chapter 21 - manipulating genomes Flashcards
Why do we compare genomes?
we compare genomes to :
- to understand evolutionary relationships
- understand genotype-phenotype relationships
- for epidemiology(disease analysis)
- synthetic biology(genetic engineering)
Why are the studies of genotype-phenotype relations and epidemiology important?
- Analysing the genotype to predict the phenotype
- understanding disease will help better prevent it
what is synthetic biology?
- designing and creating new biological molecules, systems and machines
- for example, making new enzymes to make them more efficient
What is DNA profiling?
- identifying individuals by comparing their repetitive non coding base sequences
What are the two uses of DNA profiling?
- forensic use
- medical use
How is dna profiling used in forensics?
- a sample of DNA is taken from a crime scene and suspects
- the DNA is amplified using PCR
- DNA is then labelled using a marker
- the gel electropheresis is run
How is dna profiling helpful in medical use?
- DNA profiling can be used for testing for specific combinations of alleles which can be used to diagnose genetic disease
What is a genome?
- its the complete set of genetic material (genes + non coding DNA)that an organism has
what is a proteome?
- the complete set of proteins that an organism can make
What two techniques are used to construct dna profiles and what are their purposes?
- PCR, used to amplify dna
- electrophoresis, separation of the the dna fragments
To produce a dna profile, dna must be:
- extracted (usinf PCR)
- digested using restriction endonucleases
- separated using electrophoresis
- hybridised with probes
- visualised in banding patterns
What is the difference between dna profiling and dna sequencing?
- dna profiling, identifying individuals by comparing their repetitive non coding base sequences
- dna sequencing, is determining the precise order of nucleotides in a dna molecule
how is dna sequenced?
- pcr is conducted
- some of the free nucleotides in pcr have been modified in two ways:
- when they bond to a dna strand they terminate polymerisation
- they are fluorescently coloured
- new dna strands stop growing when a terminator base is added (PCR is interupted)
- this results in every possible chain length being produced
- lasers detect the final base on each chain
- the sequence of dna bases can therefore be worked out
why do we sequence dna and what is it used for?
- to predict amino acid sequences
- its used for understanding evolutionary relationships and in medicine(understand the antigens to make new vaccines)
why is it easier to predict amino acid base sequences in simple organisms over more complex organisms?
- in more complex organisms, its harder to determine proteins from dna
What are the two ways in which target genes are isolated and how?
- restriction enzymes, cuts the dna leaving sticky ends (unpaired bases)
- Reverse transcriptase, enzyme that does transcription backwards (MRNA to CDNA)
What are the 3 steps to insert target genes?
- isolate target gene
- insert target genes into vector
- insert vector into bacteria
What is the process of inserting target genes?
- cut the dna using restriction enzyme which will leave sticky ends
- use the same restriction enzyme to cut the plasmid open
- this allows the sticky ends to be complementary
- dna ligase reforms phosphodiester bonds
- this forms recombinant dna(dna from more than one source or organism)
- electroportation is used to increase the permeability of the bacterial cell wall, meanings its more likely to take up the recombinant plasmid
What is a maker gene?
what is its use?
- genes that are paired with target genes to check if the vector has been inserted properly
- it tells us which bacteria have become transformed
What are two examples of marker genes that can be used?
- UV fluorescence
- antibiotic resistance
What is required for bacteria to fluorescence under uv and be able to survive in a culture with antibiotic?
- needed to have accepted the vector
What is needed in order for the polymerase chain reaction to happen?
- dna sample
- free dna nucleotides
- primers
- dna polymerase
what are primers and what are they used for?
- they are a short sequence of dna that are complementary to the start of dna sample
- they are used to select which part of dna is copied
what is the method for the polymerase chain reaction?
- dna placed in thermocycler(cycles three temperatures)
- first 95 degrees, which breaks the h- bonds and makes the dna single stranded
- then cool to 55 degrees, allows primers to bind (via complementary base pairing), dna becomes double stranded
- then heat to 70 degrees, dna polymerase adds complementary nucleotides and forms phosphodiester bonds
What is gene therapy?
- its changing faulty alleles that cause genetic disease
give an example of diseases that are caused by both a dominant allele and a recessive allele
- dominant, huntingtons disease
- recessive, cystic fibrosis
how is gene therapy used to treat someone with a dominant allele?
- sufferer will be hetrozygous(different alleles)
- they already have the functional allele
- the dominant allele is silenced
- use a vector to add a dna fragment into dominant allele
- dominant allele wont be transcribed
- recessive allele expressed
How is gene therapy used to treat someone with a recessive allele?
- sufferer will be homozygous(same allele)
- use a vector to add the functional allele to dna
- dominant allele will be expressed
What are the two types of gene therapy?
- germ line therapy, changes the alleles of gametes (offspring inherit changes)
- somatic gene therapy, changes the alleles of body cells(non - gametes) (offspring don’t inherit changes)
What are the possible problems with gene therapy?
- alleles may be inserted into wrong locus
- could silence wrong gene by mistake(tumour surpressor gene cause cancer)
- gene could be over expressed
- use of gene therapy could be used for non medical uses
What are the main 3 uses of genetically modified organisms/
- agriculture
- industry and research
- medicine
How are genetically modified organisms used in agriculture?
what is the advantage of these uses?
- a protein is expressed from a bacteria which is toxic to pests and so fewer soya plants are eaten. - advantage - use less chemical pesticide and more efficient food chain
- gene from corn plant put into rice plant which will express vitamin A. - advantage - prevents blindness caused by vitamin A deficiency
What are the disadvantages of using genetically modified organisms in agriculture?
- monoculture of crop has low genetic diversity meaning they are more susceptible to disease
- farmer has to buy seeds every year
- decrease in biodiversity
How are genetically modified organisms used in industry and research?
what is the advantage of these uses?
- making enzymes. - advantage - reduces energy and cost, faster and cheaper production
- transformed pathogen to treat disease by attacking other pathogens without infecting humans - advantage - treats disease, pathogen wont develop resistance
What are the disadvantages of using genetically modified bacteria in industry and research?
- could mutate and infect humans
- could be used in war
How are genetically modified organisms used in medicine?
what is the advantage of these uses?
- transform bacteria to express protein
- mammals can also be used to produce useful products in their milk
advantages - - makes human proteins
- cheaper and easier than making proteins synthetically
