Topic 8 Flashcards
1
Q
What is substitution of bases?
A
Nucleotide in section of DNA is replaced by another nucleotide that has a different base
2
Q
What are the potential consequences of base substitution?
A
-formation of one of the three stop codons that mark the end of a polypeptide chain. Causing the production of polypeptide coded to be stopped prematurely, changing the final protein structure and function significantly
-changes formation of codon, meaning it forms a different amino acid= structural change= function change
-forms a different codon but still produces same amino acid as the genetic code is degenerate= no effect on structure/ function of protien
3
Q
What is base deletion?
A
Loss of nucleotide base from DNA sequence
4
Q
What is the consequence of a base deletion?
A
A frame shift= gene read wrong= alters coded information= so triplets will be different= forming different amino acids= non functional protein = alter phenotype
-base deletion at start of sequence could alter every triplet in the sequence. = large impact
-base deletion near end of sequence has a smaller impact as most of the triplets coded for by the gene are read correctly (but can still cause changes protein)
5
Q
What is addition of bases?
A
Extra base is inserted into sequence . There is a frame shift (to the right), but if 3 bases are added there won’t be a frame shift = so less impactful on proteins final complete form than if it were a frame shift
6
Q
What is base duplication?
A
Where one or more bases are repeated, causing frame shift to the right
7
Q
What is base inversion?
A
Group of bases became separated from DNA sequence and rejoin at the same position but in inverse order=change amino acids sequence
8
Q
What is base translocation?
A
Group of bases separated from the DNA sequence on one chromosome and are inserted into the sequence of a different chromosome = abnormal phenotype = can cause cancer and reduced fertility
9
Q
What are spontaneous mutations?
A
-permanent changes in DNA that occur without any outside influence
10
Q
What causes an mutation?
A
-spontaneous mutation
-mutagenic agents
11
Q
What are the examples of mutagenic agents?
A
- High energy ionising radiation: distrupts structure of DNA
- Chemicals: alters structure of DNA/ interferes with transcription
12
Q
What are the benefits and costs of mutation?
A
-produce genetic diversity for natural selection and speciation
-harmful and produce organisms less suited to its environment
-in body cells, cause disruption of normal cellular activity {cell division} = cancer
13
Q
What is cell differentiation?
A
Process each cell develops into a specialised structure suited to its role carried out
14
Q
Why does cell differentiation occur in multicellular organisms?
A
- different cells have different structure enzyme/ protein, so a type of cell might be more adapted to carry out particular role.
(not a single cell can provide best conditions for all function )
15
Q
How does cell specialisation occur?
A
-all cells in organism contain the exact same genes . So all cells are capable of making everything the body produces
-so each cell can express certain genes in a cell at any time
16
Q
What is cell specialisation?
A
Where certain genes are expressed in a cell
-some are permanently expressed (enzymes for respiration)
-some are permanently not expressed
(Gene for insulin lining small intestine)
-some are expressed and not expressed when needed
17
Q
Why do differentiated cells differ from eachother?
A
They Produce different proteins.
These protiens are coded for by genes expressed
18
Q
What are totipotent cells?
A
Cells that can mature into any body cell
(Fertilised eggs) (cells derived from fertilised eggs)
19
Q
What is totipotency?
A
Ability of a single cell to divide and produce all the differentiated cells in an organism (totipotent cells)
20
Q
What are the ways in which genes are prevented from being expressed?
A
-preventing transcription = stop mRNA production
- preventing translation
21
Q
What are stem cells?
A
Cells that are able to differentiate into other cells
-undifferentiated dividing cells that occur in animal tissue and constantly need to be replaced
-undergo self renewal
22
Q
What is the process of self-renewal?
A
Where stem cells divide to form identical copies of themselves
23
Q
Where do different stem cells originate from?
A
-Embryonic stem cells: come from embryos in early stage of development. (Can differentiate into any cell)
-umbilical cord blood stem cells: from umbilical cord blood (similar to adult stem cells)
-placental stem cells: found in placenta (develop into specific cells)
-adult stem cells: found in body tissues of fetus through to adult (specific to organ/ tissue there from, produce cells to maintain / repair tissue)
24
Q
What are the different types of stem cells?
A
-Totipotent stem cells: found in early embryo. Can differentiate into any type of cell
-pluripotent stem cells: (when a zygote divides and becomes more specialised/ embryonic stem cells) Found in embryo, can differentiate into almost any type of stem cells
- multipotent stem cells: in adults, differentiate into limited number of specialised cells (adult stem cells, umbilical cord blood cells)
-unimportant stem cells: differentiate into single type of cell. Derived from multipotent stem cells, in male adult tissue. (Cardiomyocytes)
25
What are induced pluripotent stem(iPS) cells?
-produced from unipotent stem cells
So can be almost any body cell.
Unipotent stem cell , are genetically altered in a laboratory to make them aquire characteristics of embryonic stem cells by inducing genes and transcriptional factors within the cell to express those characteristics. They are capable of duplication to produce limitless supply of (iPS)
26
How can pluripotent stem cell be used to treat human disorders?
Used to regrow tissues that have been altered by accident or disease
(Burns and wounds) (type 1 diabetes for Beta cells of pancreas) (muscular dystrophy) (osteoporosis for bone cells)
27
What are the general principles involved in controlling the expression of a gene?
-transcription factors in the cytoplasm have a site that binds to specific base sequence of DNA in nucleas . when binded, causes DNA to begin transcription process (actives gene, so RNA synthase starts binding at promote region to form mRNA)= protein sysnthesis
When genes not expressed , the site on transcriptional factor that binds to DNA is not active. So cannot cause transcription and polypeptide synthesis
28
How does oestrogen affect gene transcription?
Oestrogen is lipid soluble molecule, so diffused through phospholipid portion of cell surface membrane
-oestrogen then binds with site on receptor molecule of transcriptional factor , which shape is complimentary to oestrogen
-this changes shape if DNA binding site on transcriptional factor binds, that now can bind to dna (activated). Si can enter nucleas through nuclear pores and bind to specific base sequences on DNA= gene activation= stimulate transcription
29
What is epigenetic?
How environmental influences alter genetic inheritance of an organisms and their offspring without changing the base sequence of DNA
(Environment affects genome and it can be inherited)
30
What is the epigenome and its features?
*The chemical tags that from a second layer which covers DNA- histones complex.*
-is flexible (not fixed like DNA code) to the environment as the tags respond to environmental changes.
-Acts as cellular memory: an accumulation of of signals it has received in its lifetime (from mother-environment)
-determines the shape of the DNA-histone complex.
[that causes epigenome to inhibit/activate specific sets of genes]
31
How does the environment signal stimualte genes to become active?
Send signals to stimulate proteins to carry its message inside the cell where it’s passed by a series of other proteins into the nucleas. That’s passed to a specific protein that can attach to Semitic base sequence on DNS= acetylation, methylation
32
What is the DNA-histone complex (chromatin) and how does it alter genetic inheritance expression?
DNA wrapped around proteins called histones
Genes expressed: DNA-Histone complex is less condensed . So DNA is accessible by transcription factors = production of mRNA. Caused by increased histone acetylation and decreased DNA methylation (called euchromatin)
Genes not expressed: DNA-history complex is more condensed. So DNA is not accessible by transcription factors ≠ mRNA production (inhibits transcription) . Caused by decreased histone acetylation or increased methylation of DNA (called heterochromatin)
33
How does decreased acetylation of histones cause the gene to be unexpressed?
-acetyl group from acetylcoenzyme is transferred by deacetylation and is transferred to the histones. (That occurs less so less positive charge removed) Which increases their positive charge = attraction to DNA phosphate group= stronger association=less for transcription ti be activated
34
How does increased DNA methylation Cause less gene expression?
Adds methyl group to cytosine base on DNA
-prevents transcriptional factors binding to DNA
-attracts proteins that condense DNA-histone complex (induces deacylation of histones). So DNA is inaccessible to transcriptional factors
35
How does epigenetic inheritance take place?
-in rats good maternal behaviour transmits epigenetic information onto their offspring DNA without passing through egg or soerm
-in pregnancy, when mother has gestational diabetes , fetus is exposed to high glucose concentrations, which cause epigenetic changes in daughters DNA. Increase chances she develops it herself
Some of the epigenetic tags might escape the procces to erase epigenetic tags to return cells to genetic clean state. So pass unchanged from offspring
36
How does epigenetic cause disease ?
-can cause activation of genes that cause cancer
-inactivates normal active genes which then causes rise to disease
(Promotor region is methylated which cause genes to switch off = less genes can be activated to repair DNA and prevent cancer= cancer development)
37
How are diseases treated with epigenetic therapy?
Use of drugs that inhibit certain enzymes involved in histone acetylation or DNA methylation.
-for cancer: cells must be specifically targeted, as they could activate/inhibit genes transcription on normal cells, making them cancerous
-used in diagnostic tests: can identify levels of DNA methylation and histone acetylation at early stages. So allow diseases (cancer/ brain disorder) to get early treatment to get better chance of being cured
38
How does RNA interference affect translation process?
-an enzyme cuts largely double stranded molecules of RNA into smaller sections called small interfering RNA (siRNA)
-one of two strands of siRNA combine with an enzyme
-siRNA molecule guided enzymes to messenger RNA molecule by pairing up its bases with complimentary ones in section of mRNA molecule
-once in position, enzyme cuts largely double mRNA into smaller sections. Meaning it can no longer be translated into a polypeptide.≠ gene not expressed, so it is blocked
39
What are benign tumours?
-can grow to a large size
-grow very slowly
-cell nucleus has relatively normal appearance
-cells are often well differentiated (specalised)
-produce adhesion molecules that make them stick together , so remain in tissue they arise= primary tumours
-surrounded by a capsule of dense tissue and so remain as a compact structure
-less lethal but can disrupt vital organ functioning
-have localised effects on the body
-usually removed by surgery alone
-rarely reoccur after treatment
40
What are malignant tumour?
-can grow to large size
-grow rapidly
-cell nucleas is often larger and appears darker from abundance of DNA
-cells became de-differentiated (unspecialised)
-perform metastasis (spread to other parts of body as they lack adhesion molecules) = secondary tumours
-not surrounded by capsule , so can grow finger like projections into surrounding tissue
-more lethal, as abnormal tumour tissues replaced normal tissues
-have systematic affect (weight loss, fatigue)
-removal usually involves radio therapy, chemotherapy and surgery
-more frequently reoccur after treatment
41
What are and How do proto-oncogenes cause cancer?
-they stimulate cell to divide by activating gene when growth factors attach to a protein receptor on its cell surface
-can cause cancer when they are (activated) mutated into an oncogene (potentiallyby hypomethylation of DNA). Which can permanently activate receptor protiens on cell surface membrane, so cell division is permanent switch in absence of growth factors. Or might code for growth factor that’s produced in excessive amount= stimulate cell division
Hi Denise, yesterday we discussed cancer and briefly touched on proto-oncogenes and how they can be mutated into oncogenes which cause cancer.
Example:, the kidneys produce erythropoietin (EPO) which is a growth factor
- This acts on bone marrow multipotent stem cells to stimulate differentiation into red blood cells
- It does so by stimulating transcription of the proto-oncogene JAK2
- In polycythaeamia vera, there is a JAK2 mutation, meaning it is always switched on, irregardless of whether EPO is present or not
- This causes excessive unrestrained mitosis and development of red blood cells
- They thicken the blood increasing risk of clots such as strokes or heart attacks.
42
What are and how do tumour suppressing genes cause cancer?
-slow down cell division, repair mistakes in DNA, and performs apoptosis (types: TP53, BRCA1/2)
-cause cancer when inactivated (potentially by hypermethylation of DNA. So it stops inhibiting cell division and causes cells to grow uncontrollably. So mutated cells formed are structurally and functionally different (most mutations are acquired not inherited)
43
How does oestrogen play a role in causing breast cancer?
-oestrogen activates genes by binding to transcriptional factors, that then binds to promotor region that activates transcription. This then might activate a gene that controls cell division (proto-once genes to oncogenes)-causes breast cancer/tumour= white blood cells drawn to tumour increase oestrogen production-> more tumour development
44
What is bioinformatics?
The science of collecting and analysing complex biological data such as genetic codes. It utilizes computers to read, store and organise biological data at a faster rate. Uses algorithms (mathematical formulas) to analyse and interpret biological data.
45
What is whole-genome shotgun sequencing?
-cuts DNA into fragments that have overlapping base sections
-computer algorithms are used to align overlapping segments that then assemble the entire genome
46
What are the medical advances that have been made as a result of DNA sequencing?
-quickly identify single nucleotide polymorphism (SNPs) found in human genome. Which are single base variations in genome that are associated with disease and other disorders. = early intervention to treat them.
-can establish evolutionary links between species
47
What is a proteome?
All proteins produced in a given type of cell (cellular protein) or organism (complete protein) at a given time under specific conditions
48
Why are determining proteome of simpler organisms easier than complex?
-majority of prokaryotes have one circular piece of DNA that is not associated with histones
-non of the none-coding portion of DNA that are typical of eukaryotic cells
49
Why is determine proteome of simpler organisms like bacteria usefall?
-identify proteins that act as an antigen on surface of human pathogen. That can be used in vaccines with appropriate dosage against disease causing pathogen
50
What are the difficulties with determining the genome and proteome of a complex organism?
-genome: technology is not advanced enough to produce precise number of total genes, and all of individuals have different base sequences on DNA, so DNA called will differ slightly from others DNA
-proteome: genome contains non-coding genes, and other that have. Role in regulation of toner genes.
51
What are the stages in producing genetically modified organism to make a protein using DNA technology?
1-ISOLATION of DNA fragments with the gene for desired protein (using reverse transcriptase, restriction enzymes [restriction endonuclease] , gene machine)
[1.5]- cloning DNA using PCR- in vitro gene cloning
(2) INSERTION of DNA into a vector (plasmid)
(3) TRANSFORMATION (transfer) of vector into suitable host cell (bacteria)
(4) IDENTIFICATION of host cells (bacteria) that have successfully taken up ‘wanted gene’ using markers (antibiotic resistance, fluorescent, Enzyme marker)
(5) GROWTH/CLONING of the population of host cells identified as having wanted gene (after killing other host cells that did not obtain wanted gene) [fermentors]
52
How is reverse transcriptase used to isolate the wanted gene?
Wanted mRNA is extracted from the cell
Acts as a template where single stranded DNA (cDNA) is formed using reverse transcriptase
cDNA is isolated by hydrolyses of mRNA with enzyme?
Double stranded DNA is formed on template of cDNA using DNA polymerase
53
How is restriction endonuclease used to isolate the wanted gene?
Cuts double stranded DNA at specific sequences of bases (recognition sequence)
Hpal restriction endonuclease performs a straight cut between opposite base pairs. that produces blunt ends (have no single strand and difficult to insert)
Hind III restriction endonuclease performs staggered cuts on palindrome sequence (between 1st, 2nd base and 2nd, 1st last base) which produces sticky ends (exposed unpaired bases)
54
How is a gene machine used to isolate the wanted gene (and then create genetically modified organisms)?
-desired amino acid sequence in protien is determined and sequence of mRNA nucleotides (codons) without introns are Determined. Then complementary DNA triplets are worked out for the ‘wanted genes’
-fed into computer (checked for Biosafety and biosecurity)
-computer synthesises small overlapping oligonucleotides which are assembled into ‘wanted gene’
[creating genetically modified organisms via later stages]
-gene then can be amplified by PCR (polymerase chain reaction)? Or inserted into vector , into host cell to clone to produce large amounts of gene
-then checked using standard sequencing technique , those with errors are rejected
55
What is the process of inserting a gene into a vector?
DNA fragment has a promote region and a terminator region attached. To attach RNA polymerase and transcription factors. So it is expressed only in intended cells
Vector (bacterial plasmid) is removed from bacteria
Restriction endonuclease cuts using same restriction endonuclease used to cut out DNA fragment, at the same recognition sequence, on genes in vectors (antibiotic resistance genes). to produce complementary sticky ends to DNA fragment sticky ends
-DNA fragment and plasmid opening is spliced together using DNA ligand that creates phosphodiester bonds via a condensation reaction which forms recombinant plasmids
(But plasmid can be unchanged)
56
What is the procces of transferring a recombinant vector into a host cell (transformation)?
-Host cell (bacteria) and vector (plasmid) are added into calcium solution .
-The ions and changes in temperature (lowering culture temp and then raising temp) make the host cell permeable to the vector.
- some of the host cells will take up the vector
57
What are the reason why not all bacteria cells posses DNA fragments with desired gene?
(Few as 1% take up vector when mixed with host cell)
(Some plamsids have closed without in incorperating DNA fragment)
(DNA fragments ends join together to form own plasmid)
-so don’t take up plasmid?
-host cell not take up vector
58
How are host cells containing plasmid with wanted gene identified using antibiotic resistance marker gene?
Add bacteria to agar plate with antibiotic (ampicillin), so only bacteria that have taken up plasmids will survive (have antibiotic resistance) .
-then use replica plating (replicating the plate) to determine bacteria that are sensitive to other antibiotic , which are the bacteria with ‘wanted gene’
(replicated bacteria plates contain antibiotic, so only plasmids with both antibiotic resistance gene survives)
59
How are host cells containing plasmid with wanted gene identified using fluorescent markers?
-transfer gene from jellyfish into plasmid that can then produce GFP (green fluorescent protein)
-Insert wanted gene into middle of GFP . Then transform into bacteria
bacteria which uptake wanted gene will not glow. Whilst those with at don’t have wanted gene will glow
So those that won’t glow have wanted gene
(Means no colonies are killed , no need for replica platting, faster method of identifying (using microscope)
60
How are host cells containing plasmid with wanted gene identified using enzyme markers?
(Similar process for using fluorescent markers)
Enzyme (Lactase) gene is added to vector
Then wanted gene is added to enzyme (lactase) gene
Add bacteria onto agar plate with colourless substrate
Bacteria with wanted gene do not produce enzyme so don’t act on substrate they don’t change colour of surrounding substrate
Bacteria without wanted gene produce enzyme, act on substrate and change the substrate colour (for lactase, to blue). So these can be discounted
So bacteria that don’t change colour contain ‘wanted gene’
61
How does the polymerase chain reaction clone fragments of DNA?
-DNA fragments , primers and Taq polymerase placed in a vessel in the thermocycler. Then it is heated to 95 degrees Celsius to break hydrogen bonds between DNA and so strands separate
-temperature reduced to 55 degrees Celsius that causes primers to anneal to complimentary bases at ends of DNA strands (also prevent speedsters strands rejoining)
-temperature is increased to 72 degrees Celsius , which is optimum temperature for Taq polymerase to add complementary nucleotides , starting at the primers
[yield from one DNa strand is two copies, that is increased exponentially every time . E.g, 2,4,8,16]
62
How is PCR different from natural replication?
-only replicate short DNA sequences but not entire chromosomes in natural process
-primers are needed to start process
-process of heating and cooling is needed in PCR to seperate and bind strands of DNA, which is done on natural replication by DNA helicase enzyme
63
What is required for the polymerase chain reaction?
-DNA polymerase: Taq polymerase from thermophilic bacterium *Thermus aquaticus*
-Free DNA nucleotides: containing 4 bases
-Primers: short single stranded DNA that have complimentary base pairs to bases at start of DNA Fragments, to allow Taq polymerase to replicate the DNA
64
What are the advantages to using PCR / in vitro gene cloning?
-it is extremely quick (in vivo take many days/ weeks to produce same quantity of DNA)
-it does not require living organisms
65
What are the advantages to using in vivo/ vectors for gene cloning?
-useful for introducing a gene into another organism (via gene therapy)
-involves little risk of contamination (in vitro cloning needs pure sample as contaminant DNA will also be multiplied and can cause false results)
-is very accurate (DNA copied has few errors)
-cuts out specific gene
-produces transformed bacteria that can be used to produce large quantities of gene product :(e.g proteins) used for medical and commercial use
66
What are the benefits of using recombinant DNA technology?
-microorganisms provide a range of substances (e.g antibiotics, hormones to treat diseases and disorders)
-control pollution (e.g destroy harmful gases, digest and break oil), then to avoid unwanted damage, suicide gene can be incorporated to destroy themselves once the pollution is managed
-form GMP to produce specific substance in certain organ of plant. Such as for plant pharming to Produce, drugs, antibodies to pathogen and toxins. Produce and manufacture antigens that can be injected into human to induce natural antibody production
-GMP provided financial and environmental advantages. Makes plant more tolerable to extreme conditions/ selection pressures. Can grow and survive in different places
-help prevent certain diseases ( add gene such as for vitamin A to crop, golden rice, to reduce vitamin A differently
-can produce expensive drugs, antibiotics, hormone and enzymes relatively cheaply
-used in gene therapy to cure certain genetic disorders (cystic fibrosis)
-genetic fingerprinting is useful for forensic science (parentity cases , criminal identification , evolutionary relationships)
67
What are the risks of using recombinant DNA technology?
-impossible to predict with complete accuracy what the ecological consequences will be on the environment
-recombinant gene might pass from organism it was slaves in. To a completely different one
-might have consequences for the metabolic pathways within that cell. Leading to metabolic malfunctions, cancer or creating new form of disease
-GMO bacteria might spread antibiotic resistance to harmful bacteria
-potential harm of genetically engineered gene mutating (GMO could became a pathogen)
-unknown long term consequences of introducing new gene combinations
-financial consequences of growing GMO domestically than abroad . Destabilise foreign markets that rely on crops to make income
-encourages genes being introduced for intelligence , muscles, cosmetic improvements and facial features, raises difficult ethical questions
-potentially lead to eugenics
-financial costs might be unjustified
-individual might exchange DNA sample maliciously in genetic fingerprinting leading to wrongful convictions
-immoral to tamper with all genes, against natural selection?
-individuals and company can patent and own a gene (so human genome difficult to use)
68
What are DNA probes?
Short, single stranded length of DNA that is complementary to base sequence of target allele, that identify the precise location of a gene
Contains labels
[radioactive -have nucleotides with (32)P, which is visualised on an X-ray film, exposing radioactivity- ]
[fluorescent -emit light (fluoresce) under certain conditions , e.g probe bound to DNA target. So visualised under UV light- ]
69
How are DNA probes used to identify particular allele of a gene?
1-DNA probe made, which has base sequence complimentary to part of DNA base sequence that makes up the allele of gene wanted to be found
2-double stranded DNA is separated into two strands
3-[DNA hybridisation] separate DNA are mixed with probe and binds to complimentary DNA base sequence
-sight probe binds to can be identified by radioactivity / Florence probe emits
70
What is the process of DNA hybridisation?
1.( denaturation) DNA/ RNA molecule is separated by heating it until it is separated into two complimentary strands
2. (Annealing) cooling DNA/RNA, so complimentary DNA and other complimentary single stranded sections of DNA are annealed to DNA/ RNA single strand
71
How are specific alleles of genes located?
-sequence of nucleotides determined using DNA sequencing techniques or genetic library store
-fragment of DNA produced which has sequence of bases commentary to mutant allele trying to be located
-fragment is amplified by PCR
-probe is made by attaching a marker to DNA fragment
-DNA from person suspected of having mutant allele is heated and separated into two strands (denaturation)
-separated strands cooled in mixture contains DNA probes, where if mutant allele is present , the probes will anneal to DNA strand. DNA
-DNA is washed clean of any unattached probes
-remaining hybridised DNA is fluorescently labelled with the dye attached to probe and so can be detected by shining light onto fragment, causing dye to fluoresce , which can be seen using a special microscope
[if not probe not present, DNA strands recombined together, then will not fluoresce]
72
How is the DNA microarray process used to genetically screen individuals?
-hundred of different probes placed on a fixed glass slide in an array pattern
-Donars DNA sample is added to microarray and anneal to the complementary fixed probes,
-array is washed and then scanned to identify faulty / mutated alleles (or also oncogenes, mutations that inactivate tumour suppression genes ). Making it possible to test simultaneously for many different genetic disorders by detecting fluorescence that occurs where binding has taken place
This allows for individuals to make informed lifestyle choices and decisions to reduce risk of getting disease and avoid mutagens . Adler as check themselves more regularly or opt for surgery .
(Such as for tumour suppressing genes, as both need to be inactivated for cancer to form, os can identify their increased risk of getting cancer with age, which can be detected by screening)
73
How can genetic screening be used for personalised medicine?
Doctors can provide advice and health care based on individuals genotype. Provide evaluation of the effectiveness of the drug in treating the condition
This can be used to produce required amount of drugs for desired outcome , that saves money in wasted/ oversubscribed drugs
-avoids medications that can cause harm, and avoids raising false hopes something will work when it actually does not
EXP: screening diabetic individuals for anyone who might have genotype that increases risk (after taking vitamin E) of cardiovascular disease . So can choose to not take vitamin E to reduce this risk
74
How can genetic screening be used for genetic counselling?
Helps individuals to understand result and also implications to make appropriate decisions. For themselves and their offspring
(Informs is visuals in emotional , physiological, medical, social and economic consequences)
Genetic screening provides basis for informed decisions
(for cancer screening help detect oncogene mutations , gene changes that can be used to provide best treatment for patient and single cancer cells. To determine best course of treatment and prospect of survival)
75
What are the requirements for genetic fingerprinting?
-DNA contains many repetitive non coding bases called variable number tandem repeats (VNTRs), which has an unique pattern to each individual (apart from twins)
76
How are genetic fingerprints made?
(1) DNA is extracted by separating the rest of the cell from the sample. Which is then amplified using PCR
(2) DNA are cut into fragments using restriction endonuclease
(3)gel electrophoresis separates DNA fragments. Southern blotting used to transfer DNA onto nylon sheet . Then separated into single strands by immersing gel in alkali.
(4) radioactive / fluorescence DNA probes binds to VNTRs under specific conditions like temperature and pH. Which is then carried out using different probes that bind to different DNA sequences
(5) X ray film place over nylon membrane . Film is exposed using radiation from the radioactive probes ( or located visually) which correspond to position of DNA fragments separated during electrophoresis that produce a series of bars
77
How are DNA fragments separated by gel electrophoresis
DNA samples are placed into wells cut at cathode end of the gel on agarose gel. And then covered in buffer solution , causing an electric current to pass through solution for about 2 hours. So dna fragment diffuse through gel to opposite electrode . With shorter lengths of DNA moving faster and further than longer DNA , which get caught up in gel and slowed
(Can be used in Sanger method for DNA sequencing and genetic fingerprinting)
78
How can genetic fingerprinting be interpreted?
-two samples are visually checked
-then they are passed through an automated scanning machine, to calculate the lengths of the DNA fragments from the bands (determined by how far the fragments have traveled in distance during electrophoresis)
-odds are calculated of someone else having an identical fingerprint
-closer match between two patterns , the greater the probability that the two sets of DNA come from the same person
79
How can DNA fingerprint be used for genetic relationship and variability?
For paternity cases: Each band on a DNA fingerprint of an individual (child) should have a corresponding band in one of the parents, parents DNA fragments
Genetic variability: population whose members have very similar genetic fingerprints has little genetic diversity, vice versa
-can be used to identify identical twins
80
How can DNA fingerprint be used for forensic science?
Identify if a person is likely to have been at the crime scene
It can not be used to prove that the individual is committed the crime:
-could have been DNA left on some other occasion
-belonged to a very close relative
-DNA sample might have been contaminated after the crime
-does not always comply to interpretation process: the DNA producing the banding pattern might not be randomly distributed in the community(e.g religious / ethnic groups), so it increases the probability that the suspects DNA might might match someone else’s
81
How can DNA fingerprint be used for medical diagnosis ?
Used to identify the chances of individuals developing the symptoms of the diseases and when they might occur
(E.g, DNA sample from individual with allele for Huntington disease can be inteprted on a genetic fingerprint, compared with various forms of disease and those without the disease. Identify if there is an genetic stutter, and if there is how much repeats there are of AGC base sequence ,more repeats more likely to develop disease, 53 repeats and they’ll develop it earlier)
-identify nature of a microbial infection by comparing the fingerprint of the microbe found in patients with that of known pathogens
82
How can DNA fingerprint be used for plant and animal breeding?
-prevent undesirable inbreeding during breeding programmes on farms/ zoos
-identify plants / animals that have particular allele of a desirable gene, so can be selectively bred
-determine paternity in animal and so establishing pedigree (family tree) of an individual
