gene technology

Question 1

suggest how viruses are able to change from just infecting one species to infecting multiple

Answer 1

1. Mutation occurred in viral RNA
2. Altered tertiary structure of viral attachment protein

Question 2

Determining the genome of the viruses could allow scientists to develop a vaccine. Explain how

Answer 2

1. Could identify proteome
2. Identify antigen of pathogen

Question 3

Describe how radioactively labelled DNA probes can show that an organism contains a specific gene

Answer 3

1. Extract DNA and cut using restriction endonuclease
2. Separate fragments using electrophoresis
3. Treat DNA to form single strands
4. Identify using radiography

Question 4

What is a DNA probe?

Answer 4

1. Short single stranded DNA (not a single strand)
2. Bases complementary with DNA

Question 5

Describe how DNA is broken down into smaller fragments

Answer 5

1. Restriction endonucleases
2. Cut DNA at recognition site

Question 6

What is meant by a non coding base sequence

Answer 6

1. Does not code for amino acid

Question 7

Suggest and explain why it is important to be able to identify a specific strand of a pathogen that has spread

Answer 7

1. To see if the strain is resistant to any antibiotics
2. So can prescribe effective antibiotic

Question 8

Scientists can use proteins structure to investigate the evolutionary relationships between different species. Explain why

Answer 8

1. The closer the base sequence of amino acids are the more closely related they are
2. Protein structure related to base sequence

Question 9

Comparing the base sequence of genes provides more evolutionary information than comparing the structure of proteins. Explain why

Answer 9

1. Different base triplets code for the same amino acid
2. As genetic code is degenerate

Question 10

What features of cut plasmids and lengths of foreign DNA allow them to join

Answer 10

1. Sticky ends
2. Complementary to each other

Question 11

In a particular PCR, two different primers are added to the DNA, suggest why two different primers are required

Answer 11

1. The sequence at the ends of the target sequence are different

Question 12

Explain the role of DNA polymerase in reverse transcriptase PCR

Answer 12

1. Joins nucleotides to produce complementary strands of DNA

Question 13

Suggest one reason why DNA replication stops in the polymerase chain reaction

Answer 13

1. Limited number of primers

Question 14

Why are a variety of primers produced when detecting presence of different RNA viruses in pateints

Answer 14

1. Base sequence differs
2. Different complementary primers are required

Question 15

Biologists often use plasmids which contain antibiotic resistance genes, explain why

Answer 15

1. Act as marker genes
2. Allow detection of cells containing plasmid

Question 16

Explain how a resistant parasite population can arise

Answer 16

1. Mutation is parasite population produces resistant variety
2. Resistant survives and non-resistant dies
3. Resistant reproduces and passes on resistant allele

Question 17

Use your knowledge of enzymes to explain why restriction enzymes only cut DNA at specific restriction sites

Answer 17

1. Different length of DNA have different base sequences
2. Different shape
3. Only specififc sequence fits into active site of enzyme

Question 18

What is the role of a vector?

Answer 18

Transfer genes from one organism to another

Question 19

PCR can be used to produce large quantities of DNA. Describe how PCR is carried out

Answer 19

heated to 95 degrees celsius to break hydrogen bonds, separating strands
2. Cooled to 55 degrees
3. Primers bind and nucleotides attach by complementary base pairing
4. Temperature is increased to 72 degrees to provide optimum temperature for DNA polymerase to join nucleotides together
5. Cycle repeats

Question 20

Explain the advantage of injecting a toxin producing gene into isolated cells from a crop plant rather than directly into cells within a whole plant

Answer 20

1. Isolated cells divide by mitosis
2. Rapid production of toxin producing plants
3. All cells will produce toxin

Question 21

Describe how a gene can be removed from bacterial DNA

Answer 21

1. Restriction endonuclease
2. Cut at specific restriction points

Question 22

Explain how a gene probe can identify presence of a certain allele

Answer 22

1. Probe will bind to complementary base sequence of one of the strands in DNA hybridisation
2. As a result of complementary base pairing
3. Can be identified with autoradiography

Question 23

What is the role of a primer in PCR?

Answer 23

1. Allows replication to start

Question 24

What is the role of DNA polymerase in PCR?

Answer 24

1. Synthesise DNA by joining DNA nucleotides

Question 25

Suggest two uses of PCR

Answer 25

1. Replication of DNA from a crime scene 2. Gene cloning

Question 26

Suggest one explanation for a graph showing PCR replication levelling out

Answer 26

1. Nucleotides used up 2. Nothing to make complementary chains

Question 27

Explain how plasmids containing bacteria from another organism are made by genetic engineering and how the use of markers enables bacteria containing these plasmids to be detected

Answer 27

1. Use restriction endonucleases to cut out the desired gene from DNA to produce sticky ends 2. Use same restriction endonucleases to cut vector 3. Use DNA ligase to join the DNA and the plasmid 4. Add a marker gene 5. Add plasmid to bacteria to grow colonies then replica plate onto medium where the marker gene is expressed 6. Bacteria not killed have antibiotic resistance and the wanted gene

Question 28

Scientists made large quantities of human insulin by isolating mRNA from pancreas cells from which they produced DNA. Suggest two reasons why it was better to start with mRNA from pancreas cells rather than with the DNA

Answer 28

1. mRNA doesn’t contain introns so doesn’t need splicing whereas DNA does 2. amount of mRNA is bigger than the amount of DNA

Question 29

how are sticky ends useful in genetic engineering

Answer 29

1. joins two pieces of DNA 2. by complementary base pairing

Question 30

what is a DNA probe?

Answer 30

1. Short single stranded DNA 2. Complementary bsase sequence to target DNA 3. Attached with a radioactive label

Question 31

Scientists wanted to know which chromosomes the gene with a a specific allele was located. They obtained cells in mitosis and added a labelled DNA probe for the specific allele. Explain why they used cells in mitosis

Answer 31

1. Chromosomes are visible 2. Can see which chromosome DNA probe attached too

Question 32

To make a DNA probe a scientist had to find the base sequence of the normal gene, Once he had copies of this gene, what methods could he use to find the base sequence of the gene?

Answer 32

1. Restriction mapping 2. DNA base sequencing of fragments

Question 33

Suggest one reason why very few live birth of animals that have embryos from other species implanted

Answer 33

1. Embryo is foreign 2. So rejected/ attacked by immune system

Question 34

Explain why base pairs are a suitable way of measuring the length of a pieve of DNA

Answer 34

1. DNA made of base pairs 2. Each base pair is same length

Question 35

Explain why PCR is used when carrying out genetic fingerprinting of small amounts of ancient DNA

Answer 35

1. Only very small amount available so PCR increase amount 2. So enough available for use in genetic fingerprinting

Question 36

What are DNA primers?

Answer 36

1. Short lengths of DNA complementary to target DNA

Question 37

What is the advantage of the enzyme used in PCR being thermostable?

Answer 37

1. Doesn’t denature at high temperatures 2. So can withstand the high temp of 95 degrees

Question 38

Suggest how you could determine the size of different DNA fragments

Answer 38

1. Run DNA fragments of known lengths 2. Compare position with unknown fragments

Question 39

Explain how comparison of mitochondrial genes could indicate that there is a distinct group in a species and explain how new techniques enable the comparison of genes to be completed rapidly

Answer 39

1. Compare DNA base sequence 2. A distinct group will have different DNA from other groups 3. DNA sequencing is automated/computerised