Gene Technologies

Question 1

Why is DNA considered a universal code?

Answer 1

Every organism uses the same 4 bases; A, T, C, G

Question 2

What are DNA fragments?

Answer 2

Sections of DNA that are transferred

Question 3

3 different ways DNA fragments can be made

Answer 3

• Reverse transcriptase
• Gene Machine
• Restriction endonuclease

Question 4

What is reverse transcriptase and how is it used?

Answer 4

• An enzyme that converts single stranded mRNA to double stranded DNA
• The DNA it produces is called cDNA(complementary DNA)

Question 5

How is reverse transcriptase used to make recombinant DNA?

Answer 5

• mRNA with target gene is isolated
• mRNA is mixed with reverse transcriptase
• Reverse transcriptase converts mRNA to cDNA
• cDNA can now be used to make recombinant DNA

Question 6

What are recognition sequences?

Answer 6

Sections of DNA where the base sequences has palindromic base pairs

Question 7

What do restriction endonucleases do?

Answer 7

Bind to recognition sequences

Question 8

How is a DNA fragment produced using restriction endonuclease?

Answer 8

• DNA containing the target gene is mixed with restriction endonuclease
• Restriction endonuclease binds to the recognition sequences on either side of the target gene
• So the target gene is cut out

Question 9

How to make DNA fragments using a gene machine?

Answer 9

• The target gene sequence is taken from a database
• Nucleotides are added in the correct order to synthesise the correct base sequence
• Protecting groups are added so no side branches are produced

Question 10

How are DNA fragments amplified? (In Vivo)

Answer 10

• Vector DNA is cut up by restriction endonuclease to leave sticky ends
• DNA fragments have complementary sticky ends
• Sticky ends of the DNA fragment and DNA vector bind together by DNA ligase during ligation
• Vector transports the recombinant DNA to host cell - plasmid taken up by heat shock, bacteriophage; DNA injected
• Marker genes are added alongside antibiotic resistance

Question 11

How can transformed DNA be recognised?

Answer 11

• Place them on an agar plate with antibiotics
• Cells that have recombinant DNA will survive
• So they can be grown in large numbers to amplify target gene

Question 12

How are DNA fragments amplified? (In Vitro, PCR)

Answer 12

• DNA fragments are mixed with primers, DNA polymerase and free nucleotides
• Reaction is heated to 95℃, then cooled to 65℃ so the primers can anneal to the 2 separate strands
• It is then heated to 72℃, DNA polymerase produces 2 separate and adds the complementary free nucleotides
• Process is repeated

Question 13

How does recombinant DNA improve crop yield?

Answer 13

• Increases resistance to disease
• Increases tolerance to herbicides and pesticides
• Increases tolerance to adverse environmental conditions

Question 14

How does recombinant DNA make livestock more economically viable?

Answer 14

• Makes them grow faster and larger

- Increases resistance to disease

Question 15

How is recombinant DNA used is medicine?

Answer 15

• To produce drugs and hormones

- Manufacture enzymes

Question 16

Ethical issues with recombinant DNA

Answer 16

• Modified genes can spread to other organisms where it is harmful eg, bacteria or organic crops
• Could lead to reduce diversity
• Decreased income for low income countries where these products come from
• The use of recombinant DNA could to selecting traits in embryos

Question 17

Gene therapy procedure

Answer 17

• Introduction of target gene into the genome
• The target gene is then transcribed and translated to produce desired protein
• Protein counteracts the effect of the disease

Question 18

What is somatic therapy?

Answer 18

• altering alleles in adult body cells

Question 19

What is germline therapy?

Answer 19

• altering alleles in sex cells

Question 20

What is a DNA probe?

Answer 20

• A section of single stranded DNA

- Complementary to the DNA of the target gene

Question 21

What is hybridisation?

Answer 21

• When the complementary base sequence bind to the DNA probe sequence

Question 22

How are DNA probes used in diagnoses?

Answer 22

• DNA probes are labelled with radioactive phosphate or fluorescent tag
• If the disease causing allele is hybridised, the label would be detected

Question 23

What is electrophoresis?

Answer 23

• Technique that separates DNA fragments according to size
• DNA probes that are labelled with fluorescent tags are washed over
• DNA probes hybridise with complementary fragments

Question 24

What are microarrays?

Answer 24

• Technique that use many DNA probes at once
• It has many indents which contain a DNA probe for a specific gene
• The fluorescent tagged DNA is washed over
• Complementary fragments will hybridise with DNA probe

Question 25

What can genetic screening be used for?

Answer 25

- If an individual is a carrier of a genetic disease - If an individual is at a greater risk of developing a disease - How likely an individual will respond to a specific drug

Question 26

What are VNTRs?

Answer 26

- Sections of DNA that repeats | - Variable number tandem repeats

Question 27

The function of VNTRs?

Answer 27

- To allow comparison between individuals, as it is very unlikely that individuals will have the exact same number of VNTRs in the same place

Question 28

How is DNA amplified for electropheresis?

Answer 28

- Using PCR

Question 29

How are the DNA fragments recognised?

Answer 29

- Due to the fluorescent tags

Question 30

How are the DNA fragments inserted into the well?

Answer 30

- At the negative end, in gel that conducts electricity

Question 31

What determines the lengths of the DNA fragments?

Answer 31

- The number of repeats of the VNTRs

Question 32

What can genetic fingerprints be used for?

Answer 32

- Genetic relationships - Genetic variability - Forensic science - Medical diagnosis - Inbreeding

Question 33

How can you see a fluorescent tag?

Answer 33

- Using UV light

Question 34

How can you see a radioactive tag?

Answer 34

- Using X-ray film