A | B | C | D | E | F | G | H | I | J | K | L | M | |
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1 | Topic | Level | Code | Command term | Assessment Statement | Obj. | Notes | TOK | TOK Connection | Aims | Connection to the aims | ||
2 | 1.1 | Core | 1.1.1 | State | State that error bars are a graphical representation of the variability of data. | 1 | Error bars can be used to show either the range of the data or the standard deviation. | ||||||
3 | 1.1 | Core | 1.1.2 | Calculate | Calculate the mean and standard deviation of a set of values. | 2 | Students should specify the standard deviation (s), not the population standard deviation. Students will not be expected to know the formulas for calculating these statistics. They will be expected to use the standard deviation function of a graphic display or scientific calculator. | Aim7 | Aim 7: Students could also be taught how to calculate standard deviation using a spreadsheet computer program. | ||||
4 | 1.1 | Core | 1.1.3 | State | State that the term standard deviation is used to summarize the spread of values around the mean, and that 68% of the values fall within one standard deviation of the mean. | 1 | For normally distributed data, about 68% of all values lie within ±1 standard deviation (s or σ) of the mean. This rises to about 95% for ±2 standard deviations. | ||||||
5 | 1.1 | Core | 1.1.4 | Explain | Explain how the standard deviation is useful for comparing the means and the spread of data between two or more samples. | 3 | A small standard deviation indicates that the data is clustered closely around the mean value. Conversely, a large standard deviation indicates a wider spread around the mean. | ||||||
6 | 1.1 | Core | 1.1.5 | Deduce | Deduce the significance of the difference between two sets of data using calculated values for t and the appropriate tables. | 3 | For the t-test to be applied, the data must have a normal distribution and a sample size of at least 10. The t-test can be used to compare two sets of data and measure the amount of overlap. Students will not be expected to calculate values of t. Only a two-tailed, unpaired t-test is expected. | TOK | TOK: The scientific community defines an objective standard by which claims about data can be made. | Aim7 | Aim 7: While students are not expected to calculate a value for the t-test, students could be shown how to calculate such values using a spreadsheet program or the graphic display calculator. | ||
7 | 1.1 | Core | 1.1.6 | Explain | Explain that the existence of a correlation does not establish that there is a causal relationship between two variables. | 3 | Aim7 | Aim 7: While calculations of such values are not expected, students who want to use r and r2 values in their practical work could be shown how to determine such values using a spreadsheet program. | |||||
8 | 2.1 | Core | 2.1.1 | Outline | Outline the cell theory. | 2 | Include the following.Living organisms are composed of cells. Cells come from pre-existing cells. Cells are the smallest units of life. | ||||||
9 | 2.1 | Core | 2.1.2 | Discuss | Discuss the evidence for the cell theory. | 3 | TOK: The nature of scientific theories could be introduced here: the accumulation of evidence that allows a hypothesis to become a theory; whether a theory should be abandoned when there is evidence that it does not offer a full explanation; and what evidence is needed for a theory to be adopted or rejected. | ||||||
10 | 2.1 | Core | 2.1.3 | State | State that unicellular organisms carry out all the functions of life. | 1 | Include metabolism, response, homeostasis, growth, reproduction and nutrition. | ||||||
11 | 2.1 | Core | 2.1.4 | Compare | Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit. | 3 | Appreciation of relative size is required, such as molecules (1 nm), thickness of membranes (10 nm), viruses (100 nm), bacteria (1 µm), organelles (up to 10 µm), and most cells (up to 100 µm). The three-dimensional nature/shape of cells should be emphasized. | TOK | TOK: All the biological entities in the above list are beyond our ability to perceive directly. They must be observed through the use of technology such as the light microscope and the electron microscope. Is there any distinction to be drawn between knowledge claims dependent upon observations made directly with the senses and knowledge claims dependent upon observations assisted by technology? | ||||
12 | 2.1 | Core | 2.1.5 | Calculate | Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification. | 2 | Magnification could be stated (for example, ×250) or indicated by means of a scale bar, for example. | Aim7 | Aim 7: The size of objects in digital images of microscope fields could be analysed using graticule baselines and image-processing software. | ||||
13 | 2.1 | Core | 2.1.6 | Explain | Explain the importance of the surface area to volume ratio as a factor limiting cell size. | 3 | Mention the concept that the rate of heat production/waste production/resource consumption of a cell is a function of its volume, whereas the rate of exchange of materials and energy (heat) is a function of its surface area. Simple mathematical models involving cubes and the changes in the ratio that occur as the sides increase by one unit could be compared. | Aim7 | Aim 7: Data logging could be carried out to measure changes in conductivity in distilled water as salt diffuses out of salt–agar cubes of different dimensions. | ||||
14 | 2.1 | Core | 2.1.7 | State | State that multicellular organisms show emergent properties. | 1 | Emergent properties arise from the interaction of component parts: the whole is greater than the sum of its parts. | TOK | TOK: The concept of emergent properties has many implications in biology, and this is an opportunity to introduce them. Life itself can be viewed as an emergent property, and the nature of life could be discussed in the light of this, including differences between living and non-living things and problems about defining death in medical decisions. | ||||
15 | 2.1 | Core | 2.1.8 | Explain | Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others. | 3 | |||||||
16 | 2.1 | Core | 2.1.9 | State | State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. | 1 | |||||||
17 | 2.1 | Core | 2.1.10 | Outline | Outline one therapeutic use of stem cells. | 2 | This is an area of rapid development. In 2005, stem cells were used to restore the insulation tissue of neurons in laboratory rats, resulting in subsequent improvements in their mobility. Any example of the therapeutic use of stem cells in humans or other animals can be chosen. | TOK | TOK: This is an opportunity to discuss balancing the huge opportunities of therapeutic cloning against the considerable risks—for example, stem cells developing into tumours. Another issue is how the scientific community conveys information about its work to the wider community in such a way that informed decisions about research can be made. | Aim8 | Aim 8: There are ethical issues involved in stem cell research, whether humans or other animals are used. Use of embryonic stem cells involves the death of early-stage embryos, but if therapeutic cloning is successfully developed the suffering of patients with a wide variety of conditions could be reduced. Int: Stem cell research has depended on the work of teams of scientists in many countries, who share results and so speed up the rate of progress. However, ethical concerns about the procedures have led to restrictions on research in some countries. National governments are influenced by local, cultural and religious traditions, which vary greatly, and these, therefore, have an impact on the work of scientists. | ||
18 | 2.2 | Core | 2.2.1 | Draw | Draw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote. | 1 | The diagram should show the cell wall, plasma membrane, cytoplasm, pili, flagella, ribosomes and nucleoid (region containing naked DNA). | ||||||
19 | 2.2 | Core | 2.2.2 | Annotate | Annotate the diagram from 2.2.1 with the functions of each named structure. | 2 | |||||||
20 | 2.2 | Core | 2.2.3 | Identify | Identify structures from 2.2.1 in electron micrographs of E. coli. | 2 | |||||||
21 | 2.2 | Core | 2.2.4 | State | State that prokaryotic cells divide by binary fission. | 1 | |||||||
22 | 2.3 | Core | 2.3.1 | Draw | Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell. | 1 | The diagram should show free ribosomes, rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, mitochondrion and nucleus. The term Golgi apparatus will be used in place of Golgi body, Golgi complex or dictyosome. | ||||||
23 | 2.3 | Core | 2.3.2 | Annotate | Annotate the diagram from 2.3.1 with the functions of each named structure. | 2 | |||||||
24 | 2.3 | Core | 2.3.3 | Indentify | Identify structures from 2.3.1 in electron micrographs of liver cells. | 2 | |||||||
25 | 2.3 | Core | 2.3.4 | Compare | Compare prokaryotic and eukaryotic cells. | 3 | Differences should include: naked DNA versus DNA associated with proteins, DNA in cytoplasm versus DNA enclosed in a nuclear envelope, no mitochondria versus mitochondria, 70S versus 80S ribosomes, eukaryotic cells have internal membranes that compartmentalize their functions. | ||||||
26 | 2.3 | Core | 2.3.5 | State | State three differences between plant and animal cells. | 1 | |||||||
27 | 2.3 | Core | 2.3.6 | Outline | Outline two roles of extracellular components. | 2 | The plant cell wall maintains cell shape, prevents excessive water uptake, and holds the whole plant up against the force of gravity. Animal cells secrete glycoproteins that form the extracellular matrix. This functions in support, adhesion and movement. | ||||||
28 | 2.4 | Core | 2.4.1 | Draw | Draw and label a diagram to show the structure of membranes. | 1 | The diagram should show the phospholipid bilayer, cholesterol, glycoproteins, and integral and peripheral proteins. Use the term plasma membrane, not cell surface membrane, for the membrane surrounding the cytoplasm. Integral proteins are embedded in the phospholipid of the membrane, whereas peripheral proteins are attached to its surface. Variations in composition related to the type of membrane are not required. | ||||||
29 | 2.4 | Core | 2.4.2 | Explain | Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes. | 3 | |||||||
30 | 2.4 | Core | 2.4.3 | List | List the functions of membrane proteins. | 1 | Include the following: hormone binding sites, immobilized enzymes, cell adhesion, cell-to-cell communication, channels for passive transport, and pumps for active transport. | ||||||
31 | 2.4 | Core | 2.4.4 | Define | Define diffusion and osmosis. | 1 | Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration. Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration. | Aim7 | Aim 7: Data logging to measure the changes in membrane permeability using colorimeter probes can be used. | ||||
32 | 2.4 | Core | 2.4.5 | Explain | Explain passive transport across membranes by simple diffusion and facilitated diffusion. | 3 | |||||||
33 | 2.4 | Core | 2.4.6 | Explain | Explain the role of protein pumps and ATP in active transport across membranes. | 3 | |||||||
34 | 2.4 | Core | 2.4.7 | Explain | Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane. | 3 | |||||||
35 | 2.4 | Core | 2.4.8 | Describe | Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis. | 2 | |||||||
36 | 2.5 | Core | 2.5.1 | Outline | Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis. | 2 | |||||||
37 | 2.5 | Core | 2.5.2 | State | State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue. | 1 | |||||||
38 | 2.5 | Core | 2.5.3 | State | State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts. | 1 | |||||||
39 | 2.5 | Core | 2.5.4 | Describe | Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase). | 2 | Include supercoiling of chromosomes, attachment of spindle microtubules to centromeres, splitting of centromeres, movement of sister chromosomes to opposite poles, and breakage and re-formation of nuclear membranes. Textbooks vary in the use of the terms chromosome and chromatid. In this course, the two DNA molecules formed by DNA replication are considered to be sister chromatids until the splitting of the centromere at the start of anaphase; after this, they are individual chromosomes. The term kinetochore is not expected. | Aim7 | Aim 7: Students could determine mitotic index and fraction of cells in each phase of mitosis. Individual groups could paste data into a database. Pie charts could be constructed with a graphing computer program. If a graphing computer program is used in DCP for internal assessment, it should be according to the IA and ICT clarifications. | ||||
40 | 2.5 | Core | 2.5.5 | Explain | Explain how mitosis produces two genetically identical nuclei. | 3 | |||||||
41 | 2.5 | Core | 2.5.6 | State | State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis. | 1 | |||||||
42 | 3.1 | Core | 3.1.1 | State | State that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen. | 1 | |||||||
43 | 3.1 | Core | 3.1.2 | State | State that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron and sodium. | 1 | |||||||
44 | 3.1 | Core | 3.1.3 | State | State one role for each of the elements mentioned in 3.1.2. | 1 | Refer to the roles in plants, animals and prokaryotes. | ||||||
45 | 3.1 | Core | 3.1.6 | Explain | Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium. | 3 | Limit the properties to those outlined in 3.1.5. | TOK | TOK: Claims about the “memory of water” have been categorized as pseudoscientific. By what criteria can a claim be judged to be pseudoscientific? | Aim7 | Aim 7: Data logging could be carried out to compare the thermal properties of water with those of other liquids. | ||
46 | 3.2 | Core | 3.2.1 | Distinguish | Distinguish between organic and inorganic compounds. | 2 | Compounds containing carbon that are found in living organisms (except hydrogencarbonates, carbonates and oxides of carbon) are regarded as organic. | ||||||
47 | 3.2 | Core | 3.2.2 | Indentify | Identify amino acids, glucose, ribose and fatty acids from diagrams showing their structure. | 2 | Specific names of amino acids and fatty acids are not expected. | ||||||
48 | 3.2 | Core | 3.2.3 | List | List three examples each of monosaccharides, disaccharides and polysaccharides. | 1 | The examples used should be: glucose, galactose and fructose; maltose, lactose and sucrose; starch, glycogen and cellulose. | ||||||
49 | 3.2 | Core | 3.2.4 | State | State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants. | 1 | |||||||
50 | 3.2 | Core | 3.2.5 | Outline | Outline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids, glycerol and triglycerides; and between amino acids and polypeptides. | 2 | This can be dealt with using equations with words or chemical formulas. | ||||||
51 | 3.2 | Core | 3.2.6 | State | State three functions of lipids. | 1 | Include energy storage and thermal insulation. | ||||||
52 | 3.2 | Core | 3.2.7 | Compare | Compare the use of carbohydrates and lipids in energy storage. | 3 | |||||||
53 | 3.3 | Core | 3.3.1 | Outline | Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate. | 2 | Chemical formulas and the purine/pyrimidine subdivision are not required. Simple shapes can be used to represent the component parts. Only the relative positions are required. | ||||||
54 | 3.3 | Core | 3.3.2 | State | State the names of the four bases in DNA. | 1 | |||||||
55 | 3.3 | Core | 3.3.3 | Outline | Outline how DNA nucleotides are linked together by covalent bonds into a single strand. | 2 | Only the relative positions are required. | ||||||
56 | 3.3 | Core | 3.3.4 | Explain | Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds. | 3 | |||||||
57 | 3.3 | Core | 3.3.5 | Draw | Draw and label a simple diagram of the molecular structure of DNA. | 1 | An extension of the diagram in 3.3.3 is sufficient to show the complementary base pairs of A–T and G–C, held together by hydrogen bonds and the sugar–phosphate backbones. The number of hydrogen bonds between pairs and details of purine/pyrimidines are not required. | TOK | TOK: The story of the elucidation of the structure of DNA illustrates that cooperation and collaboration among scientists exists alongside competition between research groups. To what extent was Watson and Crick’s “discovery” of the three-dimensional structure of DNA dependent on the use of data generated by Rosalind Franklin, which was shared without her knowledge or consent? | ||||
58 | 3.4 | Core | 3.4.1 | Explain | Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase. | 3 | It is not necessary to mention that there is more than one DNA polymerase. | ||||||
59 | 3.4 | Core | 3.4.2 | Explain | Explain the significance of complementary base pairing in the conservation of the base sequence of DNA. | 3 | |||||||
60 | 3.4 | Core | 3.4.3 | State | State that DNA replication is semi-conservative. | 1 | |||||||
61 | 3.5 | Core | 3.5.1 | Compare | Compare the structure of RNA and DNA. | 3 | Limit this to the names of sugars, bases and the number of strands. | ||||||
62 | 3.5 | Core | 3.5.2 | Outline | Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase. | 2 | |||||||
63 | 3.5 | Core | 3.5.3 | Describe | Describe the genetic code in terms of codons composed of triplets of bases. | 2 | |||||||
64 | 3.5 | Core | 3.5.4 | Explain | Explain the process of translation, leading to polypeptide formation. | 3 | Include the roles of messenger RNA (mRNA), transfer RNA (tRNA), codons, anticodons, ribosomes and amino acids. | ||||||
65 | 3.5 | Core | 3.5.5 | Discuss | Discuss the relationship between one gene and one polypeptide. | 3 | Originally, it was assumed that one gene would invariably code for one polypeptide, but many exceptions have been discovered. | TOK | TOK: The way in which theories are modified as related evidence accumulates could be discussed, and whether contrary evidence should cause a theory to be discarded immediately if there are exceptions to it. Where a theory is suddenly and totally abandoned, to be replaced by a different theory, this is known as a paradigm shift. | ||||
66 | 3.6 | Core | 3.6.1 | Define | Define enzyme and active site. | 1 | |||||||
67 | 3.6 | Core | 3.6.2 | Explain | Explain enzyme–substrate specificity. | 3 | The lock-and-key model can be used as a basis for the explanation. Refer to the three-dimensional structure. The induced-fit model is not expected at SL. | ||||||
68 | 3.6 | Core | 3.6.3 | Explain | Explain the effects of temperature, pH and substrate concentration on enzyme activity. | 3 | Aim7-8 | Aim 7: Enzyme activity could be measured using data loggers such as pressure sensors, pH sensors or colorimeters. Aim 8: The effects of environmental acid rain could be discussed. | |||||
69 | 3.6 | Core | 3.6.4 | Define | Define denaturation. | 1 | Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties. Refer only to heat and pH as agents. | ||||||
70 | 3.6 | Core | 3.6.5 | Explain | Explain the use of lactase in the production of lactose-free milk. | 3 | TOK | Int/TOK: Development of some techniques benefits particular human populations and not others because of the natural variation in human characteristics. Lactose intolerance is found in a high proportion of the human population (for example, in Asia) but more rarely among those of European origin. Sometimes a transfer of biotechnology is needed when techniques are developed in one part of the world that are more applicable in another. | |||||
71 | 3.7 | Core | 3.7.1 | Define | Define cell respiration. | 1 | Cell respiration is the controlled release of energy from organic compounds in cells to form ATP. | ||||||
72 | 3.7 | Core | 3.7.2 | State | State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP. | 1 | |||||||
73 | 3.7 | Core | 3.7.3 | Explain | Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. | 3 | Mention that ethanol and carbon dioxide are produced in yeast, whereas lactate is produced in humans. | Aim7 | Aim 7: Data logging using gas sensors, oxygen, carbon dioxide or pH probes could be used. | ||||
74 | 3.7 | Core | 3.7.4 | Explain | Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP. | 3 | |||||||
75 | 3.8 | Core | 3.8.1 | State | State that photosynthesis involves the conversion of light energy into chemical energy. | 1 | |||||||
76 | 3.8 | Core | 3.8.2 | State | State that light from the Sun is composed of a range of wavelengths (colours). | 1 | Reference to actual wavelengths or frequencies is not expected. | ||||||
77 | 3.8 | Core | 3.8.3 | State | State that chlorophyll is the main photosynthetic pigment. | 1 | |||||||
78 | 3.8 | Core | 3.8.4 | Outline | Outline the differences in absorption of red, blue and green light by chlorophyll. | 2 | Students should appreciate that pigments absorb certain colours of light. The remaining colours of light are reflected. It is not necessary to mention wavelengths or the structure responsible for the absorption. | Aim7 | Aim 7: Data logging using colorimeters or light sensors could be used. | ||||
79 | 3.8 | Core | 3.8.5 | State | State that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen. | 1 | |||||||
80 | 3.8 | Core | 3.8.6 | State | State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules. | 1 | |||||||
81 | 3.8 | Core | 3.8.7 | Explain | Explain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase in biomass. | 3 | The recall of details of specific experiments to indicate that photosynthesis has occurred or to measure the rate of photosynthesis is not expected. | ||||||
82 | 3.8 | Core | 3.8.8 | Outline | Outline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis. | 2 | The shape of the graphs is required. The concept of limiting factors is not expected. | Aim7 | Aim 7: Data logging using gas sensors, oxygen, carbon dioxide or pH probes could be used. | ||||
83 | 4.1 | Core | 4.1.1 | State | State that eukaryote chromosomes are made of DNA and proteins. | 1 | The names of the proteins (histones) are not required, nor is the structural relationship between DNA and the proteins. | ||||||
84 | 4.1 | Core | 4.1.2 | Define | Define gene, allele and genome. | 1 | Gene: a heritable factor that controls a specific characteristic. (The differences between structural genes, regulator genes and genes coding for tRNA and rRNA are not expected at SL). Allele: one specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene. Genome: the whole of the genetic information of an organism. | ||||||
85 | 4.1 | Core | 4.1.3 | Define | Define gene mutation. | 1 | The terms point mutation or frameshift mutation will not be used. | ||||||
86 | 4.1 | Core | 4.1.4 | Explain | Explain the consequence of a base substitution mutation in relation to the processes of transcription and translation, using the example of sickle-cell anemia. | 3 | GAG has mutated to GTG causing glutamic acid to be replaced by valine, and hence sickle-cell anemia. | TOK | There are also ethical issues relating to screening of fetuses and abortion of those found to have a genetic disease. TOK: Where a correlation is found, a causal link may or may not be present. The frequency of the sickle-cell allele is correlated with the prevalence of malaria in many parts of the world. In this case, there is a clear causal link. Other cases where there is no causal link could be described as a contrast. There has clearly been natural selection in favour of the sickle-cell allele in malarial areas, despite it causing severe anemia in the homozygous condition. Natural selection has led to particular frequencies of the sickle-cell and the normal hemoglobin alleles, to balance the twin risks of anemia and malaria. | Aim8 | Aim 8: There is a variety of social issues associated with sickle-cell anemia, including the suffering due to anemia, personal feelings if one has either inherited or passed on the sickle-cell allele, questions relating to the desirability of genetic screening for the sickle-cell allele before having children, and the genetic counselling of carriers of the allele. | ||
87 | 4.2 | Core | 4.2.1 | State | State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei. | 1 | |||||||
88 | 4.2 | Core | 4.2.2 | Define | Define homologous chromosomes. | 1 | |||||||
89 | 4.2 | Core | 4.2.3 | Outline | Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells. | 2 | Limit crossing over to the exchange of genetic material between non-sister chromatids during prophase I. Names of the stages are required. | ||||||
90 | 4.2 | Core | 4.2.4 | Explain | Explain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21). | 3 | The characteristics of Down syndrome are not required. | ||||||
91 | 4.2 | Core | 4.2.5 | State | State that, in karyotyping, chromosomes are arranged in pairs according to their size and structure. | 1 | |||||||
92 | 4.2 | Core | 4.2.6 | State | State that karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities. | 1 | TOK | TOK: Various questions relating to karyotyping could be raised, including balancing the risks of side-effects (for example, miscarriage) against the possibility of identifying and aborting a fetus with an abnormality. There are questions about decision-making: who should make the decision about whether to perform karyotyping and allow a subsequent abortion—parents or health-care professionals or both groups? There are also questions about whether or not national governments should interfere with personal freedoms, and whether or not they should be able to ban procedures within the country and possibly also ban citizens travelling to foreign countries where the procedures are permitted. | Aim8 | Aim 8: There are ethical and social issues associated with karyotyping of unborn fetuses because this procedure allows parents to abort fetuses with a chromosome abnormality. There is also evidence that, in some parts of the world, abortion on the basis of gender is carried out. | |||
93 | Core | ||||||||||||
94 | 4.2 | Core | 4.2.7 | Analyse | Analyse a human karyotype to determine gender and whether non-disjunction has occurred. | 3 | Karyotyping can be done by using enlarged photographs of chromosomes. | Aim7 | Aim 7: Online simulations of karyotyping activities are available. | ||||
95 | 4.3 | Core | 4.3.1 | Define | Define genotype, phenotype, dominant allele, recessive allele, codominant alleles, locus, homozygous, heterozygous, carrier and test cross. | 1 | Genotype: the alleles of an organism. Phenotype: the characteristics of an organism. Dominant allele: an allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state. Recessive allele: an allele that only has an effect on the phenotype when present in the homozygous state. Codominant alleles: pairs of alleles that both affect the phenotype when present in a heterozygote. (The terms incomplete and partial dominance are no longer used.) Locus: the particular position on homologous chromosomes of a gene. Homozygous: having two identical alleles of a gene. Carrier: an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele. Test cross: testing a suspected heterozygote by crossing it with a known homozygous recessive. (The term backcross is no longer used.) | ||||||
96 | 4.3 | Core | 4.3.2 | Determine | Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett grid. | 3 | The grid should be labelled to include parental genotypes, gametes, and both offspring genotype and phenotype. | Aim7 | Aim 7: Genetics simulation software is available. | ||||
97 | 4.3 | Core | 4.3.3 | State | State that some genes have more than two alleles (multiple alleles). | 1 | |||||||
98 | 4.3 | Core | 4.3.4 | Describe | Describe ABO blood groups as an example of codominance and multiple alleles. | 2 | |||||||
99 | 4.3 | Core | 4.3.5 | Explain | Explain how the sex chromosomes control gender by referring to the inheritance of X and Y chromosomes in humans. | 3 | |||||||
100 | 4.3 | Core | 4.3.6 | State | State that some genes are present on the X chromosome and absent from the shorter Y chromosome in humans. | 1 |