Genetic technology Flashcards

Question

Describe insect resistant crops-Bt crops

Answer 1

E.g. Bt cotton, Bt maize *Bt cotton protected against boil weevils *Bt maize protected against corn borer caterpillars *Corn borer eats leaves and burrows into stalk →Plant cannot support the ears of corn *Gene for Bt toxin from bacteria bacillus thuringiensis inserted into maize/cotton *Lethal to insects but not other animals *Crops able to produce own insecticide

Answer 2

*Increased yeilds *Only kills specific insects that eats it and does kill beneficial insects E.g. pollinators/bees/predators of pests →Conserve biodiversity/food web *Less pesticide used →Reduce risk of pesticide affecting non-target species in the same enviroment *Less risk of harm from spray drift/pesticide residues on food

Answer 3

e.g. tabacco, oil seed rape,roundup ready soybean *Gentically modified to be resistant to herbicides coontaining glyphosphate (e.g. roundup) *Glyphosphate inhibits enzymes involved in amino acid synthesis *Gene from bacterium agrobacterium coding for enzymes with the same function that are not affected by glyphosphate *Herbicide resistant gene acts as marker gene →Herbicides will have no effect on plant, only the weeds

Answer 4

*Can control/Kill weeds →Reduce competition →Increase yeild *Less manual weeding needed

Answer 5

*GM production cost is expensive →Does it outweigh benefits?It has only 1% success... *Monopoly/too much power held by multinational companies *people may avoid/refuse to buy for GM food *No long term studies done on effects on human health *Possible allergic reactions in humans/adverse effects on the immune system Enviromental: 1. Intensive use of herbicides →High toxicity of more herbicide left after use →Harmful to humans 2. Cross pollination with wild plants/organic crops →Result in new more resistant weeds="superweeds" →Superweeds are selected for by herbicide use →Outcompete and lose traditional varieties of plants →Loss of genetic diversity →Cause effect on rest of food chain=less food or shelter for other species Solution:Use sterile seeds/plants to avoid superweeds Economic: *High cost of GM seeds →Seeds are sterile and canot use own seed →Too expensie for people to buy/farmers to sell →Diffucult for farmers in developing countries to obtain GM seed →Might reduce efforts to relieve poverty →Under-developed countries become more dependant on other countries *Cost of herbicides: →Cost of problems with pollution →Cost of human health problems →Loss due to contaminated crops of organic farms

Answer 6

Function: To separate fragments of DNA according to length OR to seperate diff proteins according to mass/charge.

Answer 7

1. Agarose gel (DNA) or Polyacrylamide gel (proteins) with wells: Diff gel, diff impedance Even spaces between the gel molecules so DNA/protein can move within gel properly Wells to load DNA/Protein 2. Electrodes + electric feild: Molecules with net negaive charge will move towards positive electrode 3. Buffer solution mantain constant pH 4. Loading dye Visible dye to track DNA migration →Ensure electrophoresis is stopped before DNA/protein runs off the gel 5. Staining agent DYE that stains the colourless DNA/protein e.g. ethidium bromide causes DNA to fluoresce under UV light 6. DNA ladder or protein ladder Has DNA fragments or susbtances of known lengths/mass →Can estimate the length/mass of samples by comparing them to the ladder 7. Gene probes (DNA) To locate a specific DNA sequence

Answer 8

1. Obtain sufficiet quantity of DNA *DNA can be amplified using PCR or gene cloning in bacteria 2. Cut DNA into fragments using restriction enzymes *Many DNA fragments of diff lengths produced 3. DNA samples are mixed with loading dyes and staining agent 4. Gel is covered with buffer solution 5. DNA fragments are loaded into wells at the negative end of the gel (cathode) *DNA ladder with DNA fragements of known length is usually run through the gel at the same time 6. A direct current is applied through the gel 7. DNA is attracted towards the positive electrode (anode) *Separation due to electric field/potential dfference *Bcs DNA is negatively charged due to phosphate groups *Gels acts a molecular seive *Shorter fragments of DNA move faster and further per unit time through the gel than larger fragements *Due to less impendance of gel *DNA fragements seperate and arranged in order of size 8. Visualise bands under UV light *Staining agent causes DN to fluoresce *Each band is millions of DNA pieces of the same size *Compare position with reference DNA to estimate length of fragements 9. DNA pieces transferred to membrane/nylon/nitrocellulose/absorbent paper *This is called southern blotting 10. DNA heated to separate strands 11. DNA cooled and gene probes are added *Gene probes are used to locate a specific DNA sequence or gene *Gene probes=short, single stranded DNA (ssDNA) *"Labelled"/attached with radioactive/fluorescent substance *Can complementary base pair with specific DNA fragments 12. View DNA fragments under UV light/x-ray film

Answer 9

1. Extract DNA from tissue samples(e.g. blood, hair root, semen, saliva) 2. Identity up to 13 VNTR regions *Variable number of tandem repeats =short lengths of repetitive, non-coding sections of DNA *Each induvidual has two allels for each VNTR *Number of repeats differ between induviduals *One from each homologous chromosome (from parents) 3. Quantity of DNA increased by polymerase chain reaction (PCR) 4. DNA fragmented by restriction enzymes 5. Gel electrophoresis of DNA→DNA pieces transferred to membrane →heated to seperate strands→gene probe added →Visualise under UV light/X-ray film→banding pattern seen

Answer 10

Applications: *Used to find relatedness with other individuals *paternity testing →Usually mother is known →Child inherits one allele from mum, one from dad *Criminal identification in forensics

Answer 11

*Aka genetic testing *Analysis of a person’s DNA to check for presence of a particular allele *DNA obtained from tissue samples (e.g. blood) *Can be carried out on embryo, fetid, newborn or adults *Important examples: breast cancer, haemophilia, sickle cell anemia, Huntington’s disease, cystic fibrosis (CF), down syndrome

Answer 12

1. Pre-implantation genetic diagnosis (PGD): Newly formed embryo from IVF, before implantation into uterus of mother. 2. Prenatal screening: Unborn children/ fetus 3.Newborn screening: New born babies 4. Carrier screening: Individuals with a family history of a genetic condition/cancer and potential parents

Answer 13

*Newly formed embryo from in vitro fertilisation (IVF) *Tested before implamantation into uterus of mother Procedure: 1)Embryo biopsy=removing a cell from an embryo *At 8-cell stage (day 4/5) 2)PCR to amplify DNA 3)Gel electrophoresis *Analyse DNA for faulty alleles to determine if embryo has genetic disease *E.g. haemophilla huntingdon's disease, cystic fibrosis 4)Pre-selection=select only embryo without faulty alleles for implantation

Answer 14

Social or ethical implications: *Identify whether embryos from IVF have a genetic condition →Avoid implantation of embryos with faulty alleles →Allows couples to have children who would otherwise choose not to But its controversial: Ethical concerns: *Embryos might be destroyed if not pre-selected for implantation *Could leas to selection based on gender or specific traits (designer babies) *Contrary to beliefs/values *Genetic disease may not develop

Answer 15

1) Amniocentesis:Needle used to withdraw foetal cells from amnitioc fluid 2) Chorionic villus sampling (CVS)-Sunction tube used to remove foetal cells from chorion (where plancenta will develop)

Answer 16

Advantages: *Helps to provide early diagnosis for fetuses in utero →So can give early treatment when born →Allow parents to prepare for the birth of a child who will need treatment for a considerable time or even throughout life →Women can avoid late therapeutic abortions=terminate pregnancy for medical reasons

Answer 17

E.g. haemophilla, sickle cell anaemia, cystic fibrosis, huntingdon's disease down syndrome E.g. breast cancer *Faulty alleles of BRAC1 and BRAC2 genes *Increase the chance of developing breast cancer *High risk If tested positive for the faulty alleles: *Increased testing to detect cancer early *Elective mastectomy=removal of breast(s) before the occurrence/diagnosis of cancer

Answer 18

Advantages: *Can identify carriers of genetic conditions →Allow couples who are both carriers of a genetic condition to choose not to have children *Helps to provide early diagnosis e.g. Huntington's disease (symptoms only occur later in life) →Can prepare for the future: 1. If present, enables lifestyle change/early treatment/regular check-ups 2. Prevantative treatment may be cheaper than treating disease itself →If tested negative, genetic screening removes anxiety

Answer 19

Disadvantages: *Test is expensive *Many mutations still unknown so may still not lead to positive diagnosis If person tested positive: *For some diseases, no treatment is possible *May lead to anxiety *may experience social/financial discrimination (e.g. life insurance refusal) *May still not develop diseases even though mutation is present *Couple may decide to not hve children OR couple may be tested after they have children

Answer 20

Couples are referred to genetic counsellors if they: *Both have genetic disease in family or are carrier *have history of recurrent miscarriages *female is an older woman Genetic conseller can: *Run pedigree analysis + genetic screening *Explain results of tests / estimate chances of having affected child Genetic counsellor may discuss/advice on options: *termination or therapeutic abortion *therapies/treatments (e.g. gene therapy) *The effect of having child on existing siblings

Answer 21

*To treat serious, common genetic diseases *Caused by a single faulty, recessive allele *By inserting normal, dominant allele *Into affected cells of induvidual *Via a vector (e.g. virus, liposome or just naked DNA) *Result=host will have recombinant DNA Aim: To obtain functional normal polypeptide *Reduce symptoms of disorder *Restore/enhance cellular functions *Increase quality of life/survival e.g. SCID, cystic fibrosis, Leber's congenital amaurosis (LCA), thalassemia, haemophillia

Answer 22

If faulty allele was dominant, gene therapy is very very diffucult because... *It will still be expressed even when the normal, recessive allele is present *We'll need to knowck out/remove/replace the faulty allel →Extremely diffucult bcs it requires insertion of DNA into precise location in genome e.g. huntington's disease: *Caused by a faulty, autosomal dominant allele of the huntintin gene *Dominant allele also affects tissues in many parts of the body →Gene therapy only alters genotype of a few targeted cells

Answer 23

procedure: 1. Obtain normal, dominant allele/cDNA from mRNA in cells of healthy person 2. Use gel electrophoresis+gene probe for identification 3. Use PCR to amplify DNA 4. Make recombinant DNA *Use restriction enzyme to cut DNA and form complementary sticky ends *Use DNA ligase to join cDNA with promoter/vector DNA *Add human promoter upstream of targer allele to ensure transcription in host 5. Inset normal allele into vector *Virus vector/liposome vector/naked DNA 6. Inject/spray into host

Answer 24

1. Virus vector *Usually retroviruses *Non-pathogenic *Naturally inserts its viral DNA into host genome *Recognises specific cells Problems: *May cause side effects/allergies *May be removed by immune system before it reaches target cells *The virus may trigger an immune response which destroys the infected cells *Most non-pathogenic viruses are not very good at getting into cel, so very few cells receive the allele *Short term effect as host cells have short lifespan *Repeat treatments needed *Retroviruses also cause random insertion of genes into host's genome *May inset its genes with another gene or within regulatory sequence *May activate oncogenes/switch off tumore suppressor genes→cancer *May have uncontrolled viral replication Solution: *Adeno-associated virus (AAV) does not insert genes into hosy's genome, not passed on to daughter cells *Lentiviruses can be modified to have no uncontrolled viral replication *Or use different vector!

Answer 25

*Small sphere of phospholipid *Sprayed as an aerosol/delivered using inhaler *Liposome fuses with host cell surface membrane *Trigger the immune response less than viruses Problems: *Not as effective in insertion as viruses *Short term effect as host cells have short lifespan *Repeat treatments needed

Answer 26

*Very cheap *Can be delivered via direct injection or gene gun *No problems associated with using vectors *Does not trigger immune response Problems: *Easily degraded *Gene expression is very low

Answer 27

*Severe combined immunodeficiency (SCID) *Immune cells do not work properly *Highly susceptible to infections *B and T cells unable to make adenosine deaminase (ADA) *Due to faulty allele coding for the enzyme *X-linked recessive allele Gene therapy: 1. Remove T lymphocytes 2. Introduce normal allele for ADA enzyme using virus 3. Replace T-lymphocytes into body Problem: Regular transfusions of T cells are needed (not a permanent cure) Alternative, long lasting method: *Give a drug to increase number of stem cells in bone marrow *Remove stem cells from bone marrow *Insert normal alleles into stem cells using retroviruses *Radiotherapy to kill stem cells in bone marrow *Return stem cells into patient *Lymphocytes produce functioning ADA Problem: *Side effect=leukemia *Due to random insertion of alleles into cell's genome Solution: *Use Adeno-associated viruses (AAV)

Answer 28

*Leber's congenital amaurosis (LCA) *Autosomal recessive eye disease *Retina cells die off gradually *Severe loss of vision at birth *delivery of dominant, normal allele using adeno-associated virus (AAV) *Vectors are injected directly into the retina *So retina cells can make functional protein and restore vision Suitable for treatment using gene therap bcs: *Caused by recessive allele of a single gene *Only need to get allele into a few cells *Ease of access to affected area *Only targer eye/no surgery needed *Serious so worth the risk

Answer 29

*Inherited genetic disease *faulty, autosomal recessive allelle of the CFTR gene Normal CFTR protein: *Transmembrane protein at cell surface membrane *Acts as chloride channel *Has binding site for ATP *Cl- moves out of cell via active transport *Water is drawn out from cell →Normal/less viscous mucus formed →Easy removal by cillia Faulty CFTR allele: a)Base deletion→Faulty CFTR (most common) b) Base substition→STOP codon→Incomplete CFTR faulty CFTR protein: *No functional channels for Cl- ions *Cl- ions do not move out *Less water leaves cell →Formation of thick, sticky mucus on cell surface membrane →Cannot be removed by cilia

Answer 30

*Thick and sticky mucus produced at lungs *Mucus not moved effectively by cilia→mucus accumulates *Mucus traps bacteria→more infections *reduced gaseous exchange→due to longer diffusion pathway *Difficulty in breathing, wheezing *Coughing→cause lungs to be scarred *Blocked pancreatic duct→reduced digestion, damage of pancreatic tissues causes diabetes *Blocked sperm ducts/oviducts →reduced fertility

Answer 31

Traditional treatments: *Deals with symptoms only not causes 1. Thick mucus in lungs→physiotherapy, percussion therapy to loosen and remove the mucus easily 2. recurrent bacterial infections→antibiotics 3. Reduced digestion→Enzyme supplements Gene therapy: *Insert normal allele for CFTR into lung cells →usually inhaled or sprayed *treats the cause rather than the symptoms *no physiotherapy, antibiotics etc. needed *Less time consuming than other treatments *Effects are short-lived (few days) and treatmet needs repeating *May have side effects

Answer 32

Vectors commonly used: 1)Liposomes *Sprayed into nose *not long lasting and only a few cells received the normal allele 2)Adenoviruses *Normal harmless *Used to infect respiratory cells *Not all cells take up virus *Side effects due to viral infection

Answer 33

1) To distingush between allels of a gene *Use DNA microarray *Compare alleles found in genome of 2 induviduals/species 2)To identify expressed/transcribed genes *Transcription of a gene produces mRNA *So can assess gene expression by measuring mRNA levels *Compares relative mRNA levels between 2 samples *One acts as a control (normal cells)

Answer 34

Components: A microarray chip *Involves a "chip" wich has >10,000 cells *Gene probe is bound at known positions to a chip *Gene probe=short lengths of single-stranded DNA (ssDNA) complementary to allele/gene *Many copies of one type of probe placed in one cell of the microarray *Diff cells has a diff type of gene probe complementary to specific allele/gene *So many genes can be assessed at the same time!

Answer 35

1A. To distinguish between alleles of a gene Extract DNA from 2 samples *Cut into DNA fragments *Denature DNA into ssDNA by heating it OR 1B. To identify expressed/transribed genes isolate mRNA of cells of 2 samples *Use mRNA as a template to form single-stranded complementary DNA (cDNA) *use reverse transcriptase 2. Label ssDNA to hybridise/bind to the complementary gene probes 3. Labelled ssDNA from both samples are washed over microarray *Allow ssDNA to hybridise/bind to the complementary gene probes *Unbound ssDNA will be washed off *Bound DNA will not be washed off 4. Use laser/UV light to identify fluorescent spots *Fluorescence=hybridised probes with ssDNA=gene is expressed *Position and intensity is recorded by scanner →Positions are then identified as named genes *Intensity porportional to gene expression

Answer 36

Applications: *genetic screening-can distinguish between alleles of a gene *Drug testing-identify which genes the drugs have acted on *Identifiying genes that are overexpressed/ not expressed in diseases

Answer 37

*Interdisciplinary field *Collection, processing and analysis of biological information and data *Using computer programs/software *It is a store/database →Collection of huge-quantities of data ("big data") from all over the world →From DNA sequencing, microarrays, other techniques →Can search online for DNA and amino acid sequences →And use that to model/predict tertiary structure of protein Function: to allow comparison of DNA and protein sequences

Answer 38

*Determine the exact sequence of bases in genes *Fully automated process *Genomes of many species have been published *Gives information about the location of genes *Provides evidence for the evolutionary links between organisms

Answer 39

Applications: *Identify evolutionary relationships/genetic relatedness *By Comparing between genomes/protein sequence of diff species *Close similarities=recent common ancestry *Compare beween genes/proteins of humans and model organism *E.g. mouse, drosophila fruit flies, yeast, C. elegans roundworm *If target gene have similar sequence and protein have similar structure *Model organism can be used to investigate when and where genes have effect in humans *Identify genome sequence and proteins of pathogens *E.g. Plasmodium, straphylococcus areus *Can help in vaccine/drug development

Answer 40

Can use database to: *Identify genes *Predict amino acid sequences of proteins *Predict 3D structure of proteins *Identify functions of proteins from 3D structure Can formulate drug to: *Bind with protein/enzyme *Block activity of protein/enzyme *Distrupt structure of protein/enzyme *Prevent transcription of gene

Answer 41

To cut DNA at specific loci and allow genome editing

Answer 42

*Inexpensive, much easier and very effective *Bacterial system to protect itself agaisnt virus Components: *Cas9=enzymes that cut DNA *gRNA=guide RNA that is complementary to target DNA Result:A double-stranded break is introduced at specific loci *Cells will try to repair the double stranded break but repair is error prone *Extra bases are included→gene is disrupted and deactivated Potential: *Technology is versatile and improving →Can combine with other enzymes in order to introduce specific mutations/increase transcription/insert gene at specific location etc →Can combine with GFP and act like a gene probe in situ *Cure viral diseases and genetic diseases even cancer! →Can inject CRISPR into body →Extend life expectancy Potenital issues: *Increased preselectiom *Designer babies, supersoldiers and biological weapons

Genetic technology Flashcards

(66 cards)