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AQA A Level Biology > Gene Technology > Flashcards

Gene Technology Flashcards

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1
Q

What are the three ways to isolate a target gene?

A

1 - Restriction enzymes2 - Reverse transcriptase3 - Artificially synthesise a gene

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2
Q

How can restriction enzymes be used to isolate target genes?

A
  • DNA contains palindromic sites- Restriction enzymes cut palindromic at specific recognition sites- If there is a recognition site either side of a target gene, restriction enzymes can be used to cut it out - Using a restriction enzyme will leave DNA with sticky ends (unpaired bases)
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3
Q

How can reverse transcriptase be used to isolate target genes?

A
  • Cells only have two copies of each gene in their nucleus (hard to access)- Use an enzyme that reverses transcription- Form cDNA (complimentary DNA) outside of the nucleus
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4
Q

How can you artificially synthesise a gene?

A
  • Use a gene machine to make DNA from scratch- Join around 25 nucleotides together at once- Forms an oligonucleotide- Oligonucleotides can be joined together to form a synthetic gene- Allows you to design your own genes/proteins
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5
Q

What are the three steps in inserting a target gene?

A

1 - Isolate the target gene2 - Insert the gene into a vector3 - Insert the vector into a bacteria

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6
Q

What is a vector?

A

Something that is used to move DNA from one place to another

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7
Q

What are 2 examples of vectors?

A
  • Virus- Plasmid
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8
Q

How do you insert a gene into a vector?

A
  • Cut the vector with the same restriction enzyme used to isolate the target gene so that the sticky ends are complimentary- DNA ligase will then form the phosphodiester bonds between the isolated gene and the vector- Recombinant DNA is formed
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9
Q

What is recombinant DNA?

A

DNA from more than one source/organism

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10
Q

How do you insert a vector into a bacteria?

A
  • Increase the permeability of the bacterial cell wall by treating with calcium chloride and then heat shock it- Marker genes can then identify which bacteria became transgenic
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11
Q

What is a transgenic bacteria?

A

Bacteria containing recombinant DNA

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12
Q

What are marker genes?

A

Genes that are paired with target genes to check if the vector has been inserted properly

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13
Q

Why are marker genes used?

A

Vectors are often not taken up by bacteria so marker genes are used to identify which bacteria are transgenic so that we can select and culture them

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14
Q

Why are marker genes easily identified?

A

Can be antibiotic resistance, UV or radioactivity which are easily identifiable and distinguishable

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15
Q

What will transgenic bacteria contain?

A
  • Marker gene- Target gene
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16
Q

What is the PCR?

A

In vitro DNA amplification

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17
Q

What is the PCR used for?

A

Used to amplify DNA

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18
Q

What are the ‘ingredients’ needed for the PCR?

A
  • DNA sample- Free DNA nucleotides- Primers- DNA Polymerase
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19
Q

What are primers?

A
  • Short sequences of DNA complimentary to the start of the DNA sample, they anneal to a short sequence of single stranded DNA to make it double stranded so DNA polymerase can attach- They select the section of DNA to be copied
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20
Q

What is the PCR method?

A

1 - Heat to 952 - Cool to 503 - Heat to 704 - Repeat

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21
Q

In PCR why do we initially heat the sample to 95?

A

To break the hydrogen bonds between DNA nucleotides and therefore separate DNA strands

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22
Q

In PCR why do we secondly cool to 50?

A
  • Allows primers to anneal- DNA polymerase can then attach- Complimentary base pairing of primers can then give a short double stranded section of DNA
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23
Q

In PCR why do we finally heat up to 70?

A
  • DNA polymerase adds complimentary free nucleotides- Form phosphodiester bonds
24
Q

What are the six steps to obtaining many copies of a target gene which has been translated to proteins?

A

1 - Isolate the target gene using restriction enzymes 2 - Insert the gene into an appropriate vector (same restriction enzyme because of complimentary sticky ends)3 - Insert vector into bacteria to form a transgenic organism (force membrane permeability by ice cold calcium chloride and then heat shock)4 - Identify which organisms are transgenic ( marker genes)5 - Culture the transgenic organisms ( transcribe and translate recombinant DNA to make protein of the target gene)6 - Extract/purify the protein

25
Q

What is gene therapy?

A

Changing the faulty alleles that cause genetic disorders

26
Q

How is gene therapy carried out on a genetic disease which is dominant?

A
  • Sufferer heterozygous- 1 functional allele- Silence dominant allele- Use a vector to add a DNA fragment into the dominant allele- Dominant allele not transcribed- Recessive allele transcribed and translated
27
Q

How is gene therapy carried out on a genetic disease which is recessive?

A
  • Sufferer homozygous- Add functional allele to the DNA using a vector- New dominant allele is expressed
28
Q

What are the two types of gene therapy?

A
  • Germ line- Somatic
29
Q

What is germ line gene therapy?

A
  • Changing the alleles of gametes- All future off-spring inherit- Illegal in humans
30
Q

What is somatic gene therapy?

A
  • Changing the alleles of body cells (not gametes)- Off-spring will not inherit- Not permanent- Legal
31
Q

What are the possible problems that can arise from gene therapy?

A
  • Alleles inserted into wrong locus- Can silence wrong gene by mistake (e.g. tumour suppressor which will lead to cancer)- Gene over expressed- Cosmetic uses
32
Q

What are two examples of transgenic organisms in agriculture

A

Soya beans- express protein from bacteria- protein toxic to pests- fewer insects on plantGolden rice- gene from corn put into rice- express vitamin A

33
Q

What are the advantages of genetically modified soya beans?

A
  • Less chemical pesticide- More efficient food chain
34
Q

What are the advantages of genetically modified golden rice?

A
  • Prevents blindness caused by vitamin A deficiency
35
Q

What are the disadvantages of using transgenic organisms in agriculture?

A
  • Monoculture of crop with low genetic diversity- Susceptible to environmental factors- Decrease in biodiversity
36
Q

What are 2 examples of using transgenic organisms in industry and research?

A

Making enzymes- e.g. renin/lipasesTransformed pathogens to treat disease- attack other pathogens but dont affect humans

37
Q

What are the advantages of transforming pathogens to treat disease?

A
  • Treat disease- Pathogens can’t develop resistance- Reduce suffering
38
Q

What are the disadvantages of transforming pathogens to treat disease?

A
  • Mutate and infect humans- Bioweapons
39
Q

What are the advantages of making enzymes transgenically?

A
  • Cheap and easy- Reduce energy and cost
40
Q

What are 2 examples of using transgenic organisms in medicine?

A
  • Transform bacteria to express proteins- Mammals transformed to produce useful products in milk
41
Q

What are the advantages of transforming bacteria to express proteins and using mammals transformed to produce useful products in milk?

A
  • Human proteins - Cheaper and easier than making them synthetically
42
Q

What are the disadvantages of transforming bacteria to express proteins and using mammals transformed to produce useful products in milk?

A
  • Unexpected problems (e.g. cancer)- Using animals as a commodity
43
Q

What is a DNA probe?

A

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

44
Q

What are DNA probes used for?

A

To test if a sample of DNA contains a specific sequence

45
Q

How do DNA probes work?

A
  • Attach label to DNA probe- If sequence is present (e.g. disease causing allele) DNA probe will hybridise and stick to the DNA sample with the complimentary sequence- Rinse the sample to remove unhybridised DNA probes- View the labels
46
Q

What labels can be used in DNA probes?

A
  • UV- Radioactivity
47
Q

How must DNA be initially for a DNA probe to be able to hybridise?

A

Single stranded

48
Q

How does a DNA microarray work?

A
  • Label attached to human DNA not probe- Many DNA probes attached to a tile in fixed known positions- DNA will hybridise to complimentary sequence- Rinse to remove unhybridised- View labels
49
Q

What is genetic counselling used for?

A
  • Identifying carriers of specific alleles and the most efficient treatment for an individual- Healthcare professionals can advise about risks about passing on heritable diseases- Make informed decisions about treatment and prevention
50
Q

What is genetic screening used for?

A
  • Parents can find out if they are carriers of recessive alleles- Can diagnose + treat before symptoms show
51
Q

How can personalised medication be used?

A
  • Doctors can describe based of patients genotype- Change drugs if you know patient has an allele that causes a side affect with a different drug
52
Q

What is genetic fingerprinting?

A

Identifying individuals by comparing variable number tandem repeats

53
Q

What are VNTR’s?

A
  • Non-coding DNA contains lots of VNTR’s- Don’t code for proteins- Dont affect phenotype- Vary more than coding DNA- The number of repeats of each VNTR varies
54
Q

What are the 3 ways of using VNTR’s?

A
  • Relatedness- Medicine- Forensics
55
Q

How can VNTR’s be used for relatedness?

A
  • The more closely related 2 individuals the higher percent of VNTR’s match- Paternity = 50% match- used for endangered specie to make sure the two least related beed to maintain genetic diversity
56
Q

How can VNTR’s be used for forensics?

A
  • Samples from a crime scene and suspects are collected- Amplified using PCR- Run gel electrophoresis- Chance of two individuals having the same number of VNTR’s is low
57
Q

How can VNTR’s be used in medicine?

A
  • Test for specific combinations of alleles- Used to diagnose genetic disorders

AQA A Level Biology (13 decks)

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