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Biology Unit 5 Chapter 16 - DNA Technology Exam Questions with Correct Answers
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Biology Unit 5 Chapter 16 - DNA Technology Exam Questions with Correct Answers
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Biology Unit 5 Chapter 16 - DNATechnology Exam Questions with
Correct Answers
(Refer to exam q) Gene therapy is used to treat the genetic disorder, ADA deficiency.
Affected individuals are unable to produce the enzyme adenosine deaminase (ADA).
Without this enzyme, T lymphocytes, a type of white blood cell, cannot provide immunity
to infection. The diagram shows the processes involved in the treatment of ADA
deficiency by gene therapy.
What is meant by gene therapy? (1) - Answer-Replacement of defective gene
The ADA gene is inserted into a virus. Give two advantages of using a virus in gene
therapy. (2) - Answer-Can inject DNA into cells;
Targets specific cells
Individuals who have been treated by this method of gene therapy do not pass on the
ADA gene to their children. Explain why. (1) - Answer-Gamete cells do not contain ADA
gene
T lymphocytes are produced in bone marrow. A bone marrow transplant from a
genetically matched donor can provide a permanent cure for ADA deficiency.
Suggest why bone marrow for a transplant is obtained from a genetically matched
donor. (1) - Answer-To prevent immune response
Explain why treatment of ADA deficiency by gene therapy must be repeated at regular
intervals, whereas a single bone marrow transplant can provide a permanent cure. (2) -
Answer-T lymphocytes have a limited life span;
bone marrow provides continual supply of T lymphocytes
(Refer to exam q) The polymerase chain reaction is a process which can be carried out
in a laboratory to replicate DNA. The diagram shows the main stages involved in the
polymerase chain reaction.
Explain why DNA is heated to 95 °C. (1) - Answer-To separate the two strands
What is the role of a primer in this process? (1) - Answer-Enables sequencing to start
What is the role of DNA polymerase? (1) - Answer-Joins DNA nucleotides
How many DNA molecules will have been produced from one molecule of DNA after 6
complete cycles? (1) - Answer-64
, Suggest one use of the polymerase chain reaction. (1) - Answer-Replication of DNA
from crime scene
Give two ways in which the polymerase chain reaction differs from the process of
transcription. (2) - Answer-Transcription uses RNA polymerase;
and one template strand whereas PCR uses both strands
Research scientists can increase the nutritional value of potatoes by genetically
engineering potato plants. A gene which results in increased protein production has
been removed from cells of an amaranth plant and inserted into cells of a potato plant.
Describe how a gene could be removed from cells of an amaranth plant and inserted
into cells of a potato plant. (6) - Answer-Cut out gene using an endonuclease;
The endonuclease cuts a DNA double strand at a specific sequence of bases called a
recognition site;
Use the same enzyme to cut;
a plasmid;
The complementary bases are fixed by the enzyme DNA ligase;
The vector is then introduced to the plant cell by a harmless virus injecting the DNA
Plasmids are often used as vectors in genetic engineering. What is the role of a vector?
(1) - Answer-Transfer genes from one organism to another
Describe the role of restriction endonucleases in the formation of plasmids that contain
donor DNA. (2) - Answer-Cut open plasmid;
Cut donor DNA, to remove gene
Describe the role of DNA ligase in the production of plasmids containing donor DNA. (1)
- Answer-Backbones joined
(Refer to exam q) There are many different restriction endonucleases. Each type cuts
the DNA of a plasmid at a specific base sequence called a restriction site. The diagram
shows the position of four restriction sites, J, K, L and M, for four different enzymes on a
single plasmid. The distances between these sites is measured in kilobases of DNA.
The plasmid was cut using only two restriction endonucleases. The resulting fragments
were separated by gel electrophoresis. The positions of the fragments are
shown in the chart below.
Which of the restriction sites were cut? Explain your answer. (2) - Answer-L and M;
The length of the fragments were 64 and 36 kilobases
The polymerase chain reaction (PCR) can be used to produce large quantities of DNA.
Describe how the PCR is carried out. (6) - Answer-DNA heated to 90 - 95°C;
causing the strands to separate;
It is then cooled to 55°C which causes primers to bind;
Temperature increased to 72°C and the nucleotides attach to the strand;
by complementary base pairing;
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