How do chromosomes determine sex and some diseases

Learning Objectives State where our genetic information is found Interpret the information shown in karyotypes Describe the result of an extra chromosome 21 Show how our sex (boy or girl) is inherited Explain how a recessive genetic disease can be inherited

Karyotype (male) State the total number of chromosomes in each cell Identify the sex chromosomes

Karyotype (female) State the total number of chromosomes in each cell Identify the sex chromosomes

Karyotype (female) Write just a few sentences about Down Syndrome

Inheritance of sex Copy the diagram Explain why it is the sperm that determines the sex of a baby

Genetic disorders Learning Outcomes Describe a number of genetic disorders Analyse pedigree charts showing the inheritance of genetic disorders Research a genetic disorder and present information in the form of a poster

Usher Syndrome

Usher Syndrome R is the healthy allele r is the allele that causes Usher Syndrome An allele is a version of a gene The healthy allele is DOMINANT and the Usher Syndrome is RECESSIVE That means that Rr is healthy

Usher Syndrome Describe the symptoms of Usher syndrome Copy and complete: Usher syndrome is an ________ condition resulting from a defective ________ autosomal gene. Both parents must be ______ and the ________ of each of their children having Usher Syndrome is _____ % recessive carriers 25 probability

Cystic Fibrosis List the symptoms of cystic fibrosis. Explain why you cannot catch cystic from someone else.

Genetically inherited disease All those whose genotypes are not shown are CC Define a carrier for cystic fibrosis? State the genotype of a person with cystic fibrosis. Indicate why the use of the letter C can be confusing. Suggest an alternative letter to use.

Huntington’s Chorea Learning outcomes Describe the symptoms of Huntington’s Chorea Explain the inheritance of Huntington’s Chorea Discuss the controversial issues of those with genetic disorders (or carriers) having children

Huntington’s Disease The disease damages some of the nerve cells in the brain, causing deterioration and gradual loss of function of these areas of the brain. This can affect movement, judgement) and behaviour. It is a dominant gene so only one copy of the gene is required to result in Huntington’s Disease. People can start to show the symptoms of Huntington's disease at almost any age, but most will develop problems between the ages of 35 and 55. This is often after they have had children which is why the gene persists through successive generations.

Woody Guthrie is perhaps the most famous person to suffer from Huntington’s Disease.

Woody Guthrie Woody inherited the disease from his mother, Nora His father, Charles Edward, did not have Huntington’s Disease Woody Guthrie Woody inherited the disease from his mother, Nora Let H be the allele for Huntington’s Disease. Produce a genetic diagram to show how Woody inherited the disease.

Huntington’s Chorea Normal Huntington’s Huntington’s Chorea is caused by a dominant/recessive allele found on chromosome 4/X chromosome. It is controversial as to whether someone with a genetic disorder should have children. Write a short paragraph discussing the issues and arguments. Who should make the decision? Hope of medical developments? Screening of embryos? The value of a shortened life? H = Huntington’s h = healthy

Huntington’s Disease H h h h Nora Huntington’s Charles Edward Normal Parental Phenotype Genotype Gametes Punnet square Ratio 1 Huntington’s : 1 normal Hh hh H h h h

Huntington’s Chorea

Learning Objectives Use counters to determine the outcomes of genetic crosses Show the importance of there being a large number of offspring in obtaining reliable genetic ratios Distinguish between homozygous and heterozygous Suggest possible genotypes for dominant and recessive phenotpes Use punnet squares to determine phenotypic ratios Give the genotypic and phenotypic outcomes as percentages

Crossing Tt with Tt (Two tall pea plants) Egg Sperm Genotype Phenotype

Crossing Tt with Tt (Two tall pea plants) Group Tall Short 1 8 2 7 3 4 5 6 9 Totals 48 12 This gives an approximate ratio of: 4:1

Crossing Tt with tt (Tall vs short) Egg Sperm Genotype Phenotype

Crossing Tt with tt (Tall vs short) Group Tall Short 1 7 3 2 4 6 5 9 Totals 31 29 This gives an approximate ratio of: 1:1

Mendel’s results

Crossing Tt with tt (Tall vs short) Parent 1 Parent 2 Ratio Tall TT All tall TT Tall Tt All tall TT/Tt Short tt All tall Tt 3 tall : 1 short TT/Tt/Tt/tt 1 Tall : 1 short Tt/tt All short tt If we know the genotypes of the parents we can predict the ratios of the offspring By looking at the phenotypic ratios of the offspring, we can deduce (work out) the genotypes of the parents

Learning objectives Research a science topic Communicate scientific ideas Present information using visual impact

Posters – research and communication Tay-sachs Giordan Kathleen Huntington’s Chorea Cystic Fibrosis Chloe Casey Phenylketonurea Haemophilia Catriona Charlotte Grant Duchenne Muscular Dystrophy Danny Emily Usher Syndrome Kyle Maciej Sickle Cell Disease Issac Alec