Topic 8 Flashcards

Question

What are the benefits of stem cell therapy?

Answer 1

* could save many lives e.g. many people waiting for organ transplants die before a donor organ becomes available, so stem cells could be used to grow organs for those awaiting transplants * may be possible to make stem cells genetically identical to a patient's own cells, which could be used to grow some new tissue or an organ that wont be rejected by patient's body * could improve the quality of life for many people e.g. they could be used to replace damaged cells in the eyes of blind people

Answer 2

* in eukaryotes, transcription of target genes can be stimulated or inhibited when specific transcriptional factors move from the cytoplasm into the nucleus * this can turn on/off genes (only certain genes can go through protein synthesis to make a particular protein), so only certain proteins are produced in a particular cell * turning on/off particular genes in a cell is what enables them to become specialised

Answer 3

* Genes are regulated by transcription factors * Transcription will only occur when a transcription factor from the cytoplasm enters the nucleus and binds to the DNA in the nucleus * transcription factors are proteins and each one can bind to different base sequences on DNA, which they are complementary in shape to, which enables RNA ploymerase to bind, and so transcription factors initiate transcription of genes * Transcription factors are three dimensional proteins. One part binds to DNA and another part of protein often a receptor for another molecule to attach to before it can then attach to DNA * once bound, transcription begins, creating mRNA molecule for that gene which can then be translated in the cytoplasm to create the polypeptide chain/protein * without the binding of a transcription factor, the gene is inactive and the protein will not be made

Answer 4

* oestrogen is a **steroid hormone** that can initiate transcription. * lipid soluble as is a steroid hormone so can enter cell through cell surface membrane via simple diffusion * it binds to the transcription factor (called an oestrogen receptor) by the receptor site, as oestrogen is complementary in shape to the receptor site. This forms an oestrogen-oestrogen receptor complex * when it binds to transcription factor it causes the DNA binding site of the protein to change shape slightly, so it is complementary in shape to DNA. * The transcription factor is now activated * The transcription factor/ oestrogen-oestrogen receptor complex can move through nuclear pores into the nucleus and bind to specific DNA sites near start of target gene. Complex acts as an activator of transcription by helping RNA polymerase bind to start of target gene. * RNA polymerase can then bind to DNA/start of target gene to create mRNA (transcription factor binding to DNA initiates transcription, as RNA polymerase can only bind to DNA once transcription factor is bound as RNA polymerase is only complementary in shape to DNA and transcription factor together)

Answer 5

* genes are regulated by transcription factors * all cells in an organism carry the same DNA but the structure and function of different cells varies because not all the genes in a cell are expressed (transcribed and used to make a protein) * as different genes are expressed, different proteins are made and these proteins modify the cell, so determine the cell structure and control cell processes such as the expression of more genes, which produce more proteins

Answer 6

* in eukaryotes transcription factors move from the cytoplasm to the nucleus * they bind to specific DNA sites called **promoters** which are found near the start of their target genes (the genes the transcription factors control the expression of). Transcription factors control gene expression by controlling rate of transcription * transcription factors called **activators** stimulate/increase rate of transcription e.g. help RNA polymerase bind to the start of the target gene and activate transcription * transcription factors called **repressors** inhibit/decrease rate of transcription e.g. they bind to the start of the target gene, preventing RNA polymerase from binding, stopping transcription

Answer 7

epigenetics * epigenetics is the heritable change in gene function without changing the DNA base sequence * changes caused by changes in the environment and can inhibit transcription * factors such as diet, stress and toxins can add epigenetic marks (chemical tags) to the DNA and this can control gene expression in eukaryotes. * epigenetic marks do not alter base sequence of DNA. They alter how easy it is for the enzymes and other proteins needed for transcription to interact with and transcribe DNA * epigenome= single layer of epigenetic marks on DNA, which impacts the shape of the DNA-histone complex and whether the DNA is tightly woud so wont be expressed or unwound wo will be expressed * if DNA tightly wound, transcription factors cannot bind, SO the epigenome, which is due to changes to the environment, can inhibit transcription

Answer 8

* when methyl groups (e.g. of an epigenetic mark) are added to DNA they attach to the cytosine base * this prevents transcriptional factors from binding and attracts proteins that condense the DNA-histone complex, so methylation prevents a section of DNA from being transcribed. * Methylation of DNA and histones causes changes to the DNA structure and causes DNA to coil tightly so transcriptional factors cannot bind the DNA and genes are not expressed (switched off)

Answer 9

* histones are proteins that DNA wraps around to form chromatin that makes up chromosomes. How condensed chromatin is affects the accessibility of DNA and whether or not it can be transcribed. * acetyl groups are e.g. of epigenetic marks * decreased acetylation of associated histones proteins on DNA inhibits transcription * if acetyl groups removed from DNA the histones become more positive and are attracted more to the phosphate group on DNA * this makes DNA and histones more strongly associated and hard for transcription factors to bind. * when acetyl groups removed from the histones, the chromatin becomes highly condensed and genes in DNA cannot be transcribed because transcription factors cannot access them * when histones are acetylated, the chromatin is less condensed so transcription factors can access DNA so genes are transcribed * Histone deacetylase enzymes (HDAC) remove acetyl groups

Answer 10

* transcription cannot occur * caused by increased methylation of DNA that inhibits transcription * caused by decreased acetylation of associated histones proteins on DNA that inhibits transcription

Answer 11

* transcription can occur * caused by decreased methylation * caused by increased acetylation of associated histones proteins

Answer 12

* damaging the organ in which the tumour is located * causing blockages or obstructions * damaging other organs by exerting pressure

Answer 13

cancerous tumours

Answer 14

* by growing rapidly, then invading and destroying surrounding tissues * cells within malignant tumours secret chemicals that cause the formation of blood vessels to supply the tumour with nutrients, growth factors and oxygen * cells can break off tumours and spread to other parts of body through bloodstream or lymphatic system **(Metastasis)** * Metastasis causes the spread of tumours to other places in the body, affecting multiplt organs * when removed with surgery, malignant tumours can still grow back * **carcinogens** can initiate the formation of malignant tumours * carcinogens may include UV or X ray exposure, Tobacco, asbestos, processed meat

Answer 15

an agent with the capacity to cause cancer in humans. If the agent causes cancer, it is carcinogenic

Answer 16

* non cancerous tumours * grow slowly * do not invade other tissues and no not metastasise, unlike malignant tumours * often covered in fibrous tissue that stops cells invading other tissues

Answer 17

* can cause blockages or obstructions * can exert pressure on the organ it is growing in or those surrounding it * when removed they do not usually grow back * formation of benign tumours initiated by inflammation or infection, injury, diet, genetics, toxins and radiation * some benign tumours can become malignant * examples of benign tumours include non cancerous brain tumours and warts, caused by a viral infection

Answer 18

* Tumour Suppressor genes are genes that produce proteins that slow down cell division, repair DNA, signal Apoptosis (cell death) when the cells are faulty * the proteins ensure that cells do not replicate if they contain mutated DNA or are faulty as that can lead to tumour formation * tumours occur if tumour suppressor genes are mutated or silenced * if mutations result in the tumour suppressor genes not producing these proteins that slow down cell division then cell division could continue and mutated cells would not be identified and destroyed. BRCA1 and BRCA2 are two known mutated tumour suppressor genes linked to breast cancer

Answer 19

* Methylation of DNA is important method of regulating gene expression as it can control whether or not a gene is transcribed and translated * when occurring normally it plays a key role in many bodily processes * growth of tumours can be caused by abnormal methylation of certain cancer-related genes * Tumour suppressor genes could become hypermethylated (too many methyl groups are attached to it), so the genes are not trancribed. The gene is inactivated and becomes turned off * the necessary regulatory proteins produced by the tumour suppressor gene (for slowing cell division, DNA repair and apoptosis) are not produced, so this could result in a tumour, as cells can divide uncontrollably by mitosis. * proto-oncogenes may be hypomethylated (reduction in number of methyl groups attached to cytosine base), which causes them to act as oncogenes, increasing the production of proteins that encourage cell division. * This stimulates cells to divide uncontrollably, which causes the formation of tumours. * hypomethylation of proto-oncogenes causing them to act as oncogenes results in the gene being permanently switched on.

Answer 20

* Proto-oncogenes are normal genes that stimulate cell division by coding for proteins that make cells divide * Proto-oncogenes can mutate to become oncogenes * mutation occurs because of carcinogens such as smoking etc * Oncogenes are mutated genes that can cause cancer through deregulation of cell growth * mutations to proto-oncogene can cause the gene to become overactive which stimulates cells to divide uncontrollably, resulting in a tumour

Answer 21

* oestrogen is a steroid hormone that can initiate transcription of certain genes * increased exposure to oestrogen over an extended period of time is thought to increase the risk of developing breast cancer (can be the result of starting menstruation earlier than usual or the menopause later thsn usual or taking oestrogen containing drugs such as HRT) * different theories as to how oestrogen can contribute to the development of some breast cancers: 1. oestrogen can stimulate certain breast cells to divide and replicate, so increased cell division increases chance of mutations occurring so increases chance of cells becoming cancerous 2. ability to stimulate cell division could mean that if cells become cancerous then oestrogen could cause them to rapidly divide further so tumours form faster 3. other research suggests oestrogen is able to introduce mutations directly into the DNA of certain breast cells, increasing the chance of these cells becoming cancerous

Answer 22

* RNAi can inhibit the translation of the mRNA produced from target genes in eukaryotes and some prokaryotes * RNAi is where small double stranded RNA molecules stop mRNA from target genes being translated into proteins * molecules involved in RNAi are siRNA (small interfering RNA) and miRNA (micro RNA) * RNAi molecules are small lengths of non coding RNA

Answer 23

1.Transcribed mRNA leaves the nucleus of the cell to go to cytoplasm 2. in cytoplasm, double stranded siRNA associates with several proteins and unwinds. A single strand then binds to the target mRNA. Base sequence of siRNA is complementary to the base sequence in sections of target mRNA 3. proteins associated with siRNA cut mRNA into fragments, so it can no longer be translated. Fragments then move into a processing body, where they are degraded 4. similar process happens with miRNA in plants

Answer 24

1. in mammals, miRNA is not usually fully complementary to target mRNA, which makes it less specific than siRNA, so it may target more than one mRNA molecule 2. miRNA associates with proteins and binds to target mRNA in cytoplasm 3. mRNA then moves into a processing body where it is either stored or degraded. When it's stored, it can be returned and translated at another time.

Answer 25

The genome is the entire genetic material of an organism in the nucleus of a cell (in eukaryotes)

Answer 26

sequencing a genome means working out the DNA base sequence for all the DNA in a cell. All the cells have the same DNA (except gametes as they are haploid and red blood cells because they do not have a nucleus). Many organisms genomes have been sequenced, including the human genome which took 13 years and was completed in 2003.

Answer 27

* the methods being ued to sequence genomes are continuously being improved and updated and has now become automated * methods have included the Sanger method

Answer 28

* simpler organisms, like prokaryotic cells (bacteria) do not contain introns in their DNA * this means the genome can be used directly to sequence the proteins that derive from the genetic code (the proteome) of the organism * this is very useful for many reasons, including identifying potential antigens to use in a vaccine

Answer 29

* complex organisms (eukaryotes) have introns (non coding DNA) and regulatory genes in their DNA * this means that knowledge of the genome cannot easily be translated into the proteome.

Answer 30

* The combining of different organisms' DNA, which could enable scientists to mnipulate and alter genes to improve indstrial processes and medical treatment * recombinant DNA technology involved transferring a fragment of DNA from one organism to another * as the genetic code is universal, (the same DNA base triplets code for the same amino acids in all living things, and because the mechanisms of transcription and translation are universal, the transferred DNA can be translated to produce a protein in the cells of the recipient organism. * the first step in this technology is to produce or isolate the fragments of DNA to be recombined with another piece of DNA * There are 3 methods to create fragments of DNA: reverse transcriptase, restriction endonuclease enzymes and using a 'gene machine'

Answer 31

1. Reverse Transcription enzyme makes DNA copies from mRNA, (as most cells only contain 2 copies of each gene so it's difficult to obtain a DNA fragments with the target gene BUT they contain many mRNA molecules complementary to the target gene, so mRNA can be used as a template to produce DNA). Reverse Transcription naturally occurs in viruses such as HIV 2. A cell that naturally produces the protein of interest is selected 3. These cells should have large amounts of mRNA that are complementary to the target gene, so the protein can be made. The mRNA molecules can be used as templates to make lots of DNA 4. The reverse transcriptase enzyme joins the free DNA nucleotides that has complementary bases to the mRNA sequence 5. single stranded DNA is made (cDNA) 6. to make this DNA fragment double stranded, the enzyme DNA polymerase is used

Answer 32

* pancreatic cells produce the protein insulin * have many mRNA molecules complementary to insulin gene but only 2 copies of the gene itself * reverse transcriptase could be used to to make cDNA from the insulin mRNA * mRNA is first isolated from cells * mRNA is mixed with free DNA nucleiotides (that have complentary bases to the mRNA sequence) and reverse transcriptase * reverse transcriptase uses mRNA as a template to synthesise a new strand of cDNA

Answer 33

* the cDNA is intron free because it is based on the mRNA template * This is important if carrying out genetic engineering on prokaryotic cells as they cannot remove introns through splicing * secondly, mRNA present in cell is from actively transcribed genes, so lots of the mRNA of interest available to make cDNA

Answer 34

1. some sections of DNA have palindromic sequences of nucleotides, which consist of antiparallel base pairs (read the same in opposite directions) 2. restriction endonucleases recognise specific palindromic sequences (known as recognition sequences) and cut the DNA at these places 3. different restriction endonucleases cut at different specific reognition sequences because the shape of the recognition sequence is complementary to enzyme active site 4. if recognition sequences present at either side of the DNA fragment you want, restriction endonucleases can be used to separate it from the rest of the DNA 5. The DNA sample is incubated with specific restriction endonuclease which cuts the DNA fragment out via a hydrolysis reaction 6. some endonucleases cut the DNA to leave sticky ends (small sections of unpaired bases at each end of the DNA fragment). Sticky ends can be used to bind (anneal) the DNA fragment to another piece of DNA that has sticky ends with complementary sequences.

Answer 35

* enzymes that cut up DNA * naturally occur in bateria as a defence mechanism * many restriction enzymes that have an active site complementary in shape to a range of different DNA base sequences, decsribed as recognition sequences (the specific location each enzyme cuts the DNA from) * some enzymes cut at the same location in the double strand and create a blunt end * other enzymes cut to create staggered ends and exposed DNA bases. * exposed staggered ends are palindromic and referred to as 'sticky ends' because they have the ability to join to DNA with complementary base pairs. This is why these enzymes are the most useful * enzymes cutting DNA to create staggered ends and exposed DNA bases is an advantage as sticky ends provide larger SA

Answer 36

* most modern technology * DNA fragments can be created in a lab using a computerised machine * scientists first examine the protein of interest to identify the amino acid sequence (primary structure of protein) and from that work out what the mRNA sequences that coded for the amino acids and, from that, DNA sequence can be worked out * The DNA sequence is entered into the computer which checks for biosafety and biosecurity that the DNA being created is safe and ethical to produce * The computer can create small sections of overlapping single strands of nucleotides that make up the genes (called **oligonucleotides**) (oligo=small sections) * oligonucleotides can then be joined to create the DNA for the entire gene * PCR can be used to amplify the quantity and to make the double strand * This process is very quick, accurate (as exact desired sequence is designed and entered, so can be designed to be intron free and to have sticky ends) and makes intron free DNA so can be transcribed in prokaryotic cells

Answer 37

more steps, so more time consuming and technically more difficult

Answer 38

sticky ends on DNA fragment which make it easier to insert to make recombinant DNA

Answer 39

still contains introns, as cutting the original DNA - would be an issue if inserting DNA into a prokaryotic cell, as prokaryotic cells cannot remove introns through splicing, so an extra step would need to take place to remove introns before the DNA is inserted into prokaryotic cells

Answer 40

can design exact DNA fragment you want, with sticky ends, labels and preffered codons

Answer 41

need to know the exact sequence of amino acids or bases

Answer 42

1. DNA fragment isolated via one of 3 methods: Extraction using restriction endonucleases, the conversion of mRNA to cDNA using reverse transcriptase or artificial synthesis in a "gene machine". 2. **Promoter region** added at start of DNA fragment (sequence of DNA that is the binding site for RNA polymerase to enable transcription to occur). **Terminator region** added at end of gene, which causes RNA polymerase to detach and stop transcription so only one gene at a time is copied into mRNA * DNA fragment inserted into a vector (carries isolated DNA fragment into host cell). Most common vectors are plasmids (circular DNA, separate from main bacterial genome which only contains a few genes) * Vector DNA cut open using same restriction endonuclease used to isolate DNA fragment containing the target gene. Sticky ends of vector complementary to sticky ends of DNA fragment containing the gene * vector DNA and DNA fragment combined together with DNA ligase enzyme, which joins sticky ends of DNA fragment to sticky ends of vector DNA (anneals them). Process called**ligation**. Ligase catalyses the condensation reaction to form phosphodiester bonds between nucleotides * This forms **recombinant DNA** 3. vector with recombinant DNA used to transfer gene into host cell, where gene is expressed to create protein required * to do this, cell membrane of host cell must be more permeable. * Host cells mixed with ice cold calcium chloride solution to make cell walls more permeable, splamids added and mixture is heat shocked (sudden increase in temp) * enables vector to enter host cell cytoplasm * host cell has now been **transformed** by vector containing the gene, as host cell has taken it up. 4.

Answer 43

* not all host cells will take up a recombinant vector, so important to be able to identify which cells have been transformed. This can be due to the recombinant plasmid does not get inside the host cell, the plasmid re joins before the DNA fragment entered, or the DNA fragment sticks to itself, rather than inserting into the plasmid * marker genes can be used to identify transformed cells 1. marker genes can be inserted into vectors at the same time as the gene to be clones, meaning any transformed host cells will contain the gene to be clones and the marker gene 2. host cells grown on agar plates. Each plate divides and replicates DNA, creating a colony of clones cells. Transformed cells produce colonies where all cells contain clones gene and marker gene 3. marker gene can code for antibiotic resistance, so host cells grown on agar plates containing the specific antibiotic so only transformed cells with the marker gene will survive and grow 4. marker gene can code for fluorescence, where agar plate placed under UV light and only transformed cells will fluoresce 5. markers can be enzymes. The enzyme lactase can turn a certain substance blue from colourless. Gene for this enzyme inserted into plasmid. The DNA fragment inserted in the middle of this gene to disrupt it. The bacteria are then grown on an agar plate with the colourless substance. The colonies which cannot turn the colourless substance blue contain the recombinant plasmid. 5. identified transformed cells are allowed to grow more, producing many copies of the cloned gene

Answer 44

* a fermenter is used to grow multiple copies of the host cell which have been identified as containing the recombinant plasmid (transformed host cell) * large clones population of host cell can then produce the protein coded for by the inserted DNA fragment (e.g. bacteria producing insulin from an inserted insulin gene)

Answer 45

* ONce DNA fragments isolated, they are cloned to create large quantities. This is done either in vivo or in vitro * DNA fragments amplified using **in vitro** cloning, where copies of the DNA fragments made **outside**of a living organism using the polymerase chain reaction (PCR) 1. Reaction mixture set up containing DNA fragment, free nucleotides, primers and DNA polymerase. Primers are short pieces of DNA that are complementary to the bases at the start of the DNA fragment. DNA polymerase creates new DNA strands 2. DNA mixture heated to 95*C to break the hydrogen bonds between the two DNA strands. **(DNA is denatured)** 3. mixture then decreased to 55*C so that primers can bind **(anneal)** to the strands 4. reaction mixture heated to 72*C which is the optimum for DNA polymerase to work 5. DNA polymerase lines up free DNA nucleotides alongside each template strand and joins nucleotides together. Specific base pairing means new complementary strands formed. **(synthesis)** 6. two new copies of the DNA fragment formed and one cycle of PCR complete. Cycle starts again and all 4 strands (two original and two new) used as templates 7. each PCR cycle doubles the amount of DNA e.g. 1st cycle = 2 x 2= 4 fragments, 2nd cycle = 4 x 2= 8 fragments

Answer 46

* automated- more efficient * rapid- 100 billion copies of DNA can be made within hours * does not require living cells- quicker and less complex techniques needed compared to in vivo cloning

Answer 47

* microorganisms, plants and animals can all be transformed using recombinant DNA technology (this is called genetic engineering) * transformed microorganisms (aka genetically engineered/genetically modified (GM) organisms) can be made using same technology as in vivo cloning. DNA fragment isolated and is inserted into plasmid vector. Plasmid containing recombinant DNA tranferred into a bacterium. Tranformed bacteria identified and grown. The insulin (protein) produced from cloned gene is extracted and purified. * transformed plants can be produced. A gene that codes for a desirable protein inserted into a plasmid. Plasmid added to bacterium and bacterium used as a vector to get the gene into the plant cells. If correct promoter region has been added along with the gene, the transformed cells will be able to produce the protein * transformed animals can be produced. Gene that codes for desired protein inserted into early animal embryo/ egg cells of female. If gene inserted into a very early embryo, all the body cells of the resulting transformed animal will contain the gene. Inserting it into egg cells means when female reproduces, all the cells of offspring will contain gene * promoter regions that are only activated in specific cell types can be used to control exactly which of an animal's body cells the protein is produced in. If the protein is only produced in certain cells, it can be harvested more easily. Producing the protein in the wrong cells could damage the organism.

Answer 48

* algricultural crops can be transformed so they give higher yields or are more nutritious SO these plants can be used to reduce the risk of famine and malnutrition. * crops can be transformed to have pest resistance so fewer pesticides needed, which reduces costs and reduces any environmental problems associated with using pesticides * for examples, golden rice is a variety of transformed rice containing one gene from a maize plant and one gene from a soil bacterium, which together, enable the rice to produce **beta carotene**. This is used by our bodies to produce **vitamin A** * golden rice being developed to reduce vitamin A deficiency in areas where there is a shortage of dietary Vitamin A, which can cause problems such as blindness

Answer 49

* industrial processes often use biological catalysts. These enzymes can be produced from transformed organisms, so they can be produced in large quantities for less money, reducing costs * e.g. Chymosin (or rennin) is an enzyme used in cheese-making, which used to be made from rennet (sybstance produced in the stomach of cows), but it can now be produced by trasnformed organisms * this means it can be made in large quantities, relatively cheaply and without killing any cows, making some cheese suitable for vegetarians

Answer 50

* many drugs and vaccines produced by transformed organisms * they can be made quickly, cheaply and in large quantities using recombinant DNA technology * e.g. insulin used to treat Type I diabetes and used to come from animals (cow, horse or pig pancreases). * This was not human insulin so it did not work quite as well * human insulin now made from transformed microorganisms, using a cloned insulin gene

Answer 51

1. * farmers may plant only one type of transformed crop **(monoculture)** * this may make the whole crop vulnerable to the same disease because the plants are **genetically identical** . Environmentalists also concerned about monocultures reducing biodiversity, as this could damage the environment 2. * some people are concerned about the possibility of **'superweeds'**(weeds that are resistant to herbicides. * These could occur if transformed crops interbreed with wild plants * There could then be an uncontrolled spread of Recombinant DNA, with unknown consequences 3. Organic farmers can have their crops **contaminated** by wind-blown seeds from nearby genetically modified crops. This means they cannot sell their crop as organic and may lose their income

Answer 52

* antiglobalisation activists oppose globalisation (e.g. the growth of large multinational companies at the expense of smaller ones). A few, large biotechnology companies control some forms of genetic engineering. As the use of this technology increases, these companies get bigger and more powerful. This may force smaller companies out of business e.g. by making it harder for them to compete * without proper labelling, some pople think they will not have a choice about whether to consume food made using genetically engineered organisms, which is an ethical issue * some consumer markets, such as the EU, wont import GM foods and products, which can cause an economic loss to producers who have traditionally sold to those markets.

Answer 53

* companies who own genetic engineering technologies may limit the use of technologies that could be life saving * some people worry this technology could be used unethically e.g. to make designer babies (babies that have characteristics chosen by their parents). This is currently illegal though.

Answer 54

* some debate about who owns genetic material from humans once it has been removed from the body (the donor or the researcher). Some argue the individual donor holds the right to their own genetic information, but others argue that value is created by the researcher who uses it to develop a medicine or in diagnosis * a small number of corporations own patents to particular seeds. They can charge high prices, sometimes including a 'technology fee', and can require farmers to repurchase seeds each year. If non-GM crops are contaminated by GM crops, farmers can be sued for breaching the patent law.

Answer 55

1. Agricultural crops could be produced that help reduce the risk of famine and malnutrition e.g. droight resistant crops for drought prone areas 2. Transformed crops could be used to produce useful pharmaceutical products e.g. vaccines, which could make drugs availabke to more people, e.g. in areas where refrigeration (usually needed for storing vaccines) is not available 3. medicines could be produced more cheaply, so more people can afford them 4. recombinant DNA technology has the potential to be used in gene therapy to treat human diseases

Answer 56

1. gene therapy involves altering the defective genes (mutated alleles) inside cells to treat medical disorders and cancer. The way this is done depends on whether the disorder is caused by a mutated **dominant allele** or **two mutated recessive alleles** 2. if caused by 2 mutated recessive alleles then a working dominant allele can be added to make up for them ('supplemet' the faulty alleles) 3. if caused by a mutated dominant allele, the dominant allele can be **silenced** (e.g. by inserting a DNA fragment in the middle of the allele so it does not work anymore) 4. Both these processes involve inserting a DNA fragment into the orginal DNA

Answer 57

1. The allele is inserted into cells using vectors just like in recombinant DNA technology 2. different vectors can be used e.g. altered viruses, plasmids or liposomes (spheres made of lipid)

Answer 58

1. **Somatic therapy:** involves altering the alleles in body cells, particularly cells most affected by the disorder. E.g. Cystic Fibrosis (CF) is a genetic disorder that is very damaging to the respiratory system, so somatic therapy for CF targets the epithelial cells lining the lungs. Somatic therapy does not affect the individual's sex cells/gametes (sperm or eggs), so any offspring may still inherit disease 2. **Germ line therapy:** involves altering the alleles in the sex cells. This means that every cell of any offspring produced from these cells will be affected by the gene therapy and they won't suffer from the disease. Germ line therapy in humans is currently illegal.

Answer 59

* some people are worried the technology could be used in ways other than for medical treatment, such as for treating the cosmetic effects of aging * other people worry there is the potential to do more harm than good by using the technology (e.g. risk of overexpression of genes- gene produces too much of the missing protein)