chapter 21 - manipulating genomes Flashcards
1
Q
Why do we compare genomes?
A
we compare genomes to :
- to understand evolutionary relationships
- understand genotype-phenotype relationships
- for epidemiology(disease analysis)
- synthetic biology(genetic engineering)
2
Q
Why are the studies of genotype-phenotype relations and epidemiology important?
A
- Analysing the genotype to predict the phenotype
- understanding disease will help better prevent it
3
Q
what is synthetic biology?
A
- designing and creating new biological molecules, systems and machines
- for example, making new enzymes to make them more efficient
4
Q
What is DNA profiling?
A
- identifying individuals by comparing their repetitive non coding base sequences
5
Q
What are the two uses of DNA profiling?
A
- forensic use
- medical use
6
Q
How is dna profiling used in forensics?
A
- 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
7
Q
How is dna profiling helpful in medical use?
A
- DNA profiling can be used for testing for specific combinations of alleles which can be used to diagnose genetic disease
8
Q
What is a genome?
A
- its the complete set of genetic material (genes + non coding DNA)that an organism has
9
Q
what is a proteome?
A
- the complete set of proteins that an organism can make
10
Q
What two techniques are used to construct dna profiles and what are their purposes?
A
- PCR, used to amplify dna
- electrophoresis, separation of the the dna fragments
11
Q
To produce a dna profile, dna must be:
A
- extracted (usinf PCR)
- digested using restriction endonucleases
- separated using electrophoresis
- hybridised with probes
- visualised in banding patterns
12
Q
What is the difference between dna profiling and dna sequencing?
A
- 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
13
Q
how is dna sequenced?
A
- 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
14
Q
why do we sequence dna and what is it used for?
A
- to predict amino acid sequences
- its used for understanding evolutionary relationships and in medicine(understand the antigens to make new vaccines)
15
Q
why is it easier to predict amino acid base sequences in simple organisms over more complex organisms?
A
- in more complex organisms, its harder to determine proteins from dna
16
Q
What are the two ways in which target genes are isolated and how?
A
- restriction enzymes, cuts the dna leaving sticky ends (unpaired bases)
- Reverse transcriptase, enzyme that does transcription backwards (MRNA to CDNA)
17
Q
What are the 3 steps to insert target genes?
A
- isolate target gene
- insert target genes into vector
- insert vector into bacteria
18
Q
What is the process of inserting target genes?
A
- 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
19
Q
What is a maker gene?
what is its use?
A
- genes that are paired with target genes to check if the vector has been inserted properly
- it tells us which bacteria have become transformed
20
Q
What are two examples of marker genes that can be used?
A
- UV fluorescence
- antibiotic resistance
21
Q
What is required for bacteria to fluorescence under uv and be able to survive in a culture with antibiotic?
A
- needed to have accepted the vector
22
Q
What is needed in order for the polymerase chain reaction to happen?
A
- dna sample
- free dna nucleotides
- primers
- dna polymerase
23
Q
what are primers and what are they used for?
A
- 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
24
Q
what is the method for the polymerase chain reaction?
A
- 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
25
What is gene therapy?
- its changing faulty alleles that cause genetic disease
26
give an example of diseases that are caused by both a dominant allele and a recessive allele
- dominant, huntingtons disease
- recessive, cystic fibrosis
27
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
28
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
29
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)
30
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
31
What are the main 3 uses of genetically modified organisms/
- agriculture
- industry and research
- medicine
32
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
33
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
34
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
35
What are the disadvantages of using genetically modified bacteria in industry and research?
- could mutate and infect humans
- could be used in war
36
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
