Sexual reproduction links with 4.6.2.3, Selective breeding. Asexual reproduction links with 4.1.2.2, Mitosis and the cell cycle. There are also links with 4.1.1.4, Cell differentiation. Chromosomes and Mitosis (4.1.2.1 and 4.1.2.2) should be reviewed when teaching Meiosis. Protein synthesis links with enzyme action in 4.2.2.1. It be sensible to teach Sex determination, 4.6.1.6, after sexual and asexual reproduction and before DNA and genes, in 4.6.1.3. This would begin the story at the level of chromosomes, which have been introduced in meiosis, and also leads on from single chromosomes coming together as pairs at fertilisation. 4.6.1.5, Inherited disorders links with 4.6.2.4, Genetic engineering to treat genetic disorders. 4.6.2.4, Genetic engineering, could be taught after inheritance, rather than with 4.6.2 Variation and evolution. Spec ref. Summary of the specification content Learning outcomes What most candidates should be able to do Suggested timing (hours) Opportunities to develop Scientific Communication skills Opportunities to apply practical and enquiry skills Self/peer assessment Opportunities and resources Reference to past questions that indicate success 4.6.1.1 Sexual and asexual reproduction Sexual reproduction involves the joining (fusion) of male and female gametes, sperm and eggs in animals and pollen and ovule cells in flowering plants. This mixing of genetic information leads to variation in the offspring. Explain why sexual reproduction produces variation in the offspring, but asexual reproduction does not. Describe sexual reproduction in animals and plants. Define the term 1 Recap of reproduction through group work to discuss and share answers to questions: Do we really need males? Is sex necessary? Can scientists solve the world food shortage? Do hermaphrodites lead a solitary existence? Watch BBC video clips of fertilisation in humans and Appreciate how scientific developments can be used to control reproduction. Exhibition: strawberry runners carrot top growing on damp blotting paper potato sprouting
set of chromosomes. All gametes are genetically different from each other. Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis, and as the embryo develops differentiate. gametes during meiosis and fertilisation. Describe how an embryo is formed. Compare mitosis and meiosis (links with 4.1.2.1 and 4.1.2.2). Watch BBC video clip and access information on mitosis and meiosis (see resources). Produce a poster to compare mitosis and meiosis. 4.6.1.6 Sex determination Human body cells contain 23 pairs of chromosomes. 22 pairs control characteristics only. The 23rd pair carries the genes that determine sex. In females the sex chromosomes are the same (XX); in males the Explain using a Punnett square and genetic diagram how sex is determined in humans. Explain the probability of having a child that is a boy or a girl. 0.5 Look at male and female karyotypes and identify the number of of chromosomes and each pair of sex chromosomes. Use ‘Making Reebops’ game to demonstrate variation (see resources). Watch BBC video clip about Sex chromosomes (see resources). Use a Punnett square and a genetic cross diagram to illustrate the inheritance of sex; ‘Making Reebops’ practical. Video clip:
chromosomes are different (XY). evaluate the chance of producing a male or female. 4.6.1.3 DNA DNA is a polymer made up of two strands forming a double DNA is found in chromosomes. A gene is a small section of DNA. Each gene for a sequence of amino acids to form a particular protein. The genome is all the genetic material of an organism. The genome has been studied and will be important for medicine in the future. Describe the structure of chromosomes, DNA and genes. Explain that a gene is a small section of DNA that codes for a particular sequence of amino acids to make a specific protein. Describe what the genome is. Explain how knowledge of the human genome will help medicine in the future, eg identifying genes linked to cancers, understanding and treating inherited disorders. It will also help trace human migration patterns. Explain the ethical issues related to DNA sequencing. 1 Recap key ideas by asking students to reorder by size: cell, nucleus, DNA, chromosome, gene, nucleotide. Debate: research and discuss ‘DNA profiling’ for health. Research roles of Franklin, Watson and Crick in the discovery of the structure of DNA. Demo or practical to extract DNA. Appreciate the power and limitations of science and consider any ethical issues. Extract DNA from fruits such as onions or kiwi fruit. Observe the long strands which are the polymer. Ethical issues:
4.6.1.4 4.6.1.5 If the two alleles present are the same the person is homozygous for that trait, but if the alleles are different they are heterozygous. Most characteristics are a result of multiple genes interacting. Some disorders are inherited, eg polydactyly and cystic fibrosis. A Punnett square can be constructed to predict the outcome of a monohybrid cross. genotypes and phenotypes of the offspring. Describe the inherited disorders polydactyly and cystic fibrosis. Use genetic cross diagrams to explain inheritance and carriers. Make informed judgements about the economic, social and ethical issues concerning embryo screening. Discuss the use of genetic modification to treat genetic disorders (links with 4.6.1.4). HT: Construct Punnet squares and genetic crosses. Evaluate genetic modification to treat cystic fibrosis. Produce notes and complete genetic diagrams to explain how polydactyly and cystic fibrosis are inherited. Interpret genetic diagrams relating to these disorders. Role play – choices for parents of a cystic fibrosis sufferer who would like another child. To involve experts explaining cystic fibrosis and the screening procedure; the child with the disorder; parents to discuss what they would do if the foetus had the disorder. Or Watch a video of the process and describe issues to be considered re embryo screening. clip:
4.6.2.4 Genetic engineering Genetic engineering involves modifying the genome of an organism to introduce a desired characteristic. can be cut from the chromosome of a human or other organism and transferred into the cells of other organisms. HT: enzymes are used to cut the gene from a chromosome; gene is inserted into a vector, eg bacterial plasmid or virus; vector is used to insert gene into cell; cell then makes a new Define the term genetic engineering. Describe the process of genetic engineering and its advantages. HT: Describe in detail the process of genetic engineering. Evaluate the use of genetic engineering in medicine, eg in gene therapy and production of hormones and some vaccines. Interpret information about genetic engineering techniques. Make informed judgements about the economic, social and ethical issues concerning genetic engineering and GM crops. Explain advantages and disadvantages of genetic engineering. 1–2 Brainstorm what the terms genetic engineering, genetic modification and gene therapy mean. List examples of genetic engineering. Produce a leaflet for a doctor’s surgery to explain how human insulin is produced by bacteria and discuss the advantages of this over porcine insulin. Interpret information about genetic engineering techniques. Research advantages and disadvantages of GM crops. What characteristics may be modified? Produce a web page or a table of benefits versus concerns for homework. Produce headline paragraphs to represent the views of organic farmers, organisers, GM Research scientists and students. Use a model to describe genetic engineering techniques. Evaluate the use of genetic engineering in agriculture and medicine. Information on genetically modified food can be found at
illness that could be linked to environment? Eg, high cholesterol levels in family. Discuss the benefits of knowing how can be linked to diseases. 4.6.2.3 4.6.2.3 Selective breeding Selective breeding (artificial selection) is the process by which humans breed plants and animals for useful characteristics. The steps involved in selective breeding. Selective breeding of food plants has produced disease or weather resistant crops, more attractive or better flavoured fruits and crops that are easier to harvest. Selective breeding of animals has produced cows that Explain why humans selectively breed plants and animals. Describe selective breeding as a type of sexual reproduction. Describe the process of selective breeding and give examples. Explain the benefits and risks of selective breeding in plants and animals. 1 Images of different dogs. Students ‘breed’ and name a new dog from selecting any 2 – draw a picture of their new breed. Draw a flow diagram to explain the steps involved in selective breeding. Give examples of characteristics that are selectively bred in plants and animals. Discuss the advantages and of selective breeding in plants and animals. Debate: Should people be allowed to breed dogs? Produce a model to describe selective breeding. Consider the social, economic and ethical implications of selective breeding. clips:
produce more milk, animals that produce more, better flavoured or leaner meat. Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects. Some breeds of dogs suffer from inbred defects. 4.6.2.2 Evolution Darwin’s theory of evolution by natural selection states that all species evolved from simple life forms that first developed more than three billion years ago. The main stages of natural selection. Describe Darwin’s theory of evolution by natural selection. Describe the main stages of natural selection as: individual organisms within a particular species may show a wide range of phenotype variation because of differences in their genes individuals with characteristics most 2 Look at exhibition to show the wide variety of organisms that live, or have lived, on Earth. Discuss how they were all formed. BBC activity Evolution. Watch BBC video clip illustrating survival of the fittest (see resources). Watch video clip about ancestor of horses from BBC Walking with Beasts. Use a model to explain natural selection. Video clip Horse ancestor: Darwin and evidence for evolution; extinction:
4.6.2.2 Mutations are changes in the DNA code. They may lead to more rapid evolution, although mutations that result in a new phenotype are rare. Organisms of the same species can interbreed to produce fertile offspring. suited to the environment are more likely to survive to breed successfully the genes that have enabled these individuals to survive are then passed on to the next generation. Define the term mutation. Explain why mutation may lead to more rapid change in a species. Define the term species. Identify organisms that are of different species. Interpret evolutionary trees. Draw a flow diagram to explain natural selection. Natural selection role play activities. Peppered moth game; explain in terms of natural selection. Look at pictures of Darwin’s finches and match up with the Galapagos Island they lived on based on food available there. Discuss how you show that a donkey and a horse are different species. Interpret evolutionary trees. Describe how to gather evidence for an evolutionary tree to describe relationships between organisms. Include the time scales involved in evolution. 4.6.3.1 4.6.3.2 4.6.3.4 Evidence for evolution – Fossils and Resistant bacteria. The theory of evolution by natural selection is now widely accepted. Describe the evidence for the theory of evolution by natural selection. Define the term ‘fossil’. Describe how fossils may be formed: 1 Discuss the evidence we have to support Darwin’s theory and present in a suitable format. Observe fossils or pictures of fossils. Draw fossils. Fossils and pictures of fossils. Fossil formation:
4.6.3.1 4.6.3.2 4.6.3.4 Resistant bacteria Bacteria can evolve rapidly because they reproduce at a fast rate. Mutations produce new strains. Resistant strains are not killed by antibiotics, so they survive and reproduce. Resistant strains spread because people are not immune and there is no effective treatment. MRSA is resistant to antibiotics. How to reduce the development of resistant strains. Problems associated with the Explain what we should do to slow down the rate of development of resistant strains of bacteria. Describe the impact of antibiotic resistance. Explain how bacteria can become resistant to antibiotics. Explain how antibiotic resistance has impacted on cleaning practices in Britain’s hospitals. Interpret data about antibiotic resistance. Role play: life without antibiotics. Research MRSA and C. difficile infections and treatment. Discuss how the rate of development of resistant bacteria be slowed down. Discuss why there are few new antibiotics being developed, and suggest how drug companies might be encouraged to develop some.