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SINGAPORE-CAMBRIDGE GCE A-LEVEL

BIOLOGY OUTLINE (H2)

SYLLABUS 9648

UPDATED 5 FEB 2014

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Overview

Themes Chapters Count

I. How Life Works 1-6 6

II. Understanding the Diversity of Organisms

7 1

III. Relevance to Oneself and Society 8-9 2

A. CORE SYLLABUS........................................................................................................................9

1. Cellular Functions..........................................................................................................................9

2. DNA and Genomics.....................................................................................................................11

3. Genetics of Viruses and Bacteria.................................................................................................12

4. Organisation and Control of Prokaryotic and Eukaryotic Genomes.............................................13

5. Genetic Basis for Variation...........................................................................................................14

6. Cellular Physiology and Biochemistry..........................................................................................15

7. Diversity and Evolution.................................................................................................................17

B. APPLICATIONS SYLLABUS.....................................................................................................19

8. Isolating, Cloning and Sequencing DNA......................................................................................19

9. Applications of Molecular and Cell Biology..................................................................................20

2 Compiled by Lim Ting Jie

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Contents

A. CORE SYLLABUS........................................................................................................................9

1. Cellular Functions........................................................................................................................9

(a) Describe and interpret drawings and photographs of typical animal and plant cells as seen under the electron microscope, recognising the following membrane systems and organelles: rough and smooth endoplasmic reticulum, Golgi body, mitochondria, ribosomes, lysosomes, chloroplasts, cell surface membrane, nuclear envelope, centrioles, nucleus and nucleolus. (Knowledge of the principles of TEM and SEM are not required.) (For practical assessment, students may be required to operate a light microscope, mount slides and use a graticule.)........9

(b) Outline the functions of the membrane systems and organelles listed in (a)............................9

(c) Describe the formation and breakage of a glycosidic bond.......................................................9

(d) Analyse the molecular structure of a triglyceride and a phospholipid, and relate these structures to their functions in living organisms..............................................................................9

(e) Describe the structure of an amino acid and the formation and breakage of a peptide bond...9

(f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape..................................................9

(g) Analyse the molecular structure of a protein with a quaternary structure e.g. haemoglobin, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions...................................................................................................9

(h) Explain the mode of action of enzymes in terms of an active site, enzyme/substrate complex, lowering of activation energy and enzyme specificity.....................................................................9

(i) Follow the time course of an enzyme-catalysed reaction by measuring rates of formation of products (e.g. using catalase) or rate of disappearance of substrate (e.g. using amylase)...........9

(j) Investigate and explain the effects of temperature, pH, enzyme concentration and substrate concentration on the rate of enzyme catalysed reactions, and explain these effects..................10

(k) Explain the effects of competitive and non-competitive inhibitors (including allosteric inhibitors) on the rate of enzyme activity......................................................................................10

(l) Explain the importance of mitosis in growth, repair and asexual reproduction........................10

(m) Explain the need for the production of genetically identical cells and fine control of replication.....................................................................................................................................10

(n) Explain how uncontrolled cell division can result in cancer, and identify causative factors (e.g. genetic, chemical carcinogens, radiation, loss of immunity) which can increase the chances of cancerous growth. (Knowledge that dysregulation of checkpoints of cell division can result in uncontrolled cell division and cancer is required, but detail of the mechanism is not required.)..10

(o) Describe with the aid of diagrams, the behaviour of chromosomes during the mitotic cell cycle and the associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected).....................................................................................................10

(p) Explain what is meant by homologous pairs of chromosomes...............................................10

(q) Explain the need for reduction division (meiosis) prior to fertilisation in sexual reproduction. 10

(r) Explain how meiosis and random fertilisation can lead to variation.........................................10


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(s) Describe, with the aid of diagrams, the behaviour of chromosomes during meiosis, and the associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected, but not the sub-divisions of prophase)..............................................10

2. DNA and Genomics....................................................................................................................11

(a) Describe the structure and roles of DNA and RNA (tRNA, rRNA and mRNA). (Mitochondrial DNA is not required.)....................................................................................................................11

(b) Describe the process of DNA replication and the experimental evidence for semi-conservative replication................................................................................................................11

(c) Describe how the information on DNA is used to synthesise polypeptides in prokaryotes and eukaryotes. (Description of the processes of transcription, formation of mRNA from pre-mRNA and translation is required.)..........................................................................................................11

(d) Explain how a change in the sequence of the DNA nucleotide (gene mutation) may affect the amino acid sequence in a protein, and hence the phenotype of the organism e.g. sickle cell anaemia and cystic fibrosis. (Knowledge of substitution, addition, deletion and frameshift mutation may be required.)...........................................................................................................11

3. Genetics of Viruses and Bacteria.............................................................................................12

(a) Discuss whether viruses are living or non-living organisms and explain why viruses are obligate parasites.........................................................................................................................12

(b) Describe the structural components of viruses.......................................................................12

(c) Describe the reproductive cycles of the following virus types: i. bacteriophages that reproduce via a lytic cycle, e.g. T4 phage; ii. bacteriophages that reproduce via a lysogenic cycle, e.g. lambda phage; iii. an enveloped virus e.g. influenza; iv. retroviruses e.g. HIV............................12

(d) Explain how viral infections cause disease in animals, e.g. mammals, through the disruption of host tissue and functions (e.g. HIV and T helper cells [details of the immune system are not required], influenza and epithelial cells of the respiratory tract)...................................................12

(e) Describe the structure of a bacterial chromosome including the arrangement of DNA within bacterial cells................................................................................................................................12

(f) Describe the process of binary fission, transformation, transduction and conjugation in bacteria and explain the role of F plasmids in bacterial conjugation. (Knowledge of Hfr is not required.)......................................................................................................................................12

(g) Distinguish between structural and regulatory genes. A structural gene is a region of DNA that codes for a protein or RNA molecule that forms part of a structure or has an enzymatic function (e.g. lacY, lacZ, lacA, but excludes lacI). A regulatory gene codes for a specific protein product that regulates the expression of the structural genes (e.g. lacI)......................................12

(h) Distinguish between the concept of repressible and inducible systems of gene regulation using trp and lac operon as examples respectively (attenuation of trp operon is not required).. .12

(i) Describe the concept of a simple operon (using lac operon as an example)...........................12

4. Organisation and Control of Prokaryotic and Eukaryotic Genomes....................................13

(a) Compare the structure and organisation of prokaryotic and eukaryotic chromosomes, in terms of size, packing of DNA, linearity/circularity, presence of introns and type of regulatory sequences....................................................................................................................................13

(b) Describe the structure and function of the portions of eukaryotic DNA that do not encode for protein or RNA, with reference to intron, centromere, telomere, promoter, enhancer and silencer.


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(Knowledge of transposon, satellite DNA, pseudogenes and duplication of segments is not required.)......................................................................................................................................13

(c) Describe the role of telomeres and centromeres....................................................................13

(d) Describe the process and significance of gene amplification within cells, for example in amplification of the genes that code for ribosomes early in cell development, to ensure that sufficient ribosomes can be made to synthesise the proteins that make up the cell....................13

(e) Describe the eukaryotic processing of pre-mRNA in terms of intron splicing, polyadenylation and 5’ capping..............................................................................................................................13

(f) Define control elements and explain how control elements (e.g. promoter, silencer and enhancers) and other factors (e.g. transcription factors, repressors, histone modification and DNA methylation) influence transcription.....................................................................................13

(g) State the various ways in which gene expression may be controlled at translational (e.g. half life of RNA, 5’ capping, initiation of translation) and post-translational level (e.g. biochemical modification and protein degradation)..........................................................................................13

(h) Outline the differences between prokaryotic control of gene expression with the eukaryotic model............................................................................................................................................13

(i) Describe the functions of common proto-oncogenes and tumour suppressor genes (limited to ras and p53) and explain how loss of function mutation and gain of function mutation can contribute to cancer......................................................................................................................13

(j) Describe the development of cancer as a multi-step process..................................................13

5. Genetic Basis for Variation.......................................................................................................14

(a) Explain the terms, locus, allele, dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotype......................................................................................14

(b) Explain how genotype is linked to phenotype and how genes are inherited from one generation to the next via the germ cells or gametes...................................................................14

(c) Explain, with examples, how the environment may affect the phenotype...............................14

(d) Use genetic diagrams to solve problems in dihybrid crosses, including those involving sex linkage, autosomal linkage, epistasis, codominance and multiple alleles....................................14

(e) Use genetic diagrams to solve problems involving test crosses.............................................14

(f) Explain the meaning of the terms linkage and crossing-over and explain the effect of linkage and crossing-over on the phenotypic ratios from dihybrid crosses..............................................14

(g) Explain what is meant by the terms gene mutation and chromosome aberration. For chromosomal aberration, knowledge of numerical [aneuploidy] and structural [translocation, duplication, inversion, deletion] is required...................................................................................14

(h) Describe the differences between continuous and discontinuous variation and explain the genetic basis of continuous variation (many, additive, genes control a characteristic) and discontinuous variation (one or few genes control a characteristic).............................................14

(i) Describe the causes of genetic variation in a population.........................................................14

(j) Describe the interaction between loci (epistasis) and predict phenotypic ratios in problems involving epistasis. (Knowledge of the expected ratio for various types of epistasis is not required; focus of this section is on problem solving.)..................................................................14

(k) Use the chi-squared test to test the significance of differences between observed and expected results...........................................................................................................................14


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6. Cellular Physiology and Biochemistry.....................................................................................15

(a) With reference to the chloroplast structure, explain the light dependent reactions of photosynthesis (no biochemical details are needed but will include the outline of cyclic and non-cyclic light dependent reactions, and the transfer of energy for the subsequent manufacturing of carbohydrates from carbon dioxide).............................................................................................15

(b) Outline the three phases of the Calvin cycle: (i) CO2 uptake (ii) carbon reduction and (iii) ribulose bisphosphate (RuBP) regeneration and indicate the roles of ATP and NADP in the process.........................................................................................................................................15

(c) Discuss limiting factors in photosynthesis and carry out investigations on the effects of limiting factors, such as light intensity, CO2 concentration and temperature, on the rate of photosynthesis..............................................................................................................................15

(d) List and give an overview of the 4 stages of aerobic respiration and indicate where each stage takes place in an eukaryotic cell and mitochondria, and add up the energy captured (as ATP, reduced NAD and FAD) in each stage................................................................................15

(e) Explain the production of a small yield of ATP from anaerobic respiration and the formation of ethanol in yeast and lactate in mammals.....................................................................................15

(f) Compare the storage and structural forms of starch, glycogen and cellulose and their roles in plants and animals........................................................................................................................15

(g) Describe and explain the fluid mosaic model of membrane structure, including an outline of the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins...........................15

(h) Outline the roles and functions of membranes within cells and at the surface of cells. (Knowledge of osmosis, facilitated diffusion, active transport, endocytosis and exocytosis is required.)......................................................................................................................................16

(i) Explain the need for control in organised systems and explain the principles of homeostasis in terms of receptors, effectors, and negative feedback...................................................................16

(j) Explain the need for communication systems within organisms..............................................16

(k) Describe and explain the transmission of an action potential along a myelinated neurone. (The importance of Na+ and K+ ions in the impulse transmission should be emphasised.)........16

(l) Describe the structure of a cholinergic synapse and explain how it functions, including the role of Ca2+ ions.................................................................................................................................16

(m) Explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas.................................................................................................................................16

(n) Explain how the blood glucose concentration is regulated by insulin and glucagon...............16

(o) Describe the main stages of cell signalling – ligand-receptor interaction, signal transduction (inclusive of phosphorylation and signal amplification) and cellular responses. (Limited to an overview of insulin & RTK signalling and glucagon & G-protein signalling. Candidates will be expected to generalise their understanding of these systems in solving problems involving other cell signalling systems.) Advantages and significance of having a cell signalling system may be required........................................................................................................................................16

7. Diversity and Evolution.............................................................................................................17

(a) Explain the binomial nomenclature of a species and hierarchical classification.....................17

(b) Describe the classification of species into taxonomic groups (genus, family, order, class, phylum, kingdom) and explain the various concepts of the species. (Knowledge of biological, ecological, morphological, phylogenetic concepts of species is required.)..................................17


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(c) Explain how species are formed with reference to geographical isolation, physiological isolation and behavioural isolation................................................................................................17

(d) Explain the relationship between classification and phylogeny. (Evolutionary relationships between organisms should be reflected in systematic classification.) Classification is the organisation of species according to particular characteristics. Classification may not take into consideration evolutionary relationship between the species. Phylogeny is the organisation of species according to particular characteristics which takes into consideration the evolutionary relationship between the species.................................................................................................17

(e) Explain why variation is important in selection........................................................................17

(f) Explain, with examples, how environmental factors act as forces of natural selection............17

(g) Explain how natural selection may bring about evolution.......................................................17

(h) Explain why the population is the smallest unit that can evolve.............................................17

(i) Explain how homology (anatomical, embryological and molecular) supports Darwin’s theory of natural selection (with emphasis on descent with modification)...................................................17

(j) Explain how biogeography and the fossil record support the evolutionary deductions based on homologies...................................................................................................................................17

(k) Explain the importance of the use of genome sequences in reconstructing phylogenetic relationships and state the advantages of molecular (nucleotide and amino acid sequences) methods in classifying organisms.................................................................................................17

(l) Explain how genetic variation (including recessive alleles) may be preserved in a natural population.....................................................................................................................................17

(m) Briefly describe the neutral theory of molecular evolution in terms of mutations producing new molecular variants which are selectively neutral. (Knowledge of genetic drift and molecular clock is required.).........................................................................................................................18

B. APPLICATIONS SYLLABUS.....................................................................................................19

8. Isolating, Cloning and Sequencing DNA.................................................................................19

(a) Describe the natural function of restriction enzymes..............................................................19

(b) Explain the formation of recombinant DNA molecule..............................................................19

(c) Outline the procedures for cloning an eukaryotic gene in a bacterial plasmid and describe the properties of plasmids that allow them to be used as DNA cloning vectors.................................19

(d) Explain how eukaryotic genes are cloned using E. coli cells to produce eukaryotic proteins to avoid the problems associated with introns..................................................................................19

(e) Distinguish between a genomic DNA and cDNA library. (Outline of the process of the formation of the libraries and applications of each of the types of library is required.).................19

(f) Outline two important proteins that can be produced by genetic engineering technique (e.g. human growth hormone and insulin)............................................................................................19

(g) Describe the polymerase chain reaction (PCR) and explain the advantages and limitations of this procedure...............................................................................................................................19

(h) Explain how gel electrophoresis is used to analyse DNA.......................................................19

(i) Outline the process of nucleic acid hybridisation and explain how it can be used to detect and analyse restriction fragment length polymorphism (RFLP)...........................................................19


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(j) Explain how RFLP analysis facilitates the process of: i. genomic mapping in terms of linkage mapping; ii. disease detection, e.g. sickle cell anaemia; iii. DNA fingerprinting. (Details of application of gel electrophoresis, PCR and nucleic acid hybridisation in RFLP may be required.)......................................................................................................................................................19

(k) Discuss the goals and implications of the human genome project, including the benefits and difficult ethical concerns for humans. (Knowledge of the technical procedure of the human genome project and sequencing is not required.)........................................................................19

9. Applications of Molecular and Cell Biology............................................................................20

(a) Describe the unique features of zygotic stem cells, embryonic stem cells and blood stem cells, correctly using the terms totipotency (zygotic stem cells which have ability to differentiate into any cell type to form whole organisms and so are also pluripotent and multipotent), pluripotency (embryonic stem cells which have ability to differentiate into almost any cell type to form any organ or type of cell and so are not totipotent but are multipotent) and multipotency (blood stem cells which have ability to differentiate into a limited range of cell types and so are not pluripotent or totipotent)..........................................................................................................20

(b) Explain the normal functions of stem cells in a living organism (e.g. embryonic stem cells and blood stem cells)...........................................................................................................................20

(c) Describe: i. two types of genetic diseases e.g. SCID (severe combined immunodeficiency) and cystic fibrosis; ii. the treatment of SCID and cystic fibrosis, using viral and non-viral gene delivery systems respectively. (Details of manipulation of genes and formation of vectors carrying genes are not required.).................................................................................................20

(d) Explain what are the factors that keep gene therapy from becoming an effective treatment for genetic diseases...........................................................................................................................20

(e) Discuss the social and ethical considerations for the use of gene therapy.............................20

(f) Discuss cloning in plants in terms of plant tissue culture techniques. (Gene cloning in plants using Agrobacterium spp. and gene gun is not required.)............................................................20

(g) Explain the significance of genetic engineering in improving the quality and yield of crop plants and animals in solving the demand for food in the world (e.g. Bt corn, golden rice, GM salmon).........................................................................................................................................20

(h) Discuss the ethical and social implications of genetically modified crop plants and animals (e.g. Bt corn, golden rice and GM salmon)...................................................................................20


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A. CORE SYLLABUS

1. Cellular Functions

Content

• Detailed structure of typical animal and plant cells, as seen under the electron microscope• Outline functions of organelles in plant and animal cells• The structure of carbohydrates, lipids and proteins and their roles in living organisms• Mode of action of enzymes• Replication and division of nuclei and cells• Understanding of chromosome number and variation• Effect of meiosis on chromosome number and variation

Learning Outcomes:

Candidates should be able to:

(a) Describe and interpret drawings and photographs of typical animal and plant cells as seen under the electron microscope, recognising the following membrane systems and organelles: rough and smooth endoplasmic reticulum, Golgi body, mitochondria, ribosomes, lysosomes, chloroplasts, cell surface membrane, nuclear envelope, centrioles, nucleus and nucleolus. (Knowledge of the principles of TEM and SEM are not required.) (For practical assessment, students may be required to operate a light microscope, mount slides and use a graticule.)

(b) Outline the functions of the membrane systems and organelles listed in (a).

(c) Describe the formation and breakage of a glycosidic bond.

(d) Analyse the molecular structure of a triglyceride and a phospholipid, and relate these structures to their functions in living organisms.

(e) Describe the structure of an amino acid and the formation and breakage of a peptide bond.

(f) Explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins, and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) which hold the molecule in shape.

(g) Analyse the molecular structure of a protein with a quaternary structure e.g. haemoglobin, as an example of a globular protein, and of collagen as an example of a fibrous protein, and relate these structures to their functions.

(h) Explain the mode of action of enzymes in terms of an active site, enzyme/substrate complex, lowering of activation energy and enzyme specificity.

(i) Follow the time course of an enzyme-catalysed reaction by measuring rates of formation of products (e.g. using catalase) or rate of disappearance of substrate (e.g. using amylase).


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(j) Investigate and explain the effects of temperature, pH, enzyme concentration and substrate concentration on the rate of enzyme catalysed reactions, and explain these effects.

(k) Explain the effects of competitive and non-competitive inhibitors (including allosteric inhibitors) on the rate of enzyme activity.

(l) Explain the importance of mitosis in growth, repair and asexual reproduction.

(m) Explain the need for the production of genetically identical cells and fine control of replication.

(n) Explain how uncontrolled cell division can result in cancer, and identify causative factors (e.g. genetic, chemical carcinogens, radiation, loss of immunity) which can increase the chances of cancerous growth. (Knowledge that dysregulation of checkpoints of cell division can result in uncontrolled cell division and cancer is required, but detail of the mechanism is not required.)

(o) Describe with the aid of diagrams, the behaviour of chromosomes during the mitotic cell cycle and the associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected)

(p) Explain what is meant by homologous pairs of chromosomes.

(q) Explain the need for reduction division (meiosis) prior to fertilisation in sexual reproduction.

(r) Explain how meiosis and random fertilisation can lead to variation.

(s) Describe, with the aid of diagrams, the behaviour of chromosomes during meiosis, and the associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected, but not the sub-divisions of prophase)

Use the knowledge gained in this section in new situations or to solve related problems.


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2. DNA and Genomics

Content

• DNA – structure and function• Central Dogma – DNA to RNA, RNA to protein

Learning Outcomes:


(a) Describe the structure and roles of DNA and RNA (tRNA, rRNA and mRNA). (Mitochondrial DNA is not required.)

(b) Describe the process of DNA replication and the experimental evidence for semi-conservative replication.

(c) Describe how the information on DNA is used to synthesise polypeptides in prokaryotes and eukaryotes. (Description of the processes of transcription, formation of mRNA from pre-mRNA and translation is required.)

(d) Explain how a change in the sequence of the DNA nucleotide (gene mutation) may affect the amino acid sequence in a protein, and hence the phenotype of the organism e.g. sickle cell anaemia and cystic fibrosis. (Knowledge of substitution, addition, deletion and frameshift mutation may be required.)



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3. Genetics of Viruses and Bacteria

Content

• The Genetics of Viruses• The Genetics of Bacteria

Learning Outcomes:


(a) Discuss whether viruses are living or non-living organisms and explain why viruses are obligate parasites.

(b) Describe the structural components of viruses.

(c) Describe the reproductive cycles of the following virus types: i. bacteriophages that reproduce via a lytic cycle, e.g. T4 phage; ii. bacteriophages that reproduce via a lysogenic cycle, e.g. lambda phage; iii. an enveloped virus e.g. influenza; iv. retroviruses e.g. HIV.

(d) Explain how viral infections cause disease in animals, e.g. mammals, through the disruption of host tissue and functions (e.g. HIV and T helper cells [details of the immune system are not required], influenza and epithelial cells of the respiratory tract).

(e) Describe the structure of a bacterial chromosome including the arrangement of DNA within bacterial cells.

(f) Describe the process of binary fission, transformation, transduction and conjugation in bacteria and explain the role of F plasmids in bacterial conjugation. (Knowledge of Hfr is not required.)

(g) Distinguish between structural and regulatory genes. A structural gene is a region of DNA that codes for a protein or RNA molecule that forms part of a structure or has an enzymatic function (e.g. lacY, lacZ, lacA, but excludes lacI). A regulatory gene codes for a specific protein product that regulates the expression of the structural genes (e.g. lacI).

(h) Distinguish between the concept of repressible and inducible systems of gene regulation using trp and lac operon as examples respectively (attenuation of trp operon is not required).

(i) Describe the concept of a simple operon (using lac operon as an example).



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4. Organisation and Control of Prokaryotic and Eukaryotic Genomes

Content

• The Structure of Eukaryotic Chromatin• Genome Organisation at the DNA level• The Control of Gene Expression• The Molecular Biology of Cancer

Learning Outcomes:


(a) Compare the structure and organisation of prokaryotic and eukaryotic chromosomes, in terms of size, packing of DNA, linearity/circularity, presence of introns and type of regulatory sequences.

(b) Describe the structure and function of the portions of eukaryotic DNA that do not encode for protein or RNA, with reference to intron, centromere, telomere, promoter, enhancer and silencer. (Knowledge of transposon, satellite DNA, pseudogenes and duplication of segments is not required.)

(c) Describe the role of telomeres and centromeres.

(d) Describe the process and significance of gene amplification within cells, for example in amplification of the genes that code for ribosomes early in cell development, to ensure that sufficient ribosomes can be made to synthesise the proteins that make up the cell.

(e) Describe the eukaryotic processing of pre-mRNA in terms of intron splicing, polyadenylation and 5’ capping.

(f) Define control elements and explain how control elements (e.g. promoter, silencer and enhancers) and other factors (e.g. transcription factors, repressors, histone modification and DNA methylation) influence transcription.

(g) State the various ways in which gene expression may be controlled at translational (e.g. half life of RNA, 5’ capping, initiation of translation) and post-translational level (e.g. biochemical modification and protein degradation).

(h) Outline the differences between prokaryotic control of gene expression with the eukaryotic model.

(i) Describe the functions of common proto-oncogenes and tumour suppressor genes (limited to ras and p53) and explain how loss of function mutation and gain of function mutation can contribute to cancer.

(j) Describe the development of cancer as a multi-step process.



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5. Genetic Basis for Variation

Content

• The passage of information from parent to offspring• Genotypes and phenotypes• Dihybrid crosses• Mutations• The effect of genotype and environment on phenotype• Interaction between loci• Linkage and crossing-over

Learning Outcomes:


(a) Explain the terms, locus, allele, dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotype.

(b) Explain how genotype is linked to phenotype and how genes are inherited from one generation to the next via the germ cells or gametes.

(c) Explain, with examples, how the environment may affect the phenotype.

(d) Use genetic diagrams to solve problems in dihybrid crosses, including those involving sex linkage, autosomal linkage, epistasis, codominance and multiple alleles.

(e) Use genetic diagrams to solve problems involving test crosses.

(f) Explain the meaning of the terms linkage and crossing-over and explain the effect of linkage and crossing-over on the phenotypic ratios from dihybrid crosses.

(g) Explain what is meant by the terms gene mutation and chromosome aberration. For chromosomal aberration, knowledge of numerical [aneuploidy] and structural [translocation, duplication, inversion, deletion] is required.

(h) Describe the differences between continuous and discontinuous variation and explain the genetic basis of continuous variation (many, additive, genes control a characteristic) and discontinuous variation (one or few genes control a characteristic).

(i) Describe the causes of genetic variation in a population.

(j) Describe the interaction between loci (epistasis) and predict phenotypic ratios in problems involving epistasis. (Knowledge of the expected ratio for various types of epistasis is not required; focus of this section is on problem solving.)

(k) Use the chi-squared test to test the significance of differences between observed and expected results.



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6. Cellular Physiology and Biochemistry

Content

• The need for energy in living organisms• Photosynthesis as an energy-trapping process• Respiration as an energy-releasing process• Aerobic respiration• Anaerobic respiration• The fluid mosaic model of membrane structure• Homeostasis• Electrical and chemical signalling• Nervous and hormonal control• An overview of cell signalling and communication

o Signal reception and the initiation of transductiono Signal transduction pathwayso Cellular responses to signals

Learning Outcomes:


(a) With reference to the chloroplast structure, explain the light dependent reactions of photosynthesis (no biochemical details are needed but will include the outline of cyclic and non-cyclic light dependent reactions, and the transfer of energy for the subsequent manufacturing of carbohydrates from carbon dioxide).

(b) Outline the three phases of the Calvin cycle: (i) CO2 uptake (ii) carbon reduction and (iii) ribulose bisphosphate (RuBP) regeneration and indicate the roles of ATP and NADP in the process.

(c) Discuss limiting factors in photosynthesis and carry out investigations on the effects of limiting factors, such as light intensity, CO2 concentration and temperature, on the rate of photosynthesis.

(d) List and give an overview of the 4 stages of aerobic respiration and indicate where each stage takes place in an eukaryotic cell and mitochondria, and add up the energy captured (as ATP, reduced NAD and FAD) in each stage.

(e) Explain the production of a small yield of ATP from anaerobic respiration and the formation of ethanol in yeast and lactate in mammals.

(f) Compare the storage and structural forms of starch, glycogen and cellulose and their roles in plants and animals.

(g) Describe and explain the fluid mosaic model of membrane structure, including an outline of the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins.


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(h) Outline the roles and functions of membranes within cells and at the surface of cells. (Knowledge of osmosis, facilitated diffusion, active transport, endocytosis and exocytosis is required.)

(i) Explain the need for control in organised systems and explain the principles of homeostasis in terms of receptors, effectors, and negative feedback.

(j) Explain the need for communication systems within organisms.

(k) Describe and explain the transmission of an action potential along a myelinated neurone. (The importance of Na+ and K+ ions in the impulse transmission should be emphasised.)

(l) Describe the structure of a cholinergic synapse and explain how it functions, including the role of Ca2+ ions.

(m) Explain what is meant by an endocrine gland, with reference to the islets of Langerhans in the pancreas.

(n) Explain how the blood glucose concentration is regulated by insulin and glucagon.

(o) Describe the main stages of cell signalling – ligand-receptor interaction, signal transduction (inclusive of phosphorylation and signal amplification) and cellular responses. (Limited to an overview of insulin & RTK signalling and glucagon & G-protein signalling. Candidates will be expected to generalise their understanding of these systems in solving problems involving other cell signalling systems.) Advantages and significance of having a cell signalling system may be required.



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7. Diversity and Evolution

Content

• Classification• The concept of the species• Variation, natural selection and evolution• The neo-Darwinian revolution• Evidence of evolution

Learning Outcomes:


(a) Explain the binomial nomenclature of a species and hierarchical classification.

(b) Describe the classification of species into taxonomic groups (genus, family, order, class, phylum, kingdom) and explain the various concepts of the species. (Knowledge of biological, ecological, morphological, phylogenetic concepts of species is required.)

(c) Explain how species are formed with reference to geographical isolation, physiological isolation and behavioural isolation.

(d) Explain the relationship between classification and phylogeny. (Evolutionary relationships between organisms should be reflected in systematic classification.) Classification is the organisation of species according to particular characteristics. Classification may not take into consideration evolutionary relationship between the species. Phylogeny is the organisation of species according to particular characteristics which takes into consideration the evolutionary relationship between the species.

(e) Explain why variation is important in selection.

(f) Explain, with examples, how environmental factors act as forces of natural selection.

(g) Explain how natural selection may bring about evolution.

(h) Explain why the population is the smallest unit that can evolve.

(i) Explain how homology (anatomical, embryological and molecular) supports Darwin’s theory of natural selection (with emphasis on descent with modification).

(j) Explain how biogeography and the fossil record support the evolutionary deductions based on homologies.

(k) Explain the importance of the use of genome sequences in reconstructing phylogenetic relationships and state the advantages of molecular (nucleotide and amino acid sequences) methods in classifying organisms.

(l) Explain how genetic variation (including recessive alleles) may be preserved in a natural population.


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(m) Briefly describe the neutral theory of molecular evolution in terms of mutations producing new molecular variants which are selectively neutral. (Knowledge of genetic drift and molecular clock is required.)



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B. APPLICATIONS SYLLABUS

8. Isolating, Cloning and Sequencing DNA

Content

• DNA Cloning (Genetic Engineering)• DNA Analysis and Genomics• Human genome project

Learning Outcomes:


(a) Describe the natural function of restriction enzymes.

(b) Explain the formation of recombinant DNA molecule.

(c) Outline the procedures for cloning an eukaryotic gene in a bacterial plasmid and describe the properties of plasmids that allow them to be used as DNA cloning vectors.

(d) Explain how eukaryotic genes are cloned using E. coli cells to produce eukaryotic proteins to avoid the problems associated with introns.

(e) Distinguish between a genomic DNA and cDNA library. (Outline of the process of the formation of the libraries and applications of each of the types of library is required.)

(f) Outline two important proteins that can be produced by genetic engineering technique (e.g. human growth hormone and insulin).

(g) Describe the polymerase chain reaction (PCR) and explain the advantages and limitations of this procedure.

(h) Explain how gel electrophoresis is used to analyse DNA.

(i) Outline the process of nucleic acid hybridisation and explain how it can be used to detect and analyse restriction fragment length polymorphism (RFLP).

(j) Explain how RFLP analysis facilitates the process of: i. genomic mapping in terms of linkage mapping; ii. disease detection, e.g. sickle cell anaemia; iii. DNA fingerprinting. (Details of application of gel electrophoresis, PCR and nucleic acid hybridisation in RFLP may be required.)

(k) Discuss the goals and implications of the human genome project, including the benefits and difficult ethical concerns for humans. (Knowledge of the technical procedure of the human genome project and sequencing is not required.)



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9. Applications of Molecular and Cell Biology

Content

• Stem cells• The treatment of genetic diseases in humans• Gene therapy• Cloning• Genetic engineering and genetically modified organisms (GMOs)

Learning Outcomes:


(a) Describe the unique features of zygotic stem cells, embryonic stem cells and blood stem cells, correctly using the terms totipotency (zygotic stem cells which have ability to differentiate into any cell type to form whole organisms and so are also pluripotent and multipotent), pluripotency (embryonic stem cells which have ability to differentiate into almost any cell type to form any organ or type of cell and so are not totipotent but are multipotent) and multipotency (blood stem cells which have ability to differentiate into a limited range of cell types and so are not pluripotent or totipotent).

(b) Explain the normal functions of stem cells in a living organism (e.g. embryonic stem cells and blood stem cells).

(c) Describe: i. two types of genetic diseases e.g. SCID (severe combined immunodeficiency) and cystic fibrosis; ii. the treatment of SCID and cystic fibrosis, using viral and non-viral gene delivery systems respectively. (Details of manipulation of genes and formation of vectors carrying genes are not required.)

(d) Explain what are the factors that keep gene therapy from becoming an effective treatment for genetic diseases.

(e) Discuss the social and ethical considerations for the use of gene therapy.

(f) Discuss cloning in plants in terms of plant tissue culture techniques. (Gene cloning in plants using Agrobacterium spp. and gene gun is not required.)

(g) Explain the significance of genetic engineering in improving the quality and yield of crop plants and animals in solving the demand for food in the world (e.g. Bt corn, golden rice, GM salmon).

(h) Discuss the ethical and social implications of genetically modified crop plants and animals (e.g. Bt corn, golden rice and GM salmon).



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