Biology (2017) INTERNATIONAL GCSE. TOPIC GUIDE: Genetic modification and cloning. Pearson Edexcel International GCSE in Science

Transcription

1 INTERNATIONAL GCSE Bilgy (2017) TOPIC GUIDE: Genetic mdificatin and clning Pearsn Edexcel Internatinal GCSE in Science

2 Intrductin t the teaching f genetic mdificatin and clning Specificatin In the 2011 Edexcel Internatinal GCSE specificatin, the sectin cvering genetic mdificatin and clning is set ut in the fllwing way: Students will be assessed n their ability t: 5.12 describe the use f restrictin enzymes t cut DNA at specific sites and ligase enzymes t jin pieces f DNA tgether 5.13 describe hw plasmids and viruses can act as vectrs, which take up pieces f DNA, then insert this recmbinant DNA int ther cells 5.14 understand that large amunts f human insulin can be manufactured frm genetically mdified bacteria that are grwn in a fermenter 5.15 evaluate the ptential fr using genetically mdified plants t imprve fd prductin (illustrated by plants with imprved resistance t pests) 5.16 understand that the term transgenic means the transfer f genetic material frm ne species t a different species describe the prcess f micrprpagatin (tissue culture) in which small pieces f plants (explants) are grwn in vitr using nutrient media 5.18 understand hw micrprpagatin can be used t prduce cmmercial quantities f identical plants (clnes) with desirable characteristics 5.19 describe the stages in the prductin f clned mammals invlving the intrductin f a diplid nucleus frm a mature cell int an enucleated egg cell, illustrated by Dlly the sheep 5.20 evaluate the ptential fr using clned transgenic animals, fr example t prduce cmmercial quantities f human antibdies r rgans fr transplantatin.

3 In the revised 2017 Edexcel Internatinal GCSE specificatin, this sectin is set ut in the fllwing way: Students shuld: 5.12 understand hw restrictin enzymes are used t cut DNA at specific sites and ligase enzymes are used t jin pieces f DNA tgether 5.13 understand hw plasmids and viruses can act as vectrs, which take up pieces f DNA, and then insert this recmbinant DNA int ther cells 5.14 understand hw large amunts f human insulin can be manufactured frm genetically mdified bacteria that are grwn in a fermenter 5.15 understand hw genetically mdified plants can be used t imprve fd prductin 5.16 understand that the term transgenic means the transfer f genetic material frm ne species t a different species 5.17B describe the prcess f micrprpagatin (tissue culture) in which explants are grwn in vitr 5.18B understand hw micrprpagatin can be used t prduce cmmercial quantities f genetically identical plants with desirable characteristics 5.19B describe the stages in the prductin f clned mammals invlving the intrductin f a diplid nucleus frm a mature cell int an enucleated egg cell, illustrated by Dlly the sheep 5.20B understand hw clned transgenic animals can be used t prduce human prteins Summary f the changes 5.15 has been altered frm specifically expecting students t understand the reasns fr prducing pest resistant crps t a general idea f imprved fd prductin has been altered slightly the wrding is mre general as students are still expected t understand all the steps that are taken when carrying ut micrprpagatin has been altered t a mre general understanding that clned animals can be used t prduce a range f human prteins rather than human antibdies r transplant rgans. Students will still be expected t be familiar with a range f uses. Pints 5.17 and 5.20 are specific t Bilgy Internatinal GCSE and nt the Science (Duble Award) specificatin hence being in bld type and with a specificatin reference ending with a B.

4 Genetic engineering (genetic mdificatin) It is beynd the scpe f this guidance dcument t prvide the full details f hw genetic engineering is carried ut. Key elements that students need t understand: There is a lt f key vcabulary in this tpic that may be challenging fr students with English as a secnd language. Prducing a glssary f key terms can help students. The key terms include: vectr, plasmid, restrictin enzyme, ligase, sticky ends, recmbinant DNA and transgenic. Fr students wh find this challenging, this can be prvided as a sentence srting activity that the teacher can check. The terms shuld be revisited several times. It is imprtant that students understand the differences between the functins f restrictin enzymes and ligase, and hw genes are inserted int plasmid vectrs. Building craft mdels can help student understanding and gives a kinaesthetic apprach t the subject. Pipe cleaners f different clurs make useful circular plasmids and pieces f DNA which can be cut with scissrs (restrictin enzymes) and glued tgether with mdelling clay (ligase). If pipe cleaners are nt available, different clured string (r wl) can be used. Students are expected t knw that genetically-engineered bacteria have been created t prduce human insulin and that the bacteria are grwn in fermenters (link t specificatin reference 5.8). Other examples, such as the prductin f grwth hrmne, can be researched by students. Althugh nt stated n the specificatin, it imprves understanding if students appreciate the benefits f prducing insulin by using bacteria. Benefits include: lw price lwer dsage needed than using insulin frm animals fewer ethical bjectins than using insulin derived frm animals less risk f allergic reactin than using insulin derived frm animals. Students are expected t understand hw genetic engineering can be used t imprve fd prductin. There is n specific example stated in the specificatin but students shuld have an appreciatin f sme f the different pssibilities as they may be used as stimulus material. It is als useful in terms f develping transferable skills if students cnsider advantages and disadvantages f genetically-mdified crps, and sme f the measures put in place t prevent their spread in the wild. Students culd investigate ne r tw f the examples n the fllwing page:

5 Pest-resistant crps. Cttn, maize and sya make up the majrity f the pest-resistant crps that are currently used. If crps are made pestresistant, yields will increase, as less will be cnsumed by pests such as insects. In develping natins, where pest plagues can wipe ut large numbers f crps, they culd reduce the risk f fd shrtages. They pse a risk if they travel int the wild where they culd cause the death f nnpest rganisms, affecting fd chains and utcmpeting native plants. There may als be a risk that pests develp resistance t the pesticides. Herbicide-resistant crps. Sya beans and maize (alng with ther crps) have been genetically mdified t be resistant t herbicides. Remving weeds is very time-cnsuming and labur intensive. Herbicideresistant crps enable fields f crps t be sprayed with large quantities f herbicide t kill the weeds. The crp plants survive, have less cmpetitin and s have a higher yield (with reduced labur csts). There are reprts that the intense use f herbicides is leading t resistant superweeds and that there are negative effects n fd chains in areas arund crp fields. Envirnmentally-resistant crps. Crps which are resistant t drught, salt and frst are being develped. They culd help prvide increased fd in areas which were previusly unsuitable fr farming, helping reduce famine in develping natins. But they culd lead t lss f ecsystems fr sme species f plants r animals, as mre land is turned ver t farming. Altered nutritin. Crps with increased vitamin cntent, such as Glden rice, which has additinal vitamin A, are under develpment. Glden rice culd be used t treat vitamin A deficiency, a majr cause f eye disease and blindness in children in develping natins. Sya beans with healthier ratis f fatty acids are als being develped. Pharma crps. Crps that prduce medicine are being develped. There are crps that prduce antibdies, vaccines and ther therapeutic prteins. They wuld be a cheap surce f prtein drugs that are ften btained frm animals. This culd reduce the risk f the transfer f diseases frm animals t humans, and imprve animal welfare. Imprved crps. Crps with a lnger shelf life, higher yield and better flavur are all being cnsidered. A range f different types f these crps are under develpment. They are principally t satisfy cnsumer demand but culd als bring dwn fd prices. Genetically-mdified crps must underg stringent testing befre being used cmmercially. There must be n risk f pllen, seeds r plants escaping frm the fields. They are kept in high security areas where wind pllinatin and insect pllinatin cannt ccur until they are prven t pse n risk t the envirnment. Students culd hld a debate abut whether the use f genetically-mdified crps shuld be allwed. Data shuld be given t them t help supprt each side in the debate. There are many websites cvering bth sides f the debate care shuld be taken t ensure that they are reputable and prvide a balanced argument, fr example: Fr students wh find the tpic challenging, a card-srting exercise, with examples f genetic engineering alng with statements f uses and risks, can be used.

6 Plant micrprpagatin and animal clning It is beynd the scpe f this dcument t describe all the steps invlved in micrprpagatin and animal clning. Key elements that students need t understand are as fllws: All the stages in micrprpagatin f plants need t be cnsidered. There is a lt f key vcabulary and students, particularly thse with English as a secnd language, benefit frm prducing a glssary f terms (and relevance t micrprpagatin). Terms include: explant, clne, sterile, nutrient agar, grwth factrs, humidity, phtsynthesis. A similar glssary f terms can be used when teaching animal clning. Key terms include: enucleated egg cell, diplid nucleus, electric shck, mitsis, embry, surrgate mther, uterus. Students wh find the tpic f animal clning challenging can mdel the transfer f a nucleus frm the bdy cell f ne sheep int the empty egg frm a different sheep, and the transfer f the embry int the uterus f a third sheep. A kinaesthetic apprach ften helps students understand the transfer f genetic material. Bth micrprpagatin and animal clning ccur as a sequence f events. Card-srting exercises can be used. Students can be given cards with each f the key stages and then srt them int the crrect rder. This is particularly effective fr students wh find the tpic challenging. Cauliflwer plants can be clned this activity reinfrces the tpic n cell differentiatin and stem cells. Many prtcls are available, such as: If it is nt pssible t maintain sterile cnditins t carry ut cauliflwer clning, a simulatin can be carried ut using sterile agar blcks and any plant. Even thugh this may nt result in the prductin f clned plants, it helps student understanding t carry ut a simulatin f the techniques.

7 The new specificatin des nt give specific examples f uses f animal clning. Students shuld investigate tw r three different examples and understand that clning is ften used alngside genetic engineering. In particular, transgenic animals that are engineered t prduce human prteins can then be clned t make multiple genetically identical cpies. Examples f animal clning include: Dlly the sheep the first mammal t be clned using an adult nucleus. Cattle have been prduced that make human antibdies that can be used t treat infectins. Cattle have been prduced that make humanised milk. They were genetically engineered t release human prteins such as lyszyme enzyme int their milk. Sheep that prduce human-alpha-1-antitrypsin in their milk have been created. This prtein is used t treat a lung disease called hereditary emphysema. Pigs have been genetically engineered with human antigens n their cells. These animals culd be used fr transplant rgans that wuld nt be rejected by the human immune system. There are pprtunities fr extensin with this tpic. Students culd investigate ther ptential uses f clning, such as making cryzs t preserve cells frm endangered species, making genetically-mdified fd rganisms e.g. AquAdvantage salmn, and the clning f pet cats and dgs. Students culd als debate the values and risks f clning. The fllwing vide culd lead a discussin abut whether a clned pet wuld have the same behaviurs and temperament as the riginal pet: The ptential fr human clning culd be investigated and linked t statement 2.6B abut the uses f stem cells in medicine. Ethical issues can be studied as part f this tpic. The effects f plant mnculture culd be debated, such as the effect f Panama fungus n banana plants. Aspects f animal clning, such as animal welfare issues and the lw efficiency f the prcess can als be cnsidered. A nte fr teachers Nte that this Guide is intended t supprt teachers f Internatinal GCSE Bilgy and prvides subject cverage beynd the demands f the specificatin.