority of students earned some credit. The best responses clearly stated that a hormone is
released by endocrine glands into the blood stream carried to target cells upon which it has an
effect. In part (ii) students had to describe how selective breeding could be used to increase milk
production. About half of the answers scored full marks. Some responses had cows mating with
other cows, some referred to cloning and some had cows marrying! The best responses
described selecting cows with high milk yield and mating these with bulls from mothers who had
high milk yield. This process could then be repeated with their offspring for many generations.
Q3.
There were many outstanding answers to this question, often showing impressive use of correct
terminology. There were, however, some who failed to score much credit by simply giving vague
references to DNA cutting or irrelevant discussions about fermenters. Sadly, very few actually
named a human protein in their answer. Those who did often chose insulin.
Q4.
There were many excellent answers to part (a) by students who knew all the
salient facts about tissue culture, notably the use of explants to culture on
nutrient agar under sterile conditions, combined with the further use of plant
growth regulators and the provision of sensible abiotic factors. Weaker
candidates merely repeated the stem of the question and gained little credit
with the rest of their answer. Most often they would confuse tissue culture with
some other biological process, often selective breeding. Part (b) was more
accessible with most appreciating that the process of genetic modification
involved the transfer of genes using enzymes and vectors to produce plants
with desirable qualities, most often named as high yielding or pest resistant.
Again, weaker candidates wrote about selective breeding and lost credit as a
result. They also rephrased the stem of the question and stated that the term
genetic modification means that genes are modified. Candidates need to be
more aware that rephrasing the stem of a question will not gain credit.
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Q1.
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Q2.
Q3.
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Q4.
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