4th Sep '25

Schemes of Work

B2
- B2.3
  - Lesson 01 - What is a genome? Lesson Plan Lesson Title
    - Students should be able to describe the structure of DNA and define genome.
    - The genetic material in the nucleus of a cell is composed of a chemical called DNA.
    - DNA is a polymer made up of two strands forming a double helix.
    - The DNA is contained in structures called chromosomes.
    - The genome of an organism is the entire genetic material of that organism.
      - Suggested Activity:
        Extracting DNA from fruit
        
        https://www.nuffieldfoundation.org/practical-biology/extracting-dna-living-things
        Equipment Required:
        smashed up fruit
        extracting solution pre made
        ice cold ethanol
        steralised boiling tubes
        pipettes
    - The whole human genome has now been studied and this will have great importance for medicine in the future.
    - Students should be able to discuss the importance of understanding the human genome.
    - Each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to the sugar
    - A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein.
      - Suggested Activity:
        https://www.youtube.com/watch?v=hywRdDVR76A
        
        Sort the order into: Nucleotide, Gene, Chromosome, Genome.
        Explain why the order of the bases is important.
        
        Higher:
        
        https://www.youtube.com/watch?v=zwibgNGe4aY
        
        (first 3 minutes)
        Describe how a gene leads to a protein.
        Explain why a base change could change the properties of a protein.
    - This is limited to the:
      - search for genes linked to different types of disease
      - understanding and treatment of inherited disorders
      - use in tracing human migration patterns from the past.
      - Suggested Activity:
        EW: Evaluate the research into the human genome against the cost the of the project and the on-going research into what the genes do.
        https://www.genome.gov/27565109/the-cost-of-sequencing-a-human-genome/
        
        GF: Was cooperation or competition more important in achieving the human genome project? https://www.youtube.com/watch?v=AhsIF-cmoQQ
    - DNA contains four bases, A, C, G and T.
  - Lesson 02 - What does the genetic code do? Lesson Plan Lesson Title
    - Students should be able to describe DNA as a polymer made from four different nucleotides.
    - A sequence of three bases is the code for a particular amino acid.
    - The order of bases controls the order in which amino acids are assembled to produce a particular protein.
      - Suggested Activity:
        Give possible codons for the 24 amino acids. Produce base sequence (in multiples of 3) (ending in stop codon).
        
        Extension - propose changes to base sequence, some that have no effect on amino acid sequence, so that would cause a point mutation and the effects of an insertion or deletion. Get them to comment on the significance of each mutation.
    - The long strands of DNA consist of alternating sugar and phosphate sections. Attached to each sugar is one of the four bases
    - The DNA polymer is made up of repeating nucleotide units. Interpret a diagram of DNA structure but will not be required to reproduce it.
    - (HT only) Students should be able to recall a simple description of protein synthesis
    - explain simply how the structure of DNA affects the protein made
    - describe how genetic variants may influence phenotype: a) in coding DNA by altering the activity of a protein: and b) in non-coding DNA by altering how genes are expressed
    - (HT only) In the complementary strands a C is always linked to a G on the opposite strand and a T to an A.
    - (HT only) Students are not expected to know or understand the structure of mRNA, tRNA, or the detailed structure of amino acids or proteins.
    - (HT only) Students should be able to explain how a change in DNA structure may result in a change in the protein synthesised by a gene
    - (HT only) Proteins are synthesised on ribosomes, according to a template.
    - (HT only) Carrier molecules bring specific amino acids to add to the growing protein chain in the correct order
    - (HT only) When the protein chain is complete it folds up to form a unique shape. This unique shape enables the proteins to do their job as enzymes, hormones or forming structures in the body such as collagen.
      - Suggested Activity:
        Separates Only: Storyboard / flow chart / stop-frame animation of the process of protein synthesis.
        GF: Explain how a change in base sequence can lead to a change in properties of a protein, linked to the shape of the protein.
  - Lesson 03 - How does meiosis produce gametes? Lesson Plan Lesson Title
    - Students should be able to explain how meiosis halves the number of
      chromosomes in gametes and fertilisation restores the full number of chromosomes.
    - Cells in reproductive organs divide by meiosis to form gametes.
    - When a cell divides to form gametes:
      ? copies of the genetic information are made
      ? the cell divides twice to form four gametes, each with a single 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. The number of cells
      increases. As the embryo develops cells differentiate.
      - Suggested Activity:
        Pipe cleaner chromosomes (possibly take photo of each stage as they divide) and follow from duplicating the pipe cleaner chromosomes and following the path of division to end of with 4 haploid cells.
        Double Bubble mitosis division with meiosis division (similar - replicate and line up along middle, differences - how they line up along the middle and the number of divisions).
        GF: Explain how meiosis creates variation in the way it divides and why this is important.
    - Knowledge of the stages of meiosis is not required
  - Lesson 04 - How are sexual and asexual reproduction different? Lesson Plan Lesson Title
    - Meiosis leads to non-identical cells being formed
    - Mitosis leads to identical cells being formed.
    - Sexual reproduction involves the joining (fusion) of male and female gametes:
      ? sperm and egg cells in animals
      ? pollen and egg cells in flowering plants.
    - In sexual reproduction there is mixing of genetic information which leads to variety in the offspring.
    - The formation of gametes involves meiosis.
    - Asexual reproduction involves only one parent and no fusion of gametes.
    - (HT only) Mutations occur continuously. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.
    - (HT only) A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
    - (HT only) Modelling insertions and deletions in chromosomes to illustrate mutations
    - (HT only) A few mutations code for an altered protein with a different shape. An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength.
    - There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved.
      - Suggested Activity:
        Table comparing the products of meiosis to mitosis. (Number of divisions, number of cells formed, haploid or diploid, unique or identical, purpose of division)
        Table comparing sexual and asexual reproduction. (number of parents, fusion of gametes, clone or unique, faster or slower, creates variation or not)
        EW (Not for separates as they have other content to cover and can complete this activity in a future lesson) Describe the lifecycle of the aphid and describe how it carries out both asexual and sexual reproduction.
    - (HT only) Not all parts of DNA code for proteins. Non-coding parts of DNA can switch genes on and off, so variations in these areas of DNA may affect how genes are expressed.
      - Suggested Activity:
        Evaluate the effects of mutations to the genetic code.
        Bar headed goose and haemoglobin with higher affinity for oxygen allows it to fly over mountain range on migration rather than around like other geese species.
        Sickle Cell Anaemia - negative effects of mutation and also positive effect for malaria resistance.
        Neutral mutations - eye colour.
  - Lesson 05 - Why do some species carry out asexual and sexual reproduction? Lesson Plan Lesson Title
    - Knowledge of reproduction in organisms is restricted to those mentioned
    - Students are expected to be able to explain the advantages and
      disadvantages of asexual and sexual reproduction for any organism if given appropriate information.
      - Suggested Activity:
        Research task: Malarial parasite (plasmodium), fungi such mushrooms and plants - strawberry plants and daffodils.
        Describe how these species reproduce both sexually and asexually.
    - Examples of organisms reproducing by both methods includes: ? Malarial parasites reproduce asexually in the human host, but sexually in
      the mosquito.
      ? Many fungi reproduce asexually by spores but also reproduce sexually to give variation.
      ? Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils.
      Historical developments of our understanding of the causes and prevention of malaria. (WS)
    - Advantages of sexual reproduction:
      ? produces variation in the offspring
      ? if the environment changes variation gives a survival advantage by natural selection
      ? natural selection can be speeded up by humans in selective breeding to increase food production.
    - Advantages of asexual reproduction:
      ? only one parent needed
      ? more time and energy efficient as do not need to find a mate
      ? faster than sexual reproduction
      ? many identical offspring can be produced when conditions are favourable.
      - Suggested Activity:
        Separates only - Think Pair Share - suggestions of the advantages and disadvantages of both reproductive strategies. Question about which strategies suit animals depending on how long they live/how long the offspring are cared for.
    - Some organisms reproduce by both methods depending on the
      circumstances.
      - Suggested Activity:
        Separates only - EW Compare the use of asexual and sexual reproduction as strategies for the aphid (asexual of successful individuals in the summer when resources are plentiful, sexual for the next year to introduce variation for what may be different conditions next year)
        GF: Suggest how this life cycle strategy could have evolved.
  - Lesson 06 - How can the chance of a characteristic being passed on be predicted? Lesson Plan Lesson Title
    - Students should be able to explain the term chromosome
    - Students should be able to explain the term gene
    - Students should be able to explain the term allele
    - Students should be able to explain the term dominant
    - Students should be able to explain the term recessive
    - Students should be able to explain the term homozygous
    - Students should be able to explain the term hetrozygous
    - Students should be able to explain the term genotype
    - Students should be able to explain the term phenotype
    - Some characteristics are controlled by a single gene, such as: fur colour in mice; and red-green colour blindness in humans. Each gene may have different forms called alleles.
    - The alleles present, or genotype, operate at a molecular level to develop characteristics that can be expressed as a phenotype.
    - A dominant allele is always expressed, even if only one copy is present.
    - A recessive allele is only expressed if two copies are present (therefore no dominant allele present).
    - If the two alleles present are the same the organism is homozygous for that trait, but if the alleles are different they are heterozygous.
    - Most characteristics are a result of multiple genes interacting, rather than a single gene.
    - Students should be able to understand the concept of probability in predicting the results of a single gene cross, but recall that most phenotype features are the result of multiple genes rather than single gene inheritance
    - Students should be able to use direct proportion and simple ratios to express the outcome of a genetic cross.
    - Students should be able to complete a Punnett square diagram and extract and interpret information from genetic crosses and family trees.
    - (HT only) Students should be able to construct a genetic cross by Punnett square diagram and use it to make predictions using the theory of probability
      - Suggested Activity:
        Complete Punnett squares. Identify incorrect Punnett squares, calculate the chances and ratios from a Punnett square.
        (decent worksheet in B2.3 folder)
        HT - give questions about crosses and get pupils to construct Punnett or work backwards to find phenotypes of parents.
  - Lesson 07 - How are some disorders inherited? Lesson Plan Lesson Title
    - Some disorders are inherited. These disorders are caused by the
      inheritance of certain alleles.
    - Polydactyly (having extra fingers or toes) is caused by a dominant allele.
    - Cystic fibrosis (a respitory disease) is caused by a recessive allele, so both parents must carry the gene in order for the offspring to have the disease.
      - Suggested Activity:
        Compare (possibly in a table) the mutation, it's effects, whether it is dominant or recessive and the combinations from the parents by which it would be inherited.
        
        Use pedigree charts to work out family history of inherited conditions. Maybe Haemophilia and the Royal family as an example.
    - Students should make informed judgements about the economic, social and ethical issues concerning embryo screening, given appropriate information. Appreciate that embryo screening and gene therapy may alleviate suffering but consider the ethical issues which arise.
      - Suggested Activity:
        EW: Evaluate whether embryo screening is the 'right thing' to do.
    - Ordinary human body cells contain 23 pairs of chromosomes.
    - 22 pairs control characteristics only, but one of the pairs carries the genes that determine sex.
    - ? In females the sex chromosomes are the same (XX).
      ? In males the chromosomes are different (XY).
    - Students should be able to carry out a genetic cross to show sex inheritance.
    - Students should understand and use direct proportion and simple ratios in genetic crosses.
      - Suggested Activity:
        Complete Punnett squares to demonstrate there is a 50:50 chance of having a girl or a boy.