2B1 You and your genes    Guidance AB1.1.1 Inheritance traffic lightsTeaching notesThis activity is designed to review KS3...
B1 You and your genes    Guidance AB1.1.3 VariationTeaching notesThis activity reinforces students’ understanding of      ...
B1 You and your genesGuidance AB1.1.3 Variation                        © University of York (UYSEG) and              This ...
B1 You and your genesGuidance AB1.1.3 Variation                        © University of York (UYSEG) and              This ...
B1 You and your genes    Guidance AB1.2.1 Cloning plantsCloning cauliflower                                               ...
B1 You and your genes Guidance AB1.2.1 Cloning plantsAnswers to questions11 To kill any microorganisms on the surface of t...
B1 You and your genes    Guidance AB1.2.2 Twin studiesTeaching notesAs students work through this activity they practise  ...
B1 You and your genes    Guidance AB1.3.1 Inheriting genesTeaching notesThe animation (IB1.3.6) is designed for students t...
B1 You and your genes    Guidance AB1.4.1 Male or female?Teaching notesThe activity illustrates the random nature of      ...
B1 You and your genes    Guidance AB1.4.2 Inheriting sexTeaching notesThe animation is designed for students to work      ...
B1 You and your genes Guidance AB1.4.3 Caster Semenya’s storyTeaching notesThis activity provides students with an opportu...
B1 You and your genes    Guidance AB1.4.4 Looking at sets of chromosomesTeaching notesThis is an extension activity.      ...
B1 You and your genes    Guidance AB1.5.1 AllelesTeaching notesThe animation (IB1.5.4) is designed for students to        ...
B1 You and your genes    Guidance AB1.5.2 Modelling fertilisationTeaching notesThese activities are designed to clarify th...
B1 You and your genes Guidance AB1.5.2 Modelling fertilisationUsing beads to show how different allelescan be inheritedPea...
B1 You and your genes Guidance AB1.5.3 Genetic crossesTeaching notesThe animation is designed for students to work        ...
B1 You and your genes Guidance AB1.5.4 Pairing upTeaching notesThis is a very quick, simple, activity to consolidate or   ...
B1 You and your genesGuidance AB1.5.4 Pairing up                        © University of York (UYSEG) and              This...
B1 You and your genes    Guidance AB1.5.5 Predicting inheritanceTeaching notesThe activity sheets present questions to pra...
B1 You and your genes Guidance AB1.6.1 Cystic fibrosisTeaching notesThis activity is an alternative to note-making which  ...
B1 You and your genes    Guidance AB1.6.2 Two inherited conditionsTeaching notesStudents should conclude for themselves th...
B1 You and your genes Guidance AB1.7.1 Shall we have the test?Teaching notesStudents are given four different scenarios an...
B1 You and your genes Guidance AB1.7.3 Decision makingTeaching notesIn this sequence of activities students develop a role...
B1 You and your genes    Guidance AB1.8.1 Finding the right medicineTeaching notesStudents are given a piece of extra read...
B1 You and your genes Guidance IB1.8.4 Genetic testing of adultsTeaching notesUse Presentation IB1.8.4 Genetic testing of ...
B1 You and your genes    Guidance AB1.9.2 Stereotype of the karyotypeTeaching notesThis is an extension activity.         ...
B1 You and your genes Guidance AB1.10.2 Embryo selection – what should be allowed?Teaching notesIn this activity students ...
B1 You and your genes    Guidance AB1.11.1 Asexual reproductionAnswers1     Unicellular.2     Asexual.3     Clones.4     T...
B1 You and your genes    Guidance AB1.11.2 Stem cellsTeaching notesThis activity introduces students to different         ...
B1 You and your genes Guidance AB1.12.1 Adult stem cellsTeaching notesStudents are given a sheet of comments giving them  ...
B1 You and your genes    Guidance AB1.12.2 The cloning debateTeaching notesThere are four scenarios for students to work w...
B1 You and your genes Guidance IB1.12.8 To clone or not to clone?Teaching notesStudents view the presentation and then com...
B1 You and your genes    Guidance AB1.A.1 Huntington’s diseaseTeaching notesThis activity introduces Huntington’s disease....
B1 You and your genes    Guidance AB1.B.1 Embryo selection is here to stayTeaching notesThis activity recaps students’ und...
B1 You and your genes    Guidance AB1.B.2 Inheriting genderTeaching notesThis activity reinforces students’ understanding ...
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B1 you and your genes answers

  1. 1. 2B1 You and your genes Guidance AB1.1.1 Inheritance traffic lightsTeaching notesThis activity is designed to review KS3 inheritance Requirements (per student)concepts and provide information on students’ • Activity sheet AB1.1.1 (optional)starting points for this module. • small pieces of card (x3) per student (eitherGive each student their cards. red, yellow, green or ×, , ?)• Red or × means FALSE.• Green or means TRUE.• Yellow or ? means I’M NOT SURE.The game follows this sequence:a Read the question.b Allow a short period of time for students to consider their answer.c Count ‘1, 2, 3, show your cards!’d Students all hold up one of their cards at the same time.The questions are available on Activity sheetAB1.1.1 if you wish to use them in a different type ofactivity.Answers to questions1 Sexual reproduction needs a male and a female. T2 Only animals use sexual reproduction. F3 Characteristics are passed on from parents to offspring in sexual reproduction. T4 In humans the male sex cells are called sperm and the female sex cells are called ova (or egg cells). T5 In some people there is an extra type of sex cell that produces identical twins. F6 In humans the sperm cell has a tail so it can move towards the ovum (egg cell). T7 Fertilisation happens when a male sex cell and a female sex cell join together. T8 The instructions to make a new person are in a fertilised egg cell nucleus. T9 These instructions are called genes. T10 All of a person’s characteristics are controlled by their genes. F11 Your blood group depends on what country you grow up in. F12 If you dye your hair red for more than two years, it will make you have red-haired children. F © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.1- 2 in the purchaser’s school or college
  2. 2. B1 You and your genes Guidance AB1.1.3 VariationTeaching notesThis activity reinforces students’ understanding of Requirementscauses of variation. • OHT sheets of graph axes (for teacher)Procedure • Activity sheet AB1.1.3 (optional-students)Ask the students to identify whether their earlobesare dangly or attached. d Height is also affected by your environment.Record the data as a block graph on the blank OHT e So people are not just either short or tall.axes. f People’s height varies much more than theirEmphasise lack of ‘inbetweens’. earlobe shape.Ask students to suggest other characteristics thatfollow this pattern (eg blood group). Many of theones students tend to suggest are not single-genecharacteristics (eg eye colour is determined byseveral genes). Most characteristics are determinedby several genes, and are affected by theenvironment.Superimpose provided graph of height data. Thisgraph shows height distribution for a population ofUK students aged 14–16.Ask students to suggest why the distribution looksdifferent, not simply ‘tall’ or ‘short’:• Height is determined by several genes – like most of our characteristics.• Height is also affected by environment – like many of our characteristics.You may wish some students to complete the activitysheet as a record of the key ideas. There areTextbook questions as an alternative.Further informationIf you have access to an interactive whiteboard youmay prefer to prepare graph axes on this, rather thanuse OHT sheets.Answers to questions1 Class data.2 a Graph shape showing two possible earlobe shapes. b Graph shape showing continuous data for height.3 a Person’s earlobe shape is affected by just one gene. b So you have either attached or dangly earlobes. c Your height is affected by many genes. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.1-3 in the purchaser’s school or college
  3. 3. B1 You and your genesGuidance AB1.1.3 Variation © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.1-4 in the purchaser’s school or college
  4. 4. B1 You and your genesGuidance AB1.1.3 Variation © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.1-5 in the purchaser’s school or college
  5. 5. B1 You and your genes Guidance AB1.2.1 Cloning plantsCloning cauliflower Requirements (per group)Procedure • Activity sheet AB1.2.1 (sheets 1 and 2)1 The working area should be swabbed with 70% • 100 cm3 sterile distilled water ethanol prior to the experiment. • 100 cm3 20% Domestos solution2 Once the cauliflower pieces have been sterilised • test tubes containing 2–3 cm3 plant tissue in bleach, quick, aseptic technique is needed to growth medium (x3) prevent contamination. • sterile Petri dish3 To flame metal instruments, dip them in alcohol, • metal forceps and scalpel (count out/back) pass briefly through a flame to ignite the ethanol. As the ethanol burns off, it heats the surface of • non-absorbent cotton wool the instruments to 70°C, killing any • aluminium foil contaminating organisms. Do not heat forceps • labelling pen and scalpels until red hot. • ethanol (for forceps/swabbing) (HIGHLY4 The cauliflower pieces can be left in the final FLAMMABLE) beaker of sterile distilled water (covered with a Petri dish lid) until required. Technical notes5 Before placing the cauliflower into each test tube, To make 775 ml of plant growth medium: remove the cotton wool plug, then briefly flame the • 20 g granulated sugar tube neck. Use flamed, cooled forceps to drop a • 10 g agar piece of cauliflower into the tube. Return the • 4.7 g Murashige and Skoog (M&S) medium forceps to the ethanol beaker. Flame the neck of the tube before replacing the cotton wool plug. • 25 cm3 kinetin stock solution6 The tubes should be kept in a warm, light place. The kinetin stock solution contains 0.1 g kinetin Growth should be visible within 10 days. in 1 litre of distilled water. Kinetin does not readily dissolve in water; adding one or two7 If contamination has occurred it will also be pellets of sodium hydroxide helps the dissolution visible by this time. Failure of any growth usually process. Stock solution should be stored at 4°C. indicates that the bleach solution has not been rinsed sufficiently from the plant tissue. Dissolve the sugar, M&S medium, and agar in 725 cm3 of distilled water. Mix in the stockFurther information kinetin solution, then dispense into test tubes (2–3 cm3 per tube). Plug the tubes with non-The procedure for cloning cauliflower is adapted absorbent cotton wool and cover the tops withfrom Practical Biotechnology, National Centre for aluminium foil. Autoclave at 121°C for 15Biotechnology Education (NCBE), 1995. Further minutes in a pressure cooker. When cool, theinformation and protocols for a wide range of school tubes may be refrigerated until they are needed.biotechnology practical work can be found on the M&S medium and kinetin are available fromNCBE website; see WEBLINKS. school science suppliers, e.g. Philip Harris Limited. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.2-3 in the purchaser’s school or college
  6. 6. B1 You and your genes Guidance AB1.2.1 Cloning plantsAnswers to questions11 To kill any microorganisms on the surface of the Health and safety notes cauliflower. Contamination of the growth medium Ethanol should be kept away from exposed could prevent the new plant from growing flames. You may wish to pre-prepare flamed properly. forceps and scalpels for students in some classes. Alternatively, they can be pre-sterilised12 To reduce water loss from the test tube. in an autoclave.13 Every plant cell contains all the genetic Plastic gloves should be worn when handling information needed to make a new plant. When kinetin – the solution used by the students the plant is growing, some of the plant cells stay present no problem. unspecialised. They can develop into any type of plant cell. Students should wear eye protection. Students need to take especial care when using scalpels. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.2-4 in the purchaser’s school or college
  7. 7. B1 You and your genes Guidance AB1.2.2 Twin studiesTeaching notesAs students work through this activity they practise Requirements (per student)converting data from a table to bar charts. The bar • Activity sheet AB1.2.2charts will then make it easier for them to draw • graph paperconclusions from the information they are given.The data comes from an early (1937) but importantUS study on twins, which showed how different To find outgenetic characteristics appear to be affected to a This provides extension for some students. Directgreater or lesser degree by environmental students to the weblinks provided for this lesson. Askinfluences. Subsequent studies have confirmed the them to find out more about twin studies. Look forconcept although there is still considerable variation evidence that students have extracted scientificin results. If anything, the consensus of data is that understanding from the twin stories, and that theygenes have a stronger influence than was originally recognise the type of data that would need to bethought, and environment less. collected to have validity, etc: see WEBLINKSStudents need to grasp the idea that, the smaller thedifferences between them, the more alike the pairare and so the stronger the genetic influence.This data suggests that height is surprisingly stronglygenetic, mass much less so and IQ clearlyinfluenced by both genes and environment.Answers1 Suitable bar charts2 Characteristic mainly decided by genes – environment has little effect, so little difference between identical twins reared apart or together. The bigger the influence of the environment, the bigger the difference between identical twins reared apart and identical twins reared together.3 Height – different environment has relatively small impact on final height of identical twins.4 They have identical genes but have been reared in different environments, so can see the effect of environment on different characteristics. This allows scientists to discover how much genes and the environment influence different characteristics.5 They are affected by the environment more or less equally.6 Any valid points, eg how many pairs of twins were studied, the age at which they were measured, if the data was all collected by the same people in the same place using the same instruments, etc. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.2-5 in the purchaser’s school or college
  8. 8. B1 You and your genes Guidance AB1.3.1 Inheriting genesTeaching notesThe animation (IB1.3.6) is designed for students to Requirements (per student or group)work through themselves. • Activity sheets AB1.3.1If you have access to an interactive whiteboard, you • Animation IB1.3.6may prefer to use a whole-class teaching approach.If you do not have access to the animation, studentscould complete the activity sheet using the Textbook.Answers to questionsFertilisation1 Humans have 23 pairs of chromosomes.2 The bands on the chromosomes show different genes.3 Chromosomes are in pairs, so genes come in pairs too.4 The only cells that don’t have pairs of chromosomes are the sex/gamete cells.Why don’t brothers and sisters look thesame?5 Sperm cells get a copy of just one of the chromosomes from each pair a man has.6 It is very unlikely that two sex cells get the same combination/mix of chromosomes.7 © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.3-3 in the purchaser’s school or college
  9. 9. B1 You and your genes Guidance AB1.4.1 Male or female?Teaching notesThe activity illustrates the random nature of Requirements (per student)fertilisation. Check that students know the sex • Activity sheet AB1.4.1chromosomes of a human male and female beforestarting the game. Students select randomly an Requirements (per group)‘ovum’ and ‘sperm’ card from each bag. The cards • small bag with 20 circles of card, eachshould be replaced in the bags and mixed well after marked with an X (‘ova’ bag)each ‘fertilisation’. • small bag with 20 sperm-cell shaped cards, half marked X and half Y (‘sperm’ bag)Answers to questions1 X or Y Technical notes2 All X It is helpful for clearing away if the ova and3 Sperm cell sperm cards are different colours.4 Students usually consider that Henry VIII was incorrect in blaming his wives for his lack of male heirs.Further informationStudents may be aware of anecdotal stories offamilies which appear to produce a greaterproportion of male or female children. The smallsample sizes within a family do not make this datasignificant. The 2001 UK census lists 28 581 233males and 30 207 961 females. There have beenindividual research reports that suggest spermcarrying a Y chromosome are more susceptible totoxins, such as those in cigarette smoke, than X-carrying sperm. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.4-2 in the purchaser’s school or college
  10. 10. B1 You and your genes Guidance AB1.4.2 Inheriting sexTeaching notesThe animation is designed for students to work Requirementsthrough themselves. • Activity sheet AB1.4.2 (per student)If you have access to a data projector or an • Animation IB1.4.4 Sexinteractive whiteboard, you may prefer to use awhole-class teaching approach. 4 A man’s sex chromosomes are XY.If you do not have access to the animation studentscould complete the activity sheet using the Textbook. 5 A human sex cell has 23 single chromosomes. 6 Row 1: XX XXAnswers to questions Row 2: XY XY1 A human body cell has 23 pairs of Chance of child being male: 50%; ½ chromosomes.2 Pair 23 control a person’s sex.3 A woman’s sex chromosomes are XX. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.4-3 in the purchaser’s school or college
  11. 11. B1 You and your genes Guidance AB1.4.3 Caster Semenya’s storyTeaching notesThis activity provides students with an opportunity to Requirements (per student)explore a contemporary story of an athlete where • Activity sheet AB1.4.3sex testing and gender issues meet. Caster • InternetSemenya is a young South African who has been • use WEBLINK to get students startedbrought up and schooled and has competed as agirl. However, once she appeared on both thenational and international stage, questions wereraised as to her biological sex as a result of both herappearance and her performances.In July 2010, a year after winning the gold medal, theInternational Association of Athletic Federations(IAAF) announced that its panel of medical expertsconcluded she could compete again.Students are asked to investigate the story andproduce a presentation or article summarising themain facts and the problems that have arisen. Itprovides another opportunity to discuss the sex/gender issues and also to consider how and why itmight have proved so difficult to determine whetherCaster is male or female. Use the WEBLINKavailable. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.4-4 in the purchaser’s school or college
  12. 12. B1 You and your genes Guidance AB1.4.4 Looking at sets of chromosomesTeaching notesThis is an extension activity. Requirements (per student or group) • Activity sheets AB1.4.4Answers to questions1 Pair 23 in a male body cell is XY; in a female body cell it is XX.2 The Klinefelter’s karyotype has three sex chromosomes instead of a pair – XXY.3 A person with Klinefelter’s is male because they have a Y chromosome with the gene for male sex hormone. So the embryo develops into a male.4 The instructions for how an organism develops are found in the form of genes found on chromosomes. Genes describe how to make proteins which might be structural or functional. If there are sections of genes missing or duplicated the proteins may not form or form incorrectly, affecting their function and causing the serious symptoms. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.4-5 in the purchaser’s school or college
  13. 13. B1 You and your genes Guidance AB1.5.1 AllelesTeaching notesThe animation (IB1.5.4) is designed for students to Requirements (per student or group)work through themselves. • Activity sheets AB1.5.1If you have access to an interactive whiteboard, you • Animation IB1.5.4may prefer to use a whole-class teaching approach.If you do not have access to the animation, studentscould complete the activity sheet using the Textbook.Answers to questions1 People have two copies of every gene because they inherit one copy from each parent.2 Different versions of a gene are called alleles.34 John has one allele for attached and one for unattached earlobes. The unattached allele is dominant. (You only need to have one dominant allele for a feature for it to show up.)5 Carl has two alleles for attached earlobes. (There is no dominant unattached allele, so he has the recessive feature.) © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-3 in the purchaser’s school or college
  14. 14. B1 You and your genes Guidance AB1.5.2 Modelling fertilisationTeaching notesThese activities are designed to clarify the distinction Requirements (per group)between gene and allele, and to illustrate that • Activity sheets AB1.5.2 (sheet 1fertilisation and the transfer of alleles from a pair into Foundation/sheet 2 Higher)sex cells are both random processes. Before • beads (e.g. plastic poppet beads) in twostarting, clarify with students what is meant by a contrasting colours (200 of each colour)‘scientific model’, i.e. to a scientist a model is a • beakers for the beads (× 3)simplified way of explaining how something is • marker pen or chalkarranged or how it functions. In this activity students • OHT of following guidance (for teacher)model the way information is passed on from parentsto their offspring using beads. Using these modelsthey test the ideas used to explain in theory how Health and safety notesdifferent characteristics are inherited – and see if It is probably worth mentioning not to put beadsthose ideas work. in mouth, ears, etc!To show that fertilisationhappens by chance (sheet 1) Using beads to show howa In this investigation the beads represent sex different alleles can be cells – the egg and sperm cells. Use red beads to be sperm, and yellow beads to be egg cells. inherited (sheet 2) Put all the 200 sperm beads in a ‘male’ a Students will make 100 new plants. Ask them to container, and all the egg cell beads in a ‘female’ predict the number of tall and short plants container. Mark 20 of the sperm beads and 20 of expected. the egg cell beads with a black spot. Put them b Put 100 red and 100 yellow bead ‘alleles’ in the back in their containers and mix them in with the ‘male’ container and mix them up well. Do the unmarked beads. same for the ‘female’ container to show theb Pull out one sperm and one egg bead without alleles in the female sex cell. looking. These two beads represent the fertilised c Take one bead from each container to egg cell. Record if either bead carries a black determine the alleles in the new plant. Students spot on the tally chart. use a tally chart to record the pair – 2 red, 1 redc Students will make 50 fertilised eggs. Ask them and 1 yellow, or 2 yellow. to predict how many pairs of beads will have: d Replace the beads in the container they came • a black spot on just one bead from each time. • black spots on both beads Answers to questions • no black spots at all 1 & 2 These will depend on the predictions made. 3 How well they were mixed. Whether studentsAnswers to questions looked in the beaker when they picked.1 This depends on the predictions made. These simulation exercises work well, but it is2 In the experiment it was chance which bead you important to make sure that students are clear about picked up each time. what the beads and beakers are representing in Fertilisation is like that too. each case. It is particularly important that the You cannot predict which sperm will fertilise an concepts of genes and alleles are explained egg cell. carefully, as students often get these confused. Students need to make a fairly large number of fertilised ova for the statistics to work. This does not add much to the time required for the activity. Alternatively, collect group results into whole-class data. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-4 in the purchaser’s school or college
  15. 15. B1 You and your genes Guidance AB1.5.2 Modelling fertilisationUsing beads to show how different allelescan be inheritedPea plants are either tall or short. Their height is controlled by just one genewith two different possible alleles. The tall allele is dominant. The shortallele is recessive. (This is different from humans. Human height is affectedby many genes.)In this investigation you are going to model the breeding between two tallplants. Both these tall plants had one tall and one short parent. You will usebeads to represent the alleles for tall and short, e.g. red for tall, yellow forshort. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-5 in the purchaser’s school or college
  16. 16. B1 You and your genes Guidance AB1.5.3 Genetic crossesTeaching notesThe animation is designed for students to work Requirements (per student)through themselves. • Activity sheet AB1.5.3If you have access to an interactive whiteboard, you • Animation IB1.5.5may prefer to use a whole-class teaching approach.If you do not have access to the animation, studentscould complete the activity sheet using the Textbook.Answers to questionsGenetic crosses © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-6 in the purchaser’s school or college
  17. 17. B1 You and your genes Guidance AB1.5.4 Pairing upTeaching notesThis is a very quick, simple, activity to consolidate or Requirements (per class)recap students’ knowledge of symbol representation • Activity sheets AB1.5.4 (one or more sheetsfor dominant and recessive alleles. per student)Depending on class size, give each student one or • OHT of animal outlines copies (x5)more chromosome cards until all are distributed. • packs of OHT pens of various colours (x5)The task is to find their matching chromosome pair,and mark the OHT animal with the feature the alleles Technical notesdetermine. A set of chromosome cards could be cut outThere are five animal outlines. Give one OHT sheet and laminated before the lesson.to each of five students around the room. They arethe base for that animal.When students find their matching pair, theyannotate the feature on the OHT sheet.Use the completed OHT sheets as a basis for quickcheck questions, eg what would this feature havebeen if the animal had different allele pairs? © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-7 in the purchaser’s school or college
  18. 18. B1 You and your genesGuidance AB1.5.4 Pairing up © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-8 in the purchaser’s school or college
  19. 19. B1 You and your genes Guidance AB1.5.5 Predicting inheritanceTeaching notesThe activity sheets present questions to practise Requirements (per student)genetic crosses. The later questions have less • Activity sheets AB1.5.5student support. You will want to select questionsmost appropriate to your students.The final sheet has blank Punnett square diagrams 4to support students if required on the more difficultquestions.Answers to questions1 a b Short plant must have alleles tt. The percentage of tall plants is 50%.23 © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.5-9 in the purchaser’s school or college
  20. 20. B1 You and your genes Guidance AB1.6.1 Cystic fibrosisTeaching notesThis activity is an alternative to note-making which Requirements (per student)may be appropriate for some students. Students • Activity sheet AB1.6.1identify symptoms and treatments for cystic fibrosis. • Animation IB1.6.7 (optional)The second sheet has instructions which you mayprefer to photocopy, or alternatively display onOHT/whiteboard for students to follow.The first part of Animation IB1.6.7 Reading the geneshows the location of the lungs and pancreas, andillustrates mucus build-up along lining tissue. It maybe useful to show this briefly to the class. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.6-3 in the purchaser’s school or college
  21. 21. B1 You and your genes Guidance AB1.6.2 Two inherited conditionsTeaching notesStudents should conclude for themselves that cystic Requirements (per student)fibrosis is determined by a recessive allele. • Activity sheets AB1.6.2Answers to questions b The allele for cystic fibrosis is recessive.1 A person with one copy of the allele will not Name of Huntington’s Cystic have the disorder. disorder disease fibrosis They are a carrier. Key H = Huntington’s F = normal The allele for Huntington’s disease is allele allele dominant. h = normal allele f = cystic A person with one copy of the allele will fibrosis allele have the disease. So there are no carriers of Huntington’s Does one of disease. the parents of the affected yes no people also have the disease? What are the allele pairs of people HH or Hh ff with the disorder? What are the allele pairs of people hh Ff or FF without the disorder?2 A recessive allele will only cause an effect when there are two of them.3 a Huntington’s disease: there are no carriers. Cystic fibrosis: Rob, Jane, Paula and Keith must be carriers for the cystic fibrosis allele. Some students may understand that Leon and Clare, and Owen, could be carriers. We cannot be certain they are not from the information in the family tree. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.6-4 in the purchaser’s school or college
  22. 22. B1 You and your genes Guidance AB1.7.1 Shall we have the test?Teaching notesStudents are given four different scenarios andasked to plan the advice they would give to the Requirements (per group)couples who are all concerned about having fetal • Activity sheets AB1.7.1genetic testing for different reasons. Students can • OHT of possible viewpoint (or student copies)work in small groups or individually. • Internet access or printed web pages withHelp students to understand that the advice given background information on reliability ofwill vary from couple to couple depending on their genetic testing (optional – also provided incircumstances and the importance of the Textbook sections E & G)information they are seeking. They also need tosuggest that couples consider whether they wouldproceed to a termination if they found there was aproblem with the fetus. In one instance in particular,where the parents are simply desperate to know thesex of the unborn baby, the risks of the testoutweigh the benefits of the knowledge and they willprobably be able to find out a little later in thepregnancy with an ultrasound scan and virtually norisk.Useful websitesThe websites provided are for the Royal College ofObstetrics and Gynaecology; and genetics ingeneral. They are very clear and informative aboutchorionic villus sampling and amniocentesis: seeWEBLINKS © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.7-2 in the purchaser’s school or college
  23. 23. B1 You and your genes Guidance AB1.7.3 Decision makingTeaching notesIn this sequence of activities students develop a role- Requirements (per group)play to explore the ethical issues surrounding pre- • Activity sheet AB1.7.2natal testing for a genetic disease. • Activity sheet AB1.7.3There are three roles within each group: a couple • OHT of possible viewpoint (or student copies)and their genetic counsellor. When grouping • Internet access or printed web pages withstudents, keep in mind that the role of genetic background information on reliability ofcounsellor will need a reasonable grasp of the genetic testing (optional – also provided inscience ideas. Textbook sections F & G)The first activity is a small-group discussion of theoptions available to the couple. A summary (in theform of a flowchart) of the available options for the viewpoints that they may not be in agreement with.couple is provided at the end of these notes to copy Possible viewpoint statements which you could useonto OHT or give to students. As this is the first with students are listed at the end.occasion during the module that students focus in Students should then be given a set time period todepth on the Ideas about Science explored in this prepare and present their role-play.module, they are likely to need help in structuringtheir discussion. This is provided by the table on Useful websitessheet 2 of the activity. Alternatively, if you wish to The Guardian website has a special report ongive students less structured support, you could use genetics and ethics covering a wide range of issues:AB1.7.2 Ethics. see WEBLINKS.The table on sheet 2 can be completed by onemember of the group as a record of their researchand discussion. It focuses students on the keyinformation they need to consider before developingtheir role-play. At the end of their discussion eachgroup should have ranked the options available tothe couple. Differences in opinion are likely, but agroup should try to reach agreement if they can. Ifthis is not possible, students should reflect thiscontroversy in their role-play.When students hold strongly opposed viewpoints itcan be useful to step in and bypass the rankordering. Sensitivity to this possibility is importantwhere, for example, any questioning of a firmly heldfamily position may be considered as an insult tostudents’ family beliefs. Controversy involves values,so it is reasonable to set the discussion in thecontext of respect for each other, acting in theinterests of the group by listening to opposing views,and prohibiting remarks which may be offensive toother members of the class.It is worth reminding students that they are going tobe expressing views in the context of a role-play, andthat therefore these views are not necessarily theirown. Perhaps suggest to different groups that thetwo people within each couple are in broadagreement, or that they disagree. In this waystudents are directed to consider and present © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.7-3 in the purchaser’s school or college
  24. 24. B1 You and your genes Guidance AB1.8.1 Finding the right medicineTeaching notesStudents are given a piece of extra reading about Requirements (per student)pharmacogenomics and then asked to answer a • Activity sheet AB1.8.1series of questions. Questions are provided at F and • InternetH levels.Answers F 5 Any two sensible ideas, for example:1 All of the human genes • It allows doctors to use the minimum effective dose of drug for each patient, which minimises2 The science of developing new medicines using risk of side effects and saves NHS money by knowledge about drugs/pharmaceutical reducing drug bill. expertise and information on the human • It means doctors only prescribe drugs which genome/individual genetic makeup. are effective for a particular patient – benefits3 Certain painkillers/ kappa opioids work better for patient as always given effective drug and females than males. OR Many over-the-counter saves NHS money by avoiding trying drugs painkillers work best in pale-skinned, red-haired which don’t work for patient. women. • It avoids adverse drug reactions. This benefits4 Only giving drugs to which you will not have a patients – they don’t risk death or hospital bad reaction. Calculating the lowest effective admission – and saves NHS money treating dose. the result of adverse drug reactions.5 Costs lots of money to develop personalised 6 It costs lots of money to develop personalised medicines – to sequence the genome and find medicines – to sequence the genome and find the right medicines. Drug companies might not the right medicines. Drug companies might not do this for developing world countries which do this for developing-world countries which might not be able to afford the individual testing might not be able to afford the individual testing to use the specific drugs. Is it ethical if it is to use the specific drugs. Is it ethical if it is possible to develop drugs but they don’t do it? possible to develop drugs but they don’t do it? Any valid points which show student has thought Any valid points which show student has thought about potential difficulties. about potential difficulties. 7 Any thoughtful point, eg in some cases one drugAnswers H will work for the majority of people. If only a1 All of the human genes small group need an alternative, it won’t be2 The science of developing new medicines using financially viable for drug companies to develop knowledge about drugs/pharmaceutical an alternative drug. Should they be forced to do expertise and information on the human so? Or should people with the minority genetic genome/individual genetic makeup. sequence be left without effective treatment?3 Certain painkillers/kappa opioids work better for females than males. OR Many over-the-counter painkillers work best in pale-skinned, red-haired women.4 If they know the genome sequence of normal cells and cancer cells they can develop drugs which target only the cells with the changed genetic material of the cancer cells. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.8-2 in the purchaser’s school or college
  25. 25. B1 You and your genes Guidance IB1.8.4 Genetic testing of adultsTeaching notesUse Presentation IB1.8.4 Genetic testing of adults 1 Requirements (per student)to introduce genetic testing of adults and the ethical • Presentation IB1.8.4issues this raises. In this case testing adults before • Whiteboard and projectorthey start a family has prevented any babies withTay Sachs disease being born in the US, Israel orthe UK.Slide 1: IntroductionSlide 2: Image of crowd. Text reminds students thateveryone has faulty genes with dangerous allelesbut most of the time they don’t cause problems. Askstudents when these alleles do cause problems.Answers should include: when the problem is adominant allele or when two people carrying thesame recessive faulty allele have a child.Slide 3: Introduction to Tay Sachs disease tosupport book content. As always with geneticdiseases, this needs sensitive handling. However, asa result of the genetic screening described, it ishighly unlikely that any pupils will have had anyexperience of this genetic condition in their familiesin recent years. Point out that it is the lack of a singleenzyme that causes all the problems.Slide 4: Rabbi Joseph Ekstein devised the screeningprogramme in response to losing four of his ownchildren to Tay Sachs. There is a screening testwhich shows up carriers and this made theprogramme possible.Slide 5: Punnett square showing how two carrierscan pass on the lethal combination.Slide 6: Since the 1980s, Jewish couples ofEuropean descent have taken genetic tests and, asfar as possible, two carriers have not been matched.You could explain to students that in more traditionalJewish communities a matchmaker would arrangecouples and so this made it easier to avoid matchingtwo carriers. Carriers who marry use pre-natal fetaltesting and termination to prevent the birth ofaffected children.Slide 7: Highly successful – virtually no babies withTay Sachs have been born in the US, Israel or theUK in recent years. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.8-3 in the purchaser’s school or college
  26. 26. B1 You and your genes Guidance AB1.9.2 Stereotype of the karyotypeTeaching notesThis is an extension activity. Requirements (per student) • Activity sheet AB1.9.2Answers to questions1 Male sex cells usually have XY chromosomes.2 Human body cells normally contain 46 chromosomes.3 An XYY person has 47 chromosomes in each body cell.4 Three unusual phenotypes of XYY men are: • minor out-turning of the elbows • pectus chest deformity • crooked left eye5 The insurance company may think that he is more likely to show violent behaviour, and thus become injured. They may think that his chest deformity or crooked eye may make him more likely to need health treatment.6 John’s bad behaviour could be due to his diet rather than just being because he is XYY. The fact that he is XYY does not mean that this is the cause of his bad behaviour.7 No, because: • XYY men are tall so they are more noticeable and may therefore be targeted more for fights, or be more memorable to people – making them more likely to be arrested. • Most XYY men are not in prison, so all XYY men are not criminals.8 A stereotype is a ‘label’. The XYY stereotype labels all XYY men as ‘likely to be violent criminals’. XYY men are mostly decent, good people, so the stereotype is unfair and unjust. When we label people as ‘abnormal’ in some way we may make assumptions about them which are not true. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.9-2 in the purchaser’s school or college
  27. 27. B1 You and your genes Guidance AB1.10.2 Embryo selection – what should be allowed?Teaching notesIn this activity students take on the role of a Requirements (per group)government regulatory body (currently, September • Activity sheets AB1.10.22010, the Human Fertilisation and Embryology • Activity sheet AB1.7.2Authority: see WEBLINKS • access to Internet (optional – depending onTeachers should visit the above website, to make time allocated to the activity)sure that they know the current rulings as thesechange. In summary, PGD is allowed for serioussingle-gene disorders such as cystic fibrosis; toselect for an embryo which is a tissue match for a Notesseriously ill child; in sex-selection for medical Pre-implantation genetic diagnosis (PGD): this isreasons but not for family balancing. a recent alternative treatment. It was first introduced in 1990 for gender selection of embryos in cases ofEnsure that students are clear about the role of the sex-linked inherited diseases. In 1992 PGD was firstregulatory body before beginning the activity. If time successfully used in a case of cystic fibrosis. Allpermits, more able students could be asked to applications to use PGD must currently be approvedresearch this information themselves. The relevant by the regulatory body.websites may not be accessible for all students.Alternatively, a summary card is provided in the Friedreich’s ataxia: particularly recommended isactivity sheets. ‘The Gift’, a video drama based around the issue of embryo selection, from the Wellcome TrustStudents should work in groups of four. It does not Education page. Set both in the present and 30matter if there are extra students. Allocate each years in the future, it explores the options availablestudent in the group a ‘Case’ card 1–4. to three generations of a family affected by the rareRearrange the class so that all Case 1 students are genetic disorder, Friedreichs ataxia.together and so on. Human Fertilisation and Embryology AuthorityUsing AB1.7.2 Ethics as guidance, students consider (HEFA): the HFEA is one of the few statutory bodieswhether embryo selection should be allowed in their worldwide which regulates, licenses and collectscase. The activity sheets include a table for them to data on fertility treatments such as IVF and donorrecord their views. insemination, as well as on human embryo research.Students should have a set time limit to discuss their It was set up in 1991 to monitor and inspect allcase so that they can present it to their group. At the clinics in the UK offering fertility treatments or storingend of this time they should be able to: eggs, sperm, or embryos.• explain what the case is The HFEA consists of 21 members appointed by UK• say what the expert group decision was Health Ministers. Members should not be selected as• explain the reasons for the decision, with representatives of a particular organisation, but in reference to the ethical framework on AB1.7.2. respect of their personal expertise. At least half of the HFEA members come from disciplines other thanIn their group of four, they are the ‘expert’ on their case. medicine or human embryo research. They shouldRunning the activity in this way is therefore less be appointed in line with the Nolan principles, seventhreatening for students than presenting their views to a guidelines for individuals holding public office:larger audience. This would be an alternative approach www.ost.gov.uk/policy/advice/copsac/annex.htm.where students are more confident. The HFEA has carried out public consultations toSome students will not agree with embryo selection gather views on pre-implantation genetic diagnosis,in any case. They should be encouraged to argue and its use in gender selection. The consultationtheir case within the bounds of this role-play, i.e. documents are available on its website at time ofembryo selection is allowed subject to regulation. press, and they are very useful sources ofAs a member of the regulatory panel, they must information about this technology.develop arguments to win over their colleagues inparticular cases, thus restricting the use of embryoselection as much as they are able to. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.10-3 in the purchaser’s school or college
  28. 28. B1 You and your genes Guidance AB1.11.1 Asexual reproductionAnswers1 Unicellular.2 Asexual.3 Clones.4 The environment is also a source of variation. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.11-3 in the purchaser’s school or college
  29. 29. B1 You and your genes Guidance AB1.11.2 Stem cellsTeaching notesThis activity introduces students to different Requirements (per student or pair)viewpoints on embryo cloning, and recaps the • Activity sheet AB1.11.2decision-making ethical framework introduced • Scissors and gluethrough the Ideas about Science in this module. • Computer and printer access (optional – asThe first sheet of the activity presents a number of alternative to cut and stick)viewpoints for/against cloning embryos to producestem cells for potential medical treatments. b Opinion: This treatment could relieveStudents should separate the arguments into for and diabetics from injecting synthetic insulin.against piles then distinguish them by type: However, this treatment is unlikely to be a• decision made by weighing up consequences for cure. all involved 5 No, this account seems impartial.• decision made because process is considered fundamentally right or wrong. 6 Ethical arguments in relation to using embryosThe second page of the activity sheet introducesstudents to some of the language they will meetthroughout GCSE Science when discussing ordeveloping arguments: opinion, speculation,evidence, explanation, fact.The first question introduces the terminology to theclass.If you have copies of a recent news story, extend thisintroduction by asking students to identify keystatements in the report.The terminology is then put in the context of stemcells and diabetes.Answers1 Opinion - Someones viewpoint. May not be based on evidence. Speculation - Suggesting possibilities that might happen. Goes beyond facts. Evidence - Information that is linked to the issue. Explanation - An idea to explain some evidence. Fact - Something that people accept as being proved true3 a Description: transplants of stem cells from their own bone marrow b Evidence: Out of 23 patients, 20 no longer required insulin injections. One patient remained insulin-free for up to 4 years. Speculation: This treatment could relieve diabetics from injecting synthetic insulin4 a Explanation:This is because the cells that make insulin are all destroyed after that time. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.11-4 in the purchaser’s school or college
  30. 30. B1 You and your genes Guidance AB1.12.1 Adult stem cellsTeaching notesStudents are given a sheet of comments giving them Requirements (per student)information and opinions about adult stem cells. • Activity sheet AB1.12.1They use these sheets along with the Textbook, ifneeded to fill in the table provided. This could alsobe done as a class exercise, filling in the tabletogether and using the process as a basis fordiscussion about the ethical issues raised by bothprocesses.There are many different valid and sensible pointswhich could be raised – a few possibilities are givenhere.Possible answers Embryonic stem cells Adult stem cells Large numbers can be Only found in tiny produced numbers Relatively easily grown Relatively difficult to grow Cells very flexible – can be Cells can be used to used to produce very wide produce a more range of tissues limited range of tissues Cells relatively undamaged Cells may have DNA damage – mutations – depending partly on the age of the adult Tissues formed may be Tissues formed have rejected – recipient needs same antigens as immunosuppressant drugs original cells so no rejection problems Ethical issues for some No ethical issues as people with using cells taken from embryonic cells patient © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.12-2 in the purchaser’s school or college
  31. 31. B1 You and your genes Guidance AB1.12.2 The cloning debateTeaching notesThere are four scenarios for students to work with. Requirements (per student)Depending on the size and ability of the class, • Activity sheet AB1.12.2students can work individually or in groups. They • Internet accessmay manage only one of the activities during thelesson or they may work through all four! Some ofthe activities can be completed more successfully C Cloning endangered or extinct animalswith access to ICT; if it is not available students will 1 No living tissue to get DNA from; high-qualitybe more limited in the scope of their answers. fossils rare; difficulties of getting DNA fromIn most of these answers students are required to extinct animals; no animals of the same speciesexpress opinions as well as report biological facts. to provide eggs or act as surrogate mothers;Answers different habitat, food resources, etc. Any sensible points.A Cloning farm animals and animals for 2 Look for evidence that students understand bothmedicines the science and the concept of ethicalStudents should show awareness of the benefits of arguments, and that they present argumentscloning of top-quality animals and embryo cloning in both for and against the processes.farm animals, and the importance of adult cellcloning in producing as many animals which give D Cloning humansmedicines in their milk as possible. Disadvantages Look for evidence of a good understanding of theinclude the small numbers of animals which result, ideas both for and against the process, and anthe risks and problems of adult cell cloning, etc. awareness of technical difficulties, biologicalStudents should show clear understanding of dilemmas and ethical problemsdifferent ethical positions.B Cloning pets1 a Different environment – different mother, different uterus, different time so different foods, etc will be available. Environment affects the phenotype as well as the genotype so the animal is likely to have a different character – and behave differently – it will have different experiences, etc. Cats’ coats, even with identical genes, can have a very different pattern and colour, so the clone may not look the same as the original. Any other sensible points. b Look for biological and ethical comments in student’s answers to this question.2 a The foal will be genetically identical to the original champion horse but will be a stallion and therefore able to act as a stud when it is adult, so high-quality genes can be passed on. It can make a lot of money for the owners. Any other sensible points. b Any sensible and thoughtful points. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.12-3 in the purchaser’s school or college
  32. 32. B1 You and your genes Guidance IB1.12.8 To clone or not to clone?Teaching notesStudents view the presentation and then complete Requirements (per student)Activity AB1.12.2 The cloning debate. • Presentation IB1.12.8 • Activity AB1.12.2Slide 1: To clone or not to clone?Students are introduced to the idea that many Slide 8: Cloning race horses?species of animals have been cloned and thatcloning can be used in very different ways. They are This image shows a foal who is a clone of a highlygoing to look at some of the decisions that need to successful endurance champion who is a gelding.made about this fast-developing technology. Race horses are often gelded, though if they then become extremely successful they cannot be used atEmphasise, that in most of the examples described, stud. But if the gelded horse is cloned, the foal willit is adult cell cloning that is the basic technique. be a stallion and can be used for breeding.Slide 2: Dolly the sheep Slide 9: Cloning endangered speciesImage of Dolly the sheep with her own first lamb, Scientists have tried to use cloning to increase theBonnie. This reminds students that adult cell cloning numbers of some of the most endangered species ofis not easy. It took 277 eggs to produce 1 live lamb. animals. There was great excitement when Noah theSlide 3: Cloned cattle baby gaur (a very rare breed of wild cattle) was born. Unfortunately, he died of infection within 2 days of birth.Reminder that cattle are often cloned by embryo Cloning mouflon (rare wild sheep) has been morecloning (when a single embryo is split into lots of successful. But very few endangered animals haveindividual cells, which each develop into another been cloned. One problem is that animals which areembryo to be implanted in a surrogate mother cow). closely related but not the same species usually haveThe cows on the slide were produced by the less to act as both egg donors and surrogate mothers.common method of adult cell cloning. Slide 10: Cloning extinct organismsSlide 4: The first dog clone This slide shows an almost perfect fossil of a babyThe first dog to be cloned was produced in South mammoth found in the Siberian permafrost in 2007.Korea in 2005. The photo shows Snuppy the clone Scientists think that it may one day be possible toas a puppy alongside the original dog. The scientist clone extinct animals form DNA extracted fromwho produced Snuppy was later disgraced because extremely well-preserved fossils like this one. Againhe faked evidence in work on human stem cells. one problem is that animals which are closely relatedHowever, DNA testing proved that Snuppy really was but not the same species would have to act as botha clone. egg donors and surrogate mothers. Also the environment, food supply, habitat, etc of extinctSlide 5: Cloning pets 1 animals no longer exists.This slide shows CopyCat, the first cat to be clonedsuccessfully, and Little Nicky, the first pet cat to be Slide 11: Cloning primatescommercially cloned. Cloning primates is proving much more difficult than cloning most other mammalian species, althoughSlide 6: Cloning pets 2 early embryos and embryonic stem cells wereThis slide shows an American couple with the first produced in 2009.commercially produced cloned pet dog – all£100,000 worth of him! Slide 12: Human clones The final slide simply raises the issue of humanSlide 7: Cloning horses clones – not only whether it can be done (so far theThe first cloned horse, who was both daughter and answer is no although one or two maverick scientistsidentical clone of the mare who gave birth to her. claim to have tried) but whether it should be done. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.12-4 in the purchaser’s school or college
  33. 33. B1 You and your genes Guidance AB1.A.1 Huntington’s diseaseTeaching notesThis activity introduces Huntington’s disease. It is Requirements (per student)supported by Section C in the Textbook. • Activity sheet AB1.A.1Answers to questions1 Both men and women can suffer from Huntington’s disease. Only one parent needs to have the condition for it to be passed on to their children.2 a Huntington’s disease is an inherited condition. Eileen thinks that David is more likely to have inherited the condition because he looks a lot like his dad. b Sarah is just as likely as David to have inherited the condition from their dad. It has nothing to do with what other features they may have inherited. c No – it’s a bit late. Symptoms of Huntington’s disease are usually noticed between ages 35 and 50 years. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.A-2 in the purchaser’s school or college
  34. 34. B1 You and your genes Guidance AB1.B.1 Embryo selection is here to stayTeaching notesThis activity recaps students’ understanding of Requirements (per student)embryo selection. • Activity sheets AB1.B.1Students should have met the terminology in an • coloured pens/pencilsearlier lesson. However, there is sufficient guidancefor students if they have not done so.Answers to questions1 Definition of IVF: Paragraph 4 ‘fertilise the egg outside the woman’s body’.2 Description of choosing embryos: Text with diagrams at bottom of article.3 Fact: In 1989 scientists found the gene for cystic fibrosis. Speculation: some said we were close to a cure.4 ‘This method throws away human beings.’ ‘Embryos are a group of cells. They aren’t conscious.’5 eg Fact: ‘Fifteen years on we still don’t have one.’ eg Speculation: ‘Soon they’ll be offering embryo testing for features like eye colour or height.’ eg Opinion: ‘Couples that test the embryos for a disease gene are just giving their children a helping hand.’6 The final sentence expresses a positive view of PGD suggesting that the author is in favour of its use. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.B-2 in the purchaser’s school or college
  35. 35. B1 You and your genes Guidance AB1.B.2 Inheriting genderTeaching notesThis activity reinforces students’ understanding Requirements (per student)of gender determination. • Activity sheet AB1.B.2Answers to questions1 ovum Sperm X X cell X XX XX Y XY XY2 a Reference to girls having two X chromosomes. A faulty recessive allele will not display its characteristic where there is a normal dominant allele present on the other X chromosome. Boys have only one X chromosome, so a faulty recessive allele will always be displayed. b Haemophilia was recognised as an inherited disease which could be passed on from one generation of a family to the next. c i Michael and Bob have haemophilia. ii Lesley and Melissa are carriers of haemophilia. iii Sara, Leanne, and Kara may be carriers of haemophilia. iv Darren, Mark, Peter, and James are not affected by haemophilia. © University of York (UYSEG) and This page may be copied solely for use the Nuffield Foundation B1.B-3 in the purchaser’s school or college

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