Genetics

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Learning objectives Possible learning and teaching activities Expected learning outcomes

Students should learn Students should be able to

3.1.1 Nature and action of the gene

 the structure and chemical nature of DNA to show its role as the genetic material. [Refer to Section 1.1.4.]

 Use models or audiovisual materials to illustrate the double helical structure of DNA.

 Construct simple models of DNA using common materials (e.g. poppit beads, plasticine, cardboard, wire, pipe cleaners).

 Extract DNA (e.g. DNA spooling) using living materials.

 state the role of DNA.

 relate the structure of DNA to its role as the genetic material.

 the semiconservative nature of DNA replication:

mechanism and evidence as illustrated by the work of Meselson and Stahl.

 Use models or audiovisual materials to illustrate the semiconservative mechanism of DNA replication.

 appreciate the process involved in scientific investigation.

 the features of the genetic code.  Discuss with students how to use three letters to construct a large number of words.

 state the features of the genetic code.

 the roles of DNA and RNAs in protein synthesis.  Use models or audiovisual materials to demonstrate the roles of DNA and RNAs in protein synthesis.

 describe the process of protein synthesis.

 explain how genes determine body characteristics.

 Construct more complex models of a section of DNA and a complementary mRNA molecule (e.g.

using commercial kits).

 that genes can be turned on and off.  realise that genes can be turned on and off.

3.1.2 Structure of chromosomes

 the organisation of DNA into chromosomes in eukaryotic cells.

 Observe giant chromosomes (e.g. the salivary glands of Chironomus larvae) in squashed preparations or photomicrographs.

 distinguish between DNA and chromosomes.

3.1.3 Cell cycle

 interphase: duplication of DNA

 nuclear division

(1) Mitosis : behaviour of chromosomes at prophase, metaphase, anaphase and telophase; the significance of mitosis.

 Observe and identify the different stages of mitosis using squashed tissues, prepared slides, or photomicrographs of root tip.

 describe the process of mitosis.

 identify the different stages of mitosis.

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Learning objectives Possible learning and teaching activities Expected learning outcomes

Students should learn Students should be able to

(2) Meiosis : behaviour of chromosomes during first and second divisions of meiosis including chiasma formation; crossing over;

the significance of meiosis.

 Observe meiosis in plant and animal cells using prepared slides or photomicrographs.

 describe the process of meiosis.

 compare the processes of mitosis and meiosis.

 state and explain the significance of mitosis and meiosis.

 an outline of cytoplasmic division in animal and plant cells.

 point out that cell cycle consists of interphase, nuclear division and cytoplasmic division.

3.1.4 Inheritance of discrete characters

 monohybrid and dihybrid crosses. (The pioneer work of Mendel should be referred to.)

 backcross and test cross.

 dominance and recessiveness.

 Incomplete dominance (e.g. the colour of petals in snapdragon).

 codominance (e.g. human blood group AB).

 multiple alleles (e.g. human ABO blood groups).

 sex-linked traits (e.g. haemophilia and red-green colour blindness).

 Discuss how Mendel conceived his theories on the basis of empirical evidence.

 Study the results of monohybrid and dihybrid crosses to illustrate the patterns of inheritance.

 Use computer simulation to study genetic crosses of some organisms (e.g. Drosophila).

 Construct a pedigree of the inheritance of some human traits (e.g. ABO blood groups, tongue rolling, ear lobe of the family).

 Use chi-square test to estimate the matching between observed and expected phenotypic outcomes.

 Provide genetic problem to guide students to interpret and predict the results of genetic crosses.

 appreciate the importance of imagination and evidence in the formulation of hypotheses.

 explain and predict inheritance patterns in monohybrid and dihybrid crosses.

 state the use of backcross and test cross.

 predict the possible phenotypes of the offspring in genetic cross.

 state different patterns of inheritance from results of genetic crosses.

 linkage and crossing over.  relate linkage of genes and crossing over to

chromosomal behaviour during meiosis.

 state the significance of crossing over.

3.1.5 Discontinuous and continuous variations

 the factors contributing to variations between individuals within a species.

 discontinuous variations (e.g. tongue rolling and ABO blood groups in humans) and continuous variations (e.g. height and weight in humans).

 realise that variations occur.

 explain how mutation, meiosis and fertilisation may lead to genetic variations.

 evaluate the importance of genetic factors and environmental factors in causing variations.

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Learning objectives Possible learning and teaching activities Expected learning outcomes

Students should learn Students should be able to

 the normal distribution curve.

 the use of standard deviation as a measure of the variation of a sample.

 Collect and analyse data on continuous and discontinuous variations using appropriate statistical software.

 demonstrate statistical skills in data analysis.

 the outline of polygenic inheritance and the effects of environment on it.

 outline polygenic inheritance.

 state the effects of environment on phenotypes.

3.1.6 Mutation

 gene mutation: the effect of gene mutation on amino acid sequence (e.g. sickle-cell anaemia).

 chromosome mutation: changes in chromosome structure and chromosome number (e.g. Down syndrome).

 Display pictures showing the symptoms of some diseases caused by gene mutation and

chromosome mutation.

 Show photomicrographs of karyotypes of chromosome mutation.

 point out that mutation can take place at different levels.

 the types of mutation: spontaneous and induced mutations.

 that mutations can be enhanced by ionising radiations and chemicals. [Refer to Section 6.]

 Use available evidence to assess the nature of risks involved in exposure to mutagens.

 Discuss the precautionary measures in using X-ray in medical examination.

 Search for information on the sources of mutagenic agents and their effects on human health.

 state the different causes of mutation.

 practise ways to minimise the risk of developing mutation.

 develop a concern for the proliferation of mutagenic agents.

 significance of mutation.  explain the importance of mutation in the

mechanism of evolution.

3.1.7 Applications of genetics

 human genetics:

(1) Pedigree analysis (e.g. colour blindness).  Analyse pedigrees to trace the inheritance of some human traits.

 apply the principles of genetics in pedigree analysis.

(2) Genetic screening (e.g. detection of Down syndrome).

 Search for information on the kinds of genetic diseases that can be detected by screening test.

 appreciate the use of genetic screening in detecting some genetic diseases.

 Conduct a small survey or project on the available screening services for the detection of common genetic diseases in Hong Kong.

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Learning objectives Possible learning and teaching activities Expected learning outcomes

Students should learn Students should be able to

(3) Prenatal and postnatal counselling of genetic diseases (e.g. glucose6phosphate

dehydrogenase deficiency and thalassaemia).

 Search for information on the provision of prenatal and postnatal counselling of genetic diseases in Hong Kong.

 Visit a prenatal and postnatal genetic counselling check-up clinic.

 develop an awareness of the importance of genetic counselling.

(4) Gene therapy as a potential treatment of genetic diseases (e.g. cystic fibrosis).

 Search for information on examples of gene therapy and the prospects of gene therapy in relation to the Human Genome Project.

 appreciate the potential use of gene therapy.

(5) The implications of the Human Genome Project.

 Debate on the pros and cons of the Human Genome Project (HGP) or discuss the ethical and social concerns brought about by the HGP.

 discuss the contributions and concerns of the findings of the Human Genome Project.

 plant and animal breeding

(1) Artificial selection and breeding for selected traits to produce desirable varieties. Hybrid vigour and polyploidy.

 Use audiovisual materials to show artificial insemination and cloning.

 Search for information on selective plant breeding, e.g. miracle rice.

 Search for information on modern technological advances in the selective breeding of domestic animals, e.g. the use of sperm banks, artificial insemination, and embryo transplants.

 appreciate the application of making appropriate genetic crosses to produce progeny with desirable traits.

 explain the biological principles behind artificial selection.

(2) Cloning. [Refer to Section 12.]  Read about tissue culture in plant cloning, e.g.

orchid.

 Search for information on animal cloning.

 appreciate the application of cloning in

maintaining desirable traits in selected plants and animals.

 the outline of the principle of recombinant DNA technology and its applications.

 Use diagrams or flow charts to illustrate the principle of recombinant DNA technology.

 outline the principle of recombinant DNA technology.

 cite examples of the applications of recombinant DNA technology.

 the outline of the principle of DNA fingerprinting, and its forensic use, e.g. parentage test.

 Carry out separation of DNA or polypeptides by electrophoresis.

 Use audiovisual materials to illustrate the process of DNA fingerprinting.

 outline the principle of DNA fingerprinting.

 state the applications of DNA fingerprinting.

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Learning objectives Possible learning and teaching activities Expected learning outcomes

Students should learn Students should be able to

 Examine cases or discuss the use of DNA fingerprinting in forensic science.

 implications of genetic manipulation: the potential benefits, hazards and ethical issues.

 Debate on the pros and cons of genetic engineering or genetically modified food.

 discuss potential benefits, hazards and ethical issues related to genetic manipulation.

 appreciate that genetic engineering has made possible the development of new biotechnologies and careers.

在文檔中 Membership of the CDC Ad Hoc Committee on the Development of A-Level Biology Curriculum (頁 36-41)