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Biology Year 2 > Chapter 21 - Recombinant DNA Technology > Flashcards

Chapter 21 - Recombinant DNA Technology Flashcards

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1
Q

What are the 3 methods of isolating target genes

A
  • Restriction enzymes
  • Reverse transcriptase
  • Artificially synthesising a gene
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2
Q

Explain how restriction enzymes can be used to isolate target genes

A
  • DNA contains palindromic sites (eg RACECAR)
  • Restriction enzymes cut DNA at specific palindromic sites called restriction sites
  • If there’s a restriction site either side of a target gene restriction enzymes can be used to cut it out
  • Using a restriction enzyme will leave sticky ends (unpaired bases)
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3
Q

Explain how reverse transcriptase can be used for isolating target genes

A
  • Reverse transcriptase is an enzyme that conducts transcription backwards
  • RNA polymerase usually used to get mRNA from DNA
  • Instead reverse transcriptase is used to get cDNA (complementary DNA) for mRNA
  • cDNA has no nucleus
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4
Q

Explain how a gene can be artificially synthesised

A
  • A gene machine is used to make DNA from scratch
  • 25 nucleotides are joined together at once
  • This forms an oligonucleotide
  • These can be joined to form a synthetic gene
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5
Q

What is meant by a vector

A

Something used to move DNA from one place to another

Eg plasmids

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6
Q

What is meant by recombinant DNA

A

DNA from more than one source/organism

eg plasmid and target gene

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7
Q

What is meant by a transgenic organism

A

An organism that contains recombinant DNA

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9
Q

Why is ice-cold calcium chloride and heat shock used

A

This increases the permeability of bacterial cell wall

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10
Q

What is a marker gene

A

A gene paired with a target gene that can be identified to check if the vector has been infected properly

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11
Q

Why do marker genes need to be used

A
  • Vectors are often not taken up by bacteria
  • Marker genes need to be used to tel which bacteria have become transgenic you need marker genes
  • Transgenic bacteria contain the recombinant DNA
  • These can be selected and cultures in transgenic bacteria
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12
Q

What marker genes are often used

A

UV fluorescence or antibiotic resistance

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13
Q

How can UV and antibiotic resistance be identified

A
  • Flourescent under UV light

- Able to survive in a culture with the antibiotic

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14
Q

What is the purpose of the polymerase chain reaction (PCR)

A

To amplify DNA (make millions of copies)

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15
Q

What is PCR sometimes called

A

in vitro DNA amplification

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16
Q

What is needed for PCR

A
  • DNA sample
  • Free DNA nucleotides
  • Primers are used to select which part of the DNA is copied
  • DNA polymerase
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17
Q

What are primers

A

Short sequences of DNA that are complementary to the start of the DNA sample

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18
Q

Describe the method of PCR and explain each stage

A 
Heat to 95
Cool to 50
Heat to 70
Repeat
In folder
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19
Q

Summarise gene technology

A
  • Isolate target gene
  • Insert gene into vector
  • Insert vector into bacteria
  • Identify transgenic organisms
  • Culture transgenic bacteria
  • Extract and purify protein
    Infolder
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20
Q

What is gene therapy

A

Changing faulty alleles that cause genetic disease

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21
Q

Explain an example of gene therapy for dominant alleles

A

Huntington’s

  • Sufferer will be heterozygous
  • They already have the functional allele
  • Have to silence dominant allele
  • Use a vector to add a DNA fragment into the dominant allele
  • Dominant allele won’t be transcribed
  • Recessive allele expressed
22
Q

Explain an example of gene therapy for recessive alleles

A

Cystic fibrosis

  • Sufferer will be homozygous
  • Use a vector to add the functional allele to DNA
  • Dominant allele will be expressed
23
Q

What are two types of gene therapy

A

Germ line gene therapy

Somatic gene therapy

24
Q

What is germ line gene therapy

A

Changing the alleles of gametes

Future offspring inherit changes

25
Q

What is somatic gene therapy

A

Changing the alleles of body cells

Offspring don’t inherit changes

26
Q

What are some possible problems with gene therapy

A
  • Alleles could be inserted into the wrong locus
  • Could silence wrong gene by mistake (eg tumour suppressor gene causing cancer)
  • Gene could be overexpressed
  • Use of gene therapy could be used for non-medical purposes eg cosmetic
27
Q

What are some examples of genetically modified organisms in agriculture

A

Golden rice

soya beans

28
Q

What are the uses of golden rice

A
  • Gene from corn
  • Put in rice
  • Expresses vitamin A to reduce vitamin A deficiency which causes blindness
29
Q

What are the uses of GM soya beans

A
  • Express protein from bacteria
  • Protein is toxic to insects
  • Fewer insects eat soya plants
  • Less need for pesticides
  • More efficient food chain so less energy is wasted
30
Q

What are some disadvantages of GM crops

A
  • Create a monoculture, less diversity so susceptible to disease
  • Have to buy seeds every year as second generation are infertile
  • Decreases biodiversity
31
Q

What is an example of how GM organisms in industry and research

A
  • Making enzymes eg rennin

- Transformed pathogens to treat disease, they attack other pathogens but don’t infect humans

32
Q

What is a disadvantage of making enzymes

A

Reduces energy usage and cost

33
Q

What are advantages of using transformed pathogens to treat disease

A
  • Pathogens won’t develop resistance

- Reduces suffering from disease

34
Q

What are disadvantages of using transformed pathogens to treat disease

A
  • Could mutate and infect humans

- Could be used as a bio weapon

35
Q

What is an example of how GM organisms can be used in medicine

A

Insulin

36
Q

What are some uses of genetically modified organisms for medicine

A
  • Can transform bacteria to express proteins so make human proteins, which is cheaper and easier than synthetically making proteins
  • Mammals can be genetically modified to produce useful products in their milk
37
Q

What are some disadvantages of using GM organisms for medicine

A
  • Possible unexpected problems eg cancer

- Ethical issues such as using animals as commodities

38
Q

What is a DNA probe

A

A short sequence of DNA (with a label attached) that is complementary to a specific allele/mutation/gene

39
Q

Explain how DNA probes are used

A
  • Used to test if a sample of DNA contains a specific sequence
  • Attach a label to DNA probe
  • If sequence is present DNA will hybridise (form hydrogen bonds) and stick to DNA sample with a complementary sequence
  • Rinse to remove unhybridised DNA probes
  • View labels eg UV
  • DNA must be single stranded for this to work
40
Q

Describe DNA microarray

A
  • Label attached to human DNA
  • Test for multiple alleles/mutations at once
  • Many DNA probes attached to a tile in a grid
  • Add patients DNA with label attached
  • DNA will hybridise to complementary DNA
  • Rinse
  • View labels
43
Q

Explain how target genes can be inserted

A
  • Isolate target gene (restriction enzymes, reverse transcriptase or gene machine)
  • Add promotor region, terminator region, sticky ends and marker gene
  • Insert gene into a vector by using restriction enzymes to cut plasmid
  • Sticky ends are complementary
  • DNA ligament enzymes reform the phosphodiester bonds
  • Forming recombinant DNA
  • Insert vector into bacteria
  • Bacteria becomes a transgenic organism
  • Use ice-cold calcium chloride and heat shock
44
Q

What are some uses of DNA probes

A

Genetic counselling
Genetic screening
Personalised medicine

45
Q

How can DNA probes be used for genetic counselling

A
  • Identify carriers of genetic disease, specific allele and most effective treatment
  • Healthcare professionals can advise people about the risks eg passing on heritable diseases, developing disease later in life and making decisions of treatments and preventions
46
Q

How can DNA probes be used for genetic screening

A
  • Parents can see if they are carriers of recessive alleles (IVF)
  • Can diagnose and treat before symptoms show eg babies are screened for cystic fibrosis
47
Q

How can DNA probes be used for personalised medicine

A
  • If a doctor knows a patients genotypes, they can give them the best drugs for them
  • If you know a patient has an allele that causes a side effect with the normal drug they can be given another
48
Q

What is the purpose of genetic fingerprinting

A

Identifying individuals by comparing the differences in their variable number tandem repeats

49
Q

Explain the process of how genetic fingerprinting allow you to identify individuals

A
  • Non-coding DNA contains lots of variable number tandem repeats
  • Don’t code for proteins
  • Don’t effect phenotype
  • Vary more than coding DNA
  • The number of repeats of each VNTR varies
50
Q

How can genetic fingerprinting be used for forensic use

A
  • Samples of DNA from crime scene and suspects are needed
  • Amplify DNA using PCR
  • Run gel electrophoresis
  • The chance of 2 individuals having the same number of VNTR’s is very low
51
Q

How can genetic fingerprinting be used for relatedness

A
  • The more closely related 2 individuals are, the higher the percentage match of VNTR’s eg paternity test =50%
  • Conservation of endangered species
  • Avoid inbreeding I’m small population by mating least related individuals to maintain genetic diversity
52
Q

How can genetic fingerprinting by used for medical diagnosis

A
  • Genetic fingerprints can be used to test for specific combinations of alleles
  • So can be used to diagnose genetic disorders

Biology Year 2 (10 decks)

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