This clear and concise lesson describes the meaning of a gene locus and explains how the inheritance of two or more genes that have loci on the same chromosome demonstrates linkage. The engaging PowerPoint and associated resource have been designed to cover points 3.9 (i) and (ii) of the Edexcel International A-level Biology specification and makes clear links to the upcoming topic of meiosis when describing the effect of crossing over on this linkage
This is a topic which can cause confusion for students so time was taken in the design to split the concept into small chunks. There is a clear focus on how the number of original phenotypes and recombinants can be used to determine linkage and suggest how the loci of the two genes compare. Important links to other topics such as crossing over in meiosis are made to enable students to understand how the random formation of the chiasma determines whether new phenotypes will be seen in the offspring or not. Linkage is an important cause of variation and the difference between observed and expected results and this is emphasised on a number of occasions. The main task of the lesson acts as an understanding check where students are challenged to analyse a set of results involving the inheritance of the ABO blood group gene and the nail-patella syndrome gene to determine whether they have loci on the same chromosome and if so, how close their loci would appear to be.
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Topic 3: Cell structure, Reproduction & Development (Edexcel International A-level Biology)
The locus and linkage, meiosis, differential gene expression and protein transport within cells lessons have been uploaded for free and by downloading these, you will be able to observe the detail of planning that has gone into all of the lessons that are included in this bundle. This intricate planning ensures that the students are engaged and motivated whilst the detailed content of topic 3 (Cell structure, Reproduction and Development) of the Edexcel International A-level Biology specification is covered. The 14 lesson PowerPoints and accompanying resources contain a wide range of activities which cover the following topic 3 specification points: * All living organisms are made of cells * Cells of multicellular organisms are organised into tissues, organs and organ systems * The ultrastructure of eukaryotic cells * The function of the organelles in eukaryotic animal cells * The role of the RER and Golgi apparatus in protein transport within cells * The ultrastructure of prokaryotic cells * Magnification and resolution in light and electron microscopes * The gene locus is the location of a gene on a chromosome * The linkage of genes on a chromosome * The role of meiosis in ensuring genetic variation * Understand how the mammalian gametes are specialised for their functions * The role of mitosis and the cell cycle in growth and asexual reproduction * Calculation of mitotic indices * The meaning of the terms stem cell, pluripotent, totipotent, morula and blastocyst * The decisions that have to be made about the use of stem cells in medical therapies * Cells become specialised through differential gene expression * One gene can give rise to more than one protein through post-transcriptional changes to mRNA * Phenotype is the interaction between genotype and the environment * Epigenetic modifications can alter the activation of certain genes * Some phenotypes are affected by multiple alleles or by polygenic inheritance Due to the detail included in all of these lessons, it is estimated that it will take in excess of 6 weeks of allocated A-level teaching time to complete the teaching of the bundle
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DNA, RNA, Genetics and Inheritance (Edexcel Int. A-level Biology)
This lesson bundle contains 16 lessons which have been designed to cover the Edexcel International A-level Biology specification points which focus on the structure of DNA and RNA, their roles in replication and protein synthesis, and genetics and inheritance. The lesson PowerPoints are highly detailed, and along with their accompanying worksheets, they have been planned at length to contain a wide range of engaging tasks which cover the following A-level Biology content found in topics 2, 3 and 6 of the course: 2.9 (i): Know the basic structure of mononucleotides (deoxyribose or ribose linked to a phosphate and a base, including thymine, uracil, adenine, cytosine or guanine) and the structures of DNA and RNA (polynucleotides composed of mononucleotides linked by condensation reactions to form phosphodiester bonds) 2.9 (ii): Know how complementary base pairing and the hydrogen bonding between two complementary strands are involved in the formation of the DNA double helix 2.10 (i): Understand the process of DNA replication, including the role of DNA polymerase 2.11: Understand the nature of the genetic code 2.12: Know that a gene is a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain 2.13 (i): understand the process of protein synthesis (transcription and translation), including the role of RNA polymerase, translation, messenger RNA, transfer RNA, ribosomes and the role of start and stop codons 2.13 (ii): Understand the roles of the DNA template (antisense) strand in transcription, codons on messenger RNA and anticodons on transfer RNA 2.14 (i): Understand how errors in DNA replication can give rise to mutations (substitution, insertion and deletion of bases) 2.14 (ii): Know that some mutations will give rise to cancer or genetic disorders, but that many mutations will have no observable effect 2.15 (i): Know the meaning of the terms: gene, allele, genotype, phenotype, recessive, dominant, codominance, homozygote and heterozygote 2.15 (ii): Understand patterns of inheritance, including the interpretation of genetic pedigree diagrams, in the context of monohybrid inheritance 2.15 (iii): Understand sex linkage on the X chromosome, including red-green colour blindness in humans 2.16: Understand how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and reproductive systems 2.17 (i): Understand the uses of genetic screening, including the identification of carriers, pre-implantation genetic diagnosis (PGD) and prenatal testing, including amniocentesis and chorionic villus sampling 2.17 (ii): Understand the implications of prenatal genetic screening 3.9 (i): Know that a locus is the location of genes on a chromosome 3.9 (ii): Understand the linkage of genes on a chromosome 3.18: Understand how cells become specialised through differential gene expression, producing active mRNA, leading to the synthesis of proteins which, in turn, control cell processes or determine cell structure in animals and plants 3.19: Understand how one gene can give rise to more than one protein through posttranscriptional changes to messenger RNA (mRNA). 3.20 (i): Phenotype is an interaction between genotype and the environment 3.21: Understand how some phenotypes are affected by multiple alleles for the same gene at many loci (polygenic inheritance) as well as the environment and how this can give rise to phenotypes that show continuous variation 6.17: Know how DNA can be amplified using the polymerase chain reaction (PCR)
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