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6. Inheritance, variation and evolution

Reproduction

2 lessons
6.1 Sexual and asexual reproduction How sexual reproduction (gametes, fertilisation, variation) differs from asexual reproduction (one parent, mitosis, clones), the advantages and disadvantages of each, and organisms that can reproduce both ways. AQA Edexcel OCR 6.2 Meiosis How meiosis in the reproductive organs halves the chromosome number to make four genetically different gametes, how fertilisation restores the full number, and the difference between haploid and diploid cells. AQA Edexcel OCR

DNA and protein synthesis

4 lessons
6.3 DNA and the genome DNA as a polymer of two strands in a double helix, nucleotides and complementary base pairs (A-T, C-G), how DNA is packed into chromosomes, genes as sections of DNA that code for proteins, and the genome. AQA Edexcel OCR 6.4 Extracting DNA from fruit Edexcel: how to extract DNA from fruit such as strawberries using detergent, salt, filtering, protease and ice-cold ethanol, and why each step is needed. Edexcel 6.5 Protein synthesis How the base sequence of a gene codes for a protein: the triplet code, transcription of DNA into mRNA in the nucleus, translation at the ribosome with carrier molecules (tRNA), and folding of the amino acid chain into a protein. Higher only Separate only AQA Edexcel OCR 6.6 Mutations and genetic variants What mutations are, why most have no effect on the protein, how a change in a coding region can change the shape of a protein such as an enzyme, and how variants in non-coding DNA can switch genes on or off. Higher only AQA Edexcel OCR

Genetic inheritance

6 lessons
6.7 Genetic terms and monohybrid crosses The key terms of genetics (allele, dominant, recessive, homozygous, heterozygous, genotype, phenotype), how to draw Punnett squares for single-gene crosses, work out ratios and probabilities, and read family trees. AQA Edexcel OCR 6.8 Inherited disorders and embryo screening AQA: polydactyly (caused by a dominant allele) and cystic fibrosis (caused by a recessive allele), working out the chance of a child inheriting them, embryo screening, and the economic, social and ethical issues it raises. AQA 6.9 Sex determination How sex is decided by the sex chromosomes (XX female, XY male), a genetic diagram showing why there is a 50% chance of a boy or a girl, and why the father's sperm decides the sex of the child. AQA Edexcel OCR 6.10 Blood groups and sex-linked disorders Edexcel: inheritance of the ABO blood groups with multiple alleles and codominance, and sex-linked inheritance of red-green colour blindness and haemophilia on the X chromosome, including why males are more often affected. Separate only Edexcel 6.11 Mendel and our understanding of genetics Gregor Mendel's breeding experiments with pea plants, the 3:1 ratio and his idea of inherited 'units', why his work was not recognised for decades, and how the discovery of chromosomes, genes and DNA built on it. Separate only AQA Edexcel OCR 6.12 The Human Genome Project Edexcel and OCR: what the Human Genome Project achieved, how knowing the human genome is used in medicine (finding disease alleles, genetic testing, personalised drugs), and the problems and ethical concerns it raises. Edexcel OCR

Variation and evolution

6 lessons
6.13 Variation The causes of variation (genes, the environment, or both), continuous and discontinuous variation and how to show them on graphs, and how mutations create new genetic variants. AQA Edexcel OCR 6.14 Evolution by natural selection The theory of evolution by natural selection: variation, competition, survival of the best adapted, reproduction and inheritance of alleles over many generations, with the peppered moth as an example, and how new species form. AQA Edexcel OCR 6.15 Darwin, Wallace and speciation Darwin's observations and his theory of evolution by natural selection, why it was slow to be accepted, Lamarck's rejected idea, Alfred Russel Wallace's contribution, and how geographical isolation leads to new species (speciation). Separate only AQA Edexcel OCR 6.16 Evidence for evolution: fossils and resistant bacteria How fossils form (in places where decay cannot happen, by mineral replacement, or as traces), why the fossil record is incomplete, and how antibiotic-resistant bacteria such as MRSA show evolution happening now. AQA Edexcel OCR 6.17 Extinction AQA: what extinction is and its causes, including new predators, new diseases, more successful competitors, catastrophic events and changes to the environment over time, with examples. AQA 6.18 Human evolution: fossils and stone tools Edexcel: fossil evidence for human evolution (Ardi, Lucy and Leakey's Turkana Boy), how stone tools developed and are dated, and (Biology only) the pentadactyl limb as evidence for evolution. Edexcel

Breeding and genetic engineering

3 lessons
6.19 Selective breeding How humans breed plants and animals for particular characteristics over many generations, examples such as disease-resistant crops, high-yield animals, gentle dogs and large flowers, and the risks of inbreeding. AQA Edexcel OCR 6.20 Genetic engineering How genes are cut from one organism and inserted into another using enzymes and vectors, examples such as bacteria making human insulin and GM crops, and the benefits and risks of genetic engineering in farming and medicine. AQA Edexcel OCR 6.21 Cloning plants and animals How plants are cloned by cuttings and tissue culture, and animals by embryo transplants and adult cell cloning (as with Dolly the sheep), with the uses, benefits and risks of cloning. Separate only AQA Edexcel

Classification

1 lesson
6.22 Classification and the three domains How living things are classified: Linnaeus's system of kingdom, phylum, class, order, family, genus and species, binomial names, evolutionary trees, and Carl Woese's three-domain system based on genetic analysis. AQA Edexcel OCR