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Biology - A-level > genetic technologies > Flashcards

genetic technologies Flashcards

1
Q

what is the genome

A

all the genetic info in an organism or cell

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2
Q

how is the genome sequenced

A

cutting the DNA into fragments which are sequenced and them put back into the correct order to give the whole genome

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3
Q

what are genome projects

A

use technology to determine the complete sequence of bases that make up the DNA of an organism

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4
Q

how can sequenced genomes be used in biology

A

-compare with particular species to highlight disease risk or identify mutations which cause disease - so can gte early diagnosis and treatment
-comparision of genomes between speceis can be used to explain the evolutionary relationships between species and used to build phylogenetic trees

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5
Q

what is bioinformatics

A

science of collecting and analysing complex biological data such as genomes

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6
Q

what is the proteome

A

sequence of protiens coded for by the DNA base sequence in the genome at a given time

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7
Q

how can the proteome be determined

A

by sequeceing the genome

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8
Q

why is finding the genome of prokaryotes easier than eukaryotes

A

-only have one circular length of DNA - cDNA
-no non-coding regions

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9
Q

how has sequencing the proteome advance medicine

A

-produce vaccines faster
-monitor mutations
-nonitor variations as the pathogen evolves
-idnetify antibiotic resisitance mechanisms

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10
Q

why is eukaryote genome more difficult to sequence

A

-has introns which need to be removed
-these are non-coding - ie junk DNA or regulatory genes (switch on/off coding regions)
-make up 98.5% of DNA

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11
Q

what was the human genome project

A

In the 1980s Cambridge scientists had been working on sequencing the genome of a nematode. As they progressed they realised that the technology used in this research could be applied to the human genome
The Human Genome Project (HGP) began in 1990 as an international, collaborative research programme
It was publicly funded so that there would be no commercial interests or influence
DNA samples were taken from multiple people around the world, sequenced and used to create a reference genome
Laboratories around the globe were responsible for sequencing different sections of specific chromosomes
It was decided that the data created from the project would be made publicly available
As a result, the data can be shared rapidly between researchers
The information discovered could also be used by any researcher and so maximised for human benefit
By 2003 the human genome had been sequenced to 99.9% accuracy
The finished genome was over 3 billion base pairs long but contained only about 25,000 genes
This was much less than expected
Following the success of sequencing the human genome scientists have now moved onto sequencing the human proteome
The proteome is all of the proteins that can be produced by a cell
Although there are roughly 25,000 genes within the genome there are many more proteins within the proteome. This may is due to processes such as alternative splicing and post-translational modification
There is also work being done on the human epigenome
These are the inherited changes in DNA that do not involve a change in DNA base sequence

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12
Q

what is DNA sequencing

A

process of determining the sequence of nucleotides in a piece of DNA

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13
Q

what was Sangers technique to sequence DNA

A

-1977
-very basic - used radioactive bases as the stop base
-then X-ray and view by hand
-more complicated and time consuming

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14
Q

what is the modern process of Sanger sequenceing

A

-primer binds to the DNA
-DNA polymerase can make the new DNA by adding nucleotides to the growing chain
-this happens unitl by chance it add a coloured dideoxy nucleotide - meaning it lacks a OH
-this is labbelled as the final positon
-fragments are run through a matrix calld gel electrophoresis which sperates the fragments by size
-short fragments run quickly, long fragments more slowly
-exposed to laser allowing the colours to be detected - so allowing the last nucleotide in the chain to be detected
-from the colurs of dye emitied by the chain terminating nucleotide, the orginal sequence of DNA can build up one nucleotide at a time

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15
Q

how has DNA sequencing changed

A

-made cheaper
-more cost-effective
-large scale
-faster

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16
Q

how many bases are there in the human genome

A

3.2 billion

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17
Q

what is genetic engineering

A

process where a gene from one organism is insterted into the genome of another - so it has the desired characteristic

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18
Q

how does genetic engineering work

A

-useful gene is identified
-useful gene is cut form the DNA using enzymes
-the gene is inserted into a plasmid vector
-plasmid containing the desired gene is inserted into the bacteria so it can multiply

19
Q

give 3 examples of organisms that have been genetically modified

A

-bacteria - useful subastances such as human insulin
-food crops - improve yield,better resistance to disease/pests
eg Bt Cotton has resisatance to a specific catipillar pest
eg Golden rice - improve vitamin A - beta-carotene which is converted to vitamin A in the body
-sheep -produce useful bacteria/vitamins in thier milk

20
Q

what are the benefits of GM organisms in medicine

A

-can produce large amounts of protiens like insulin and other drugs very fast
-human insulin made this way will not be rejected by the body
-it will allow treatment for some human genetic disorders in the future

21
Q

what are the negatives of GM organisms in medicine

A

-very expensive

22
Q

what are the benefits of GM crops

A

-resistant to pests and diseases whihc allow plats to gorw better and increase the yield
-produce more food
-produce more nutritious food in places that they cant grow lots
-reduce the use of chemical pesticides

23
Q

what are the negatives of GM crops

A

-inserted genes could be transferred to wild/natural pop of plants which could affect biodiversity of the plants and insects that feed on them
-especially resistant genes could stop farmers being able to control the growth of weeds and other plants
-some people have objections as they believe it is not natural
-has the effects of eating GM crops been studied enough in humans?

24
Q

what are the 5 stages of gene cloning and transfer

A
  1. isolation- DNA fragment that has the desired gene for the desired protien
  2. insertion- DNA into a vector
  3. transformation- DNA vector into the host cell
  4. identification- id which host cells have actually taken up the gene - using gene markers
  5. cloning/growing- host cell into the product
25
Q

how can GMOs be used in making proteins

A

-will produce purer, less chance of rejections and cheaper than extraction from an animal donor
-genetic code isuniversal so the GMOs make the same protein as the original donor

26
Q

what are the 3 ways to isolate gene fragments

A
  1. using reverse transcriptases to make DNA from mRNA
  2. using restriction enzymes to cut a section of DNA from the genome
  3. using a gene machine to build a section of DNA using nucleotides
27
Q

how does using reverse transcriptase to make mRNA/cDNA work

A

-mRNA will be comp to the target gene
-reverse transcriotase is added and uses free DNA nucleotides to make cDNA from the mRNA template
-single stranded cDNA is isolated by the hydrolysis of the mRNA using an enzyme
-double stranded DNA is formed from the cDNA using DNA polymerase
-giving a copy of the gene

28
Q

what is cDNA

A

-comp DNA to the mRNA

29
Q

how does using restriction enzymes to cut a section of DNA from the genome work

A

-restriction endonucleases/enzymes will separate the two strands of DNA at the specific base sequence - that is comp to their active site-
-cut the sugar phosphate backbone in an uneven way to give sticky ends or straight blunt ends
-each restriction sequence is palindromic - comp to one and other - read same in each direction

30
Q

what is the role of sticky ends

A

-result in one DNA strand being longer than the other
-makes it easier to insert the desired gene into another organims DNA
-easily for H-bonds with the comp base sequences on the other pieces of DNA that have been cut with the same restriction enzyme

31
Q

what are restirction enzymes/endonucleases

A

-class of enzymes found in bacteria
-recognise and hyrdolyse hydrogen bonds at specfic sequences of DNA

32
Q

how does using a gene machine to build a section of DNA using nucleotides work

A

-if sequence of AA is already known the sequence of comp base triplets can be found out
1. base sequence is fed into a computer once it has been checked for biosafety and secrutiy
2. nucloetides added step by step in the right order and joined in the correct place to prevent branching
3. short sections of DNA called olginucleotides are produced - 20 long - these can be joined by DNA polymerase to form longer fragments
4. no introns or non-coding info in the gene as it has been sequenced from the final protien - so already undergone splicing
5. PCR is used to replicate the gene and make it doubl stranded
6. sticky ends added
7. gene can be insterted into a vector

33
Q

why is using a machine often the preffered method to isolate DNA

A

-alot quicker than using lots of enzymes

34
Q

what is in vivo gene cloning

A

-in the living - in whole,organisms or cells
-DNA fragment is placed in a plasmid and relies on bacteria conjugation and replication to make a copy of the plasmid
-takes longer and requires screening as not all bacteria will take up the gene
-using maker genes and manipulating growth conditions can help determine if genes have been taken up and amplified by the organism

35
Q

what are the 5 stages of in vivio gene cloning

A

-desired gene is isolated using a restriction enzyme
-gene is inserted into a vector using a plasmid-
-recombinant plasmid is now tranaferred to host cells -transformation
-host cells are allowed to multiply and those that have taken up the genes are identified using a marker gene - indentification
-cloning/growing

36
Q

how does the 1st stage/isolation of the gene using a restriction enzyme work

A

-promoter region and terminator regions are added to the gne to make sure the gene can be correctly transcribed once in the host
-promoter - tells RNA polymerase where to start transcribing mRNA
-terminator - tells RNA polymerase to stop

37
Q

what is the 2nd stage/ gene is inserted into a vector

A

-plasmids - which are circular lengths of DNA, found in mos t bacteria that are seperate from the main DNA - contain genes for antibiotic resistance
-cut the plasmid with the SAME restriction enzyme to leave sticky ends - comp to DNA fragment and plasmid
-DNA ligase enzyme joins the two DNA fragments together - catalyse the condensation reactions that join sugar and phosphate group

38
Q

how can the gene be inserted into the plasmid wrongly

A

-gene can go in backwards
-plasmid can close back up - without gene in- sticky ends close

39
Q

how does the 3rd stage/ the recmobinant plasmid is transferred to the host cell work

A

-solution of calcium ions can be used to make the cell walls more permeable
-heat shock or electroporation (small electric shock) is used to make holes in the membrane which DNA can pass through
-some bacterial cells wont take up the plasmids
-only bacteria whihc now contain the recombinant plasmid will be able to express the gene and make the protein

40
Q

what are the 3 ways that stage 4/ identification using marker genes can be done

A

-using antibiotic resistant genes
-genes coding for fluorescent proteins
-genes coding for enzymes

41
Q

how does using antiobiotic resistance genes to identify genes work

A

-marker genes can code for antibiotic resistance
-colonies of bacteria are grown on an agar plate that contains the antibiotic
-only transformed genes with the resistant gene will survive
-they can then be selected

-take a copy of the agar with bacteria on
-transfer onto a plate that has an antibiotic on - those with resistant gene will not be killed
-restamp this and grow on another plate that has antiobiotic on
-the ones that are killed this time will be the ones resitant to the previous AB and not this one
-so can then look back at the original and identify which has resistance

42
Q

how does genes coding for fluorescent proteins as markers work

A

-gene from jellyfish that contains a green floruescent protein is insereted into a plasmid
-the gene to be cloned is inserted into the centre of the GFP gene
-restriction enzymes cut and put the gene in a vector - destroys the ability for the fragment to grow
-bacterial cells that have the recombinant pasmid - will not fluoresce
-bacterial cells with the non-recombinant plasmid - will fluoresce

43
Q

how does using genes coding for enzymes as marker genes work

A

-enzyme lactase can turn certain substances from colourless to blue
-the gene for this enzyme is inserted into a plasmid
-the DNA fragent is inserted in the middle of this gene to disrupt it
-the bacteria are then grown on an agar plate with the colourless solution
-the colonies which cannot turn the colourless substance bluw contain the recombinant plasmid

44
Q

how does stage 5 in in vivo cloning work

A

-genetic code is universal so bacteria can transcribe the DNA and transalte the mRNA to produce the protien
-the mechanism and machinery is the same in all organims
-a fermenter is used to grow multiple copies of the host cell which have been indentified as containing the copy of the recombinant plasmid
-the clones can then produce the protein coded for by the inserted DNA fragment

Biology - A-level (13 decks)

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