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CLIL MODULE – DNA and GENETIC DISEASES 2° Liceo Scientifico Istituto Sant’Anna Prof.ssa Elena Tibaldi AS 2013-2014 1 To know: • concept of chromosome, gene and allele • concept of homozygous and heterozygous Content objectives To be able to: • predict the genotype and phenotype of the offspring using Punnett square To be aware of: • the effect of genetic mutations in the onset of genetic disorders • the effect of non-disjunction during meiosis • recent discoveries on gene therapy Language objectives Expand knowledge of content-specific vocabulary Working on scientific words: use of prefixes and suffixes to convey precise meaning Describe a process/an experiment and motivate results Passive forms of the verbs Link words and sequencers Prerequisites The structure of DNA Æ see review slide Cell cycle and division; mitosis and meiosis Æ see review slides Task-based activity Groupwork: powerpoint presentation Timing Second term; II year Classes: IIA and IIB Liceo 2 GLOSSARY Æ CONTENT-SPECIFIC VOCABULARY TERM (translation) DEFINITION Heredity / Inheritance ( ) Genetic information is passed on from parents to their offspring Chromosome ( Thread-like structure made up of DNA and proteins ) Gene ( Sequence of DNA coding for a protein ) Gamete ( ) Male cell (sperm) or female cell (egg) are produced in the gonads and join together (fertilization) to form a new organism (zygote) ) Alternative forms of a gene which are found on a chromosome. It can be dominant (A) or recessive (a) Allele ( Genotype ( ) Phenotype ( ) The genotype is the actual genetic make up of an individual and derives from the combination of alleles of the genes from both parents. The phenotype is what that individual looks like. The phenotype is the visible expression of genes. 3 BRAINSTORMING Æ COMPARE INHERITED HUMAN TRAITS Other human genetic traits Dark/blond hair Curly/straight hair Dark/light-coloured skin 4 HUMAN TRAITS DEPEND ON THE INFORMATION CONTAINED IN THE DNA DNA is a double helical structure consisting of two filaments (strands) made of nucleotides. The two strands are complementary in nucleotidic sequence (Adenine - Thymine) and (Cytosine - Guanine) and are held together by hydrogen bonds between the complementary bases of the two strands. 5 LAB ACTIVITY: DNA EXTRACTION FROM FRUIT Materials: • 100g of fruit pulp (½ banana /3 kiwis / ½ pear /some strawberries) • salt • liquid detergent (not from concentrate) 1-2 • Pineapple juice • Plastic pipettes • 5ml syringes • plastic dishes, forks, knives and spoons • Beakers and cylinders •Test tubes • 95% ice-cold alcohol Experimental procedure: 1. Peel the fruit and place it in a plastic dish 2. Using knife and fork, mash the fruit pulp for several minutes 3. In a 250 ml beaker prepare the extraction solution by adding: 3g (½ tablespoon) of salt 90 ml distilled water 10 ml liquid detergent 3 6 http://www.funsci.com/fun3_en/dna/dnaen.htm 4. Add the mashed pulp into the extraction solution and stir for 10 minutes without making bubbles. 4 5. Filter the solution through a paper filter into a 100ml beaker. Make sure the top part of the filter is folded over the top of the beaker and that the bottom of the filter does not touch the bottom of the cup 6. Put 5ml of the filtrate into a test tube. 5 7. Add 1ml of pineapple juice. Mix 2-3 minutes. 8. Slowly add 6ml of ice-cold alcohol. 9. Wait a few minutes until you see the DNA coming out of solution as a cotton thread in the tube. 6-7 10. Collect the DNA with a toothpick 8 9-10 7 http://www.funsci.com/fun3_en/dna/dnaen.htm AT THE END OF THE LAB ACTIVITY, ANSWER THE FOLLOWING QUESTIONS 1. What is the purpose of mashing up the fruit pulp?................................................ 2. What does the extraction solution do?................................................................... 3. What is the purpose of the detergent in the extraction solution? To destroy cell membrane To digest fruit fibers To make DNA precipitation 4. Why do we filter the solution?............................................................................... 5. What is the purpose of adding the pineapple juice?.............................................. 6. What happens when you add the alcohol to the filtrate?..................................... 7. What does the DNA look like?............................................................................... 8. Why are bubbles formed during ethanol precipitation? Bromeline contained in the pineapple juice Low temperature of ethanol Presence of detergent 9. Place the following steps of the experimental procedure in the correct order digestion of proteins ethanol precipitation break down of cell membranes 8 DNA IS ORGANIZED IN CHROMOSOMES 9 WORD STUDY: THE CHROMOSOME The prefix CHROM- is referred to colour Exercise Æ find out the meaning of the following terms: • Chromatin: ........................................................................ • Sister chromatids: .......................................................... The prefix or suffix SOME is referred to body. Exercise Æ find out the meaning of the following terms: • Nucleosome: .......................................................................................................................................... • Lysosome: .............................................................................................................................................. • Centrosome: ............................................................................................................................................ • Somatic cell: ........................................................................................................................................ CHROMOSOME = stained (=coloured) body Walther Flemming (1843-1905), a German biologist and founder of cytogenetics, was the first scientist that stained the chromatin in the nucleus using aniline dye. He correlated the chromatin with the threadlike structures that were lately named chromosomes. Other dyes for nuclear staining are commonly used in 10 the lab: Giemsa, methylene blue and acridine orange. GUESS WHO ...? .......................................................... discovered the chromosomes and the process of mitosis. Walter Flemming .......................................................... discovered the structure of DNA. Gregor Mendel .......................................................... identified laws of inheritance working with pea plants. James Watson and Francis Crick 11 DEFECTS IN THE NUMBER OF CHROMOSOMES Non-disjunction during meiosis causes the altered number of chromosomes in the gamete. Here a few examples of chromosomal defects. 1) Defects in the number of sexual chromosomes: individuals can live normally, but are generally sterile. • Turner syndrome (XO) Æ female with only one X chromosome • Klinefelter syndrome (XXY) Æ male, with two X chromosomes 2) Defects in the number of autosomes: in the majority of cases, defects in the number of autosome causes abortion; the only possibility of survival is: • Edwards syndrome (trisomy of chr. 18) Æ 90% of affected children die within the first six months because of heart damage and failure. • Patau syndrome (trisomy of chr. 13) Æ affected children die within the first three months because of damage to the nervous system and heart failure. • Down syndrome (trisomy of chr.21) Æ affected children show mental retardation and delay in physical growth. Many children with Down syndrome are educated in regular school classes while others require specialised educational facilities. Education and proper care has been shown to improve quality of life significantly. Many adults with Down Syndrome are able to work at paid employment in the community, while others require a more sheltered work environment. Life expectancy depends on the severity of the disease. 12 TRISOMY 21: THE STORY OF DOWN SYNDROME Dr. John Langdon Down was a British medical doctor who first observed children with a special kind of mental disability and common physical characteristics and published his findings in 1866. In July 1958, Dr. Jerome Lejeune, while studying chromosomes linked to Down syndrome, discovered the existence of an additional chromosome on the 21st pair. He therefore renamed the condition trisomy 21 to accurately describe the genetic abnormality. For the first time Dr. Lejeune had established a link between an intellectual disability and its genetic cause. GENETIC DISORDERS: MUTATIONS ON A SINGLE GENE AUTOSOMAL DOMINANT = Mutation occurs in the dominant allele (A*)Æ Both homozygous dominant (A*A*) and heterozygous (AA*) individuals are sick Ex. Huntington’s disease X-LINKED DOMINANT = Mutation occurs in an allele on the X chromosome (X*): X*X* Æ homozygous female, sick X*X Æ heterozygous female, sick X*Y Æ male, sick Ex. Rett syndrome AUTOSOMAL RECESSIVE = Mutation occurs in the recessive allele (a*) Æ Homozygous recessive (a*a*) individual is sick; heterozygous (Aa*) is carrier. Ex. Albinism; sickle-cell anemia; cystic fibrosis; Tay-Sachs syndrome. X-LINKED RECESSIVE = Mutation occurs in an allele on the X chromosome (X*): X*X* Æ homozygous female, sick X*X Æ heterozygous female, carrier X*Y Æ male, sick Ex. Duchenne muscolar dystrophy; haemophilia; color blindness (daltonism) Y-LINKED = Mutation occurs in an allele on the Y chromosome (Y*): XY Æ healthy male XY* Æ sick male 14 THE SICKLE-CELL ANEMIA HbAHbS HbAHbA HbAHbS HbAHbS HbSHbS The heterozygous HbAHbS shows an advantage in case of malaria: Plasmodium falciparum does not live in sickle cell, therefore heterozygous individuals are not affected by malaria. 15 ALBINISM Æ NOT ONLY A HUMAN CONDITION Albinism (from Latin “Albus” = white) is caused by a genetic mutation of a gene coding for an enzyme involved in the production of melanin in skin, eyes and hair. 16 COLOUR BLINDNESS (DALTONISM) Colour blindness or colour vision deficiency is the inability or decreased ability to see colours, or perceive colour differences, under normal lighting conditions. The English chemist John Dalton published the first scientific paper on this subject in 1798, "Extraordinary facts relating to the vision of colours", after having become aware of his own colour blindness. Because of Dalton's work, the general condition has been called daltonism. Vision is allowed by photoreceptors called cone cells (active in normal daylight) and rod cells (active in low light). Colour blindness is caused by mutations of genes involved in colour vision which are present on the Xchromosome. COLOUR BLINDNESS TEST 17 HAEMOPHILIA AND THE ENGLISH ROYAL FAMILY Haemophilia is caused by a mutation in the gene coding for the clotting factor VIII. Such mutation causes problems during blood clotting after injures. Since this recessive gene is encoded on the X chromosome, males can be healthy or sick; females can be carriers. 18 stemcells.nih.gov/info/Regenerative_Medicine/Pages/2006Chapter4.aspx GENE THERAPY: A SOLUTION FOR GENETIC DISEASES? TASK-BASED ACTIVITY Aim of the activity Each group elaborates a powerpoint presentation in which the outstanding results on topics related to genetics are described and presented it to the whole class. Procedure Students, in small groups, should choose one of the following topic and elaborate a powerpoint presentation on: 9 Information about scientists such as Lejeune, Watson and Crick, Flemming or others related to genetics or medicine 9 Description of a chromosomal or a genetic disorder 9 Recent discoveries on gene therapy Students can find the above information by consulting science textbooks, other books, internet. Bibliography and sitography must be included in the presentation. Language skills Oral activity Æ speaking in small groups / with whole class Written activity Æ powerpoint presentation Use of content-specific language 20 BIBLIOGRAPHY and SITOGRAPHY Books and textbooks: • Gateway to Science – Thompson Heinle • Biology. Course companion – Allott and Mindorff- Oxford • Science. Oxford content and language support – Kauser and O’Donoghue - Oxford • Science – Keith Kelly – Macmillan Vocabulary Practice Series – Macmillan • Biology for IB diploma – Standard and high level – Andrew Allott – Oxford • Edexcel IGCSE Biology – Bradfield and Potter- Pearson Websites http://www.bbc.co.uk/schools/gcsebitesize/science/ http://www.cellsalive.com/cells/3dcell.htm http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/cells http://www.bbc.co.uk/scotland/learning/bitesize/standard/biology/investigating_cells/ cells_and_diffusion_rev2.shtml http://www.cellsalive.com/cell_cycle.htm http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokine sis.html http://www.cellsalive.com/mitosis.htm http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/celldivision/ http://www.cellsalive.com/puzzles/mitosis/index.html http://science.education.nih.gov/supplements/nih1/cancer/activities/activity2_animatio ns.htm 21 https://wikispaces.psu.edu/display/bio110/Home