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biology a level year 2 > gene technology > Flashcards

gene technology Flashcards

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1
Q

what is the genome

A

a genome is a full set of genes in each cell

a genome can be sequenced

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2
Q

what are sequencing projects

A

the sequencing projects read the genome of a variety of organisms

Determining the genome of a simple organism allows you to know the sequence of bases that codes it

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3
Q

how do we sequence complex organisms

A

in more complex organisms the presence of introns means that knowledge of the genome cant be translated into the proteome

the proteome is the full range of proteins that can be encoded by the genome

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4
Q

what is the application of sequencing projects

A

is allows genome-wide comparison between different species allowing the determination of evolutionary relationships

Therefore we can find out about a common ancestor

Genome sequencing is also beneficial to medical research as genome comparison between individuals can allow the development of PERSONALISED MEDICATION

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5
Q

What is the human genome project

A

it has determined the sequence of bases in a human genome

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6
Q

what is the application of the human genome project

A
  1. screening for abnormal/mutated sequences
  2. allowing identification of disorders before symptoms arise
  3. Pre-implantation screening which is screening embryos for lethal alleles
  4. identification of potential antigens to use in vaccines
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7
Q

what are the ethical issues concerning the human genome project

A

ethical concerns such as the misuse and discrimination of genetic information/ data

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8
Q

what are the different sequencing methods

A

sequencing methods are constantly developing and are becoming faster and more efficient to use

Sequencing has now become computerised; once the human genome took 15 years to sequence but nowadays to can take up to as little as 26 hours

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9
Q

what is recombinant DNA technology

A

it involves the transfer of fragments of DNA from one organism (or species) to another

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10
Q

why can transferred DNA fragments be translated within cells of the recipient

A

the genetic code, transcription and translation machinery are universal, so transferred DNA fragments can be translated within cells of the recipient organisms

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11
Q

what does transgenic mean

A

it is the word used to refer to the recipient organisms of the foreign DNA by recombinant technology

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12
Q

what are the three different ways that DNA fragments can be formed and isolated

A
  1. reverse transcriptase
  2. restriction endonuclease
  3. gene machine
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13
Q

what is a reverse transcriptase

A

reverse transcriptase makes DNA copies from mRNA
They naturally occur in retroviruses

retroviruses are viruses that main genetic information comes from RNA not DNA

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14
Q

how does reverse transcriptase make DNA fragments

A
  1. the cell that produces the proteins that scientists want is chosen and should have a large amount of mRNA for the protein
  2. Reverse transcriptase can align and join the complementary DNA bases to the mRNA bases
  3. this single-stranded DNA is called complementary DNA (cDNA)
  4. you need to make the DNA double-stranded and this is done by DNA polymerase
  5. the cDNA does not have introns
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15
Q

what is a restrictive endonuclease

A

restrictive endonucleases are enzymes that “cut” DNA at restriction sites to form DNA fragments

as it is an enzyme, the restrictive endonucleases are complementary to specific restriction sites

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16
Q

how do restrictive endonucleases work

A

some cut through the same location in the double-stranded DNA to produce a blunt end

this means that no bases are exposed or overhang

some creates a staggered ends with exposed bases
These are palindromic and are called “sticky ends” because they can join to complementary DNA bases pairs

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17
Q

what does palindromic mean

A

the same but backwards

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18
Q

what is the gene machine

A

it is a computerised way to create DNA fragments which is faster and more efficient

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19
Q

how does the gene machine work

A
  1. scientists identify the amino acid sequence of the protein of interest
    They then deduce the mRNA sequence from that and the DNA sequence from the mRNA sequence
  2. The DNA sequence is entered into a computer, whciuh has to pass biosafety and biosecurity checks
  3. the computer creates small sections of overlapping DNA strands called olinguncleotides
  4. the oligonucleotides can then join to form the DNA sequence of the entire gene
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20
Q

why must we amplify the DNA fragments produced

A

to use in experiments, these DNA fragments have to be amplified - lots of them have to be made

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21
Q

what are the different ways in which a DNA fragment can be amplified

A

in vitro cloning: PCR (polymerase chain reactions)

in vivo cloning

22
Q

how does In vitro: PCR cloning work

A
  1. DNA fragments are heated to 95C so hydrogen bonds between base pairs break, producing 2 single DNA strands
  2. the mixture is then cooled to 55C to allow primers to anneal to the DNA fragments by complementary base pairings
  3. the mixture is heated to 72C as this is the optimum temperature for DNA polymerase. DNA polymerase attaches nucleotides together to form new double-stranded DNA fragments
23
Q

what are primers

A

primers are short sequences of DNA that allows the attachment of DNA polymerase

24
Q

what does the mixture in In vitro: PCR contain

A

the mixture in this reaction contains:
-DNA fragments

  • DNA polymerase (and helicase)
  • primers
  • magnesium ions (that act as a co-factor for DNA polymerase)
25
Q

how does In vivo transformation work

A
  1. DNA is cut using restriction endonuclease to create fragments with sticky ended
  2. A protomer and terminator region are added to allow transcription
  3. the same restriction endonuclease is used to cut open the plasmid ( which is a DNA loop in bacteria that acts as a vector). This means that the sticky ends of the plasmid DNA is complementary to the sticky ends containing the gene
  4. the enzyme DNA ligase is used to incorporate the DNA fragments into the plasmid - the recombinant DNA is formed
  5. the recombinant plasmid is then transferred into bacteria via heat shock or Ca2+ to increase membrane permeability
26
Q

what are a protomer and terminator

A

a protomer marks the beginning of the target gene

a terminator marks the end of a target gene

27
Q

what is a vector

A

a vector is something used to transfer DNA into cells

28
Q

why are bacteria used in In vivo cloning

A

bacteria do not contain introns

29
Q

why are marker genes important

A

not all plasmids will take up the foreign DNA fragments and not all recombinant plasmid will be taken up by the bacteria cells

therefore we need to identify which bacterial cells have taken up the recombinant plasmids.
We can do this through marker genes

30
Q

what are maker gens

A

these are used to see if plasmids were taken up by the bacteria

31
Q

how can we find out if recombinant plasmids were taken up by the bacteria

A

plasmids contain antibiotic resistance genes

we grow bacteria in agar plates containing antibiotics e.g. ampicillin
If the bacteria have taken up the plasmid, they will survive as they will contain antibiotic resistance genes

32
Q

how do we find out if the plasmids are recombinant

A
  1. A DNA fragment is inserted in the middle of a marker gene e.g. GFP, which encodes for fluorescence
  2. GFP will no longer be made, so the plasmids that do not fluoresce are recombinant and those that do are non-recombinant- they have not taken up the foreign DNA fragments
  3. this can be done in antibiotic-resistant genes too, recombinant plasmids won’t survive on your plates with antibiotic
33
Q

what is gene therapy

A

gene therapy is the mechanism by which genetic disorders can be cured or treated by masking the effect of the faulty allele with the insertion of the functional allele

34
Q

how does gene therapy work

A
  1. the healthy alleles are isolated into cells using vectors
  2. if a mutant allele is recessive, a dominant allele is inserted and if the mutant allele is dominant, DNA is inserted into the middle of it to silence it
35
Q

what are the two main types of gene therapy

A

somatic

germline

36
Q

what is somatic gene therapy

A

this is when alleles in body cells are altered (in being that has already matured), therefore changes are not passed on to the offspring

37
Q

what is germline gene therapy

A

alleles in sex cells are altered and are passed on to offspring but are considered unethical due to the concern over designer babies or the safety of gene therapy

38
Q

what are DNA probes

A

DNA probes are short sections of DNA that are complementary to a known DNA sequence e.g. a mutated allele

They are usually labelled with a fluorescent or radioactive tay

39
Q

what are DNA probes used for

A

they are mainly used for genetic screening: which is the study of an individual’s DNA to identify whether they possessed a mutated allele that causes a particular disease

40
Q

how do DNA probes work

A
  1. the labelled DNA probe is mixed with denatured DNA samples from the individual
  2. if the individual has the mutant allele, the probe will bind to the complementary base sequence in one of the DNA strands - this process is called hybridisation
  3. this hybridised DNA ( it is the combination of the mutant allele and the probe) us detected using radiation and fluroecence
41
Q

why is the DNA denatured

A

it is important that the DNA is denatured so it does not replicate

42
Q

what is DNA hybridisation

A

this is when DNA sequences of different species or individuals have complementary base pairs are mixed and therefore hybridize

the more closely related the species are, the higher temp it takes the hydrogen bonds between the two strands.

43
Q

what are the uses of DNA probes

A
  • genetic screening to see if an individual is a carrier
    of a recessive mutation or to evaluate the risk of developing diseases e.g. cancer ( if the disease was dominant, the characteristic would be displayed in the phenotype)

-allows for personalised medicine

44
Q

what is genetic counselling

A

individuals may have genetic counselling after the screening, which provides info and support about the results of the screening and how you can lower your risk of getting a particular disease

45
Q

what is genetic fingerprinting

A

it is the method used to provide a specific pattern of DNA bands from an individual’s genome

we can look at how closely related individuals are and compare DNA obtained from a crime scene with a suspect

46
Q

what are VNTRS

A

genetic fingerprinting uses pieces of DNA called VNTRS (variable number tandem repeats)

they are short sequences of DNA that have repeated themselves in variable numbers in non-coding regions

47
Q

why are VNTRS useful in genetic fingerprinting

A

in every individual they vary in length and the number of repeats, so the probability of 2 individuals having the same VNTRS is very low

this is why they are very useful in genetic fingerprinting

48
Q

how does gentic fingerprinting work

A
  1. extraction of the DNA of interest and amplication by PCR
  2. we need to digest the DNA so we can get the VNTRS that we want. We can do this using specific endonucleases to get the DNA fragments ( the VNTRs)
  3. The DNA fragments are separated by gel electrophoresis
  4. The DNA fragment is inserted at the top of the plate in gel electrophoresis. An eclectic current is switched on and the DNA fragments move towards the positive electrode.
    This is because DNA fragments are negatively charged (due to the phosphate groups)
  5. the VNTRs are hybridised at specific complementary bases by DNA probes
  6. the gel is then developed. This means that patterned bands can be visualised by placing the gel on an X-ray film as the probes can emit radiation - this is because the probes often contain radioactive tags
  7. this reveals the positions of the bands
49
Q

why do bands move down the electrophoresis gel

A

the smaller fragments move further down the gel but the larger fragments will be found near the top

The different sized fragments are separated into bands (if a band is, therefore, thicker, there is a higher amount of DNA of that specific size)

50
Q

what is DNA profiling

A

we can determine genetic relationships by looking ay how similar the bonding patterns are

51
Q

what are the uses of DNA profiling

A
  1. Forensics
  2. Medical diagnosis
  3. plant and animal breeding

biology a level year 2 (14 decks)

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